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Islam MT, Chen Y, Seong D, Verhougstraete M, Son YJ. Effects of recirculation and air change per hour on COVID-19 transmission in indoor settings: A CFD study with varying HVAC parameters. Heliyon 2024; 10:e35092. [PMID: 39170199 PMCID: PMC11336487 DOI: 10.1016/j.heliyon.2024.e35092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Revised: 06/08/2024] [Accepted: 07/23/2024] [Indexed: 08/23/2024] Open
Abstract
COVID-19 has already claimed over 7 million lives and has infected over 775 million people globally [1]. SARS-CoV-2, the virus that causes Covid-19, spreads primarily through droplets from infected people's airways, rendering Heating, Ventilation, and Air Conditioning (HVAC) systems critical in controlling infection risk levels in the indoor environment. To understand the dynamics of exhaled droplets and aerosols and the percentage of particles that are inhaled, escaped, recirculated, or trapped on different surfaces for a variety of environmental settings, we have presented our findings from the Computational Fluid Dynamics (CFD) modeling to investigate the impact of changing HVAC parameters in this paper. When combined with the spatial and temporal distribution of droplets, this method can be used to assess the potential risk and strengthen resilience. This finding demonstrates the viability and usefulness of CFD for modeling the distribution and dynamics of droplets and aerosols in confined environments. Our study demonstrates that raising the Air Change per Hour (ACH) from 2 to 8 reduces the risk of particle inhalation by nearly 70 %. Additionally, limiting the amount of air recirculation or increasing the amount of fresh air helps to reduce the number of airborne particles in an indoor space. To reduce the potential for respiratory droplet-related transmission and to provide relevant recommendations to the appropriate authority, the same computational approach could be applied to a wide range of ventilated indoor environments such as public buses, restaurants, exhibitions, and theaters.
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Affiliation(s)
- Md Tariqul Islam
- School of Industrial Engineering, Purdue University, West Lafayette, IN, USA
| | - Yijie Chen
- Systems and Industrial Engineering, University of Arizona, Tucson, AZ, USA
| | - Dahae Seong
- Community, Environment & Policy Department, University of Arizona, Tucson, AZ, USA
| | - Marc Verhougstraete
- Community, Environment & Policy Department, University of Arizona, Tucson, AZ, USA
| | - Young- Jun Son
- School of Industrial Engineering, Purdue University, West Lafayette, IN, USA
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2
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Seyedzadeh H, Craig J, Khosronejad A. On the efficacy of facial masks to suppress the spreading of pathogen-carrying saliva particles during human respiratory events: Insights gained via high-fidelity numerical modeling. MEDICAL RESEARCH ARCHIVES 2024; 12:5441. [PMID: 38911991 PMCID: PMC11192503 DOI: 10.18103/mra.v12i5.5441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/25/2024]
Abstract
Respiratory fluid dynamics is integral to comprehending the transmission of infectious diseases and the effectiveness of interventions such as face masks and social distancing. In this research, we present our recent studies that investigate respiratory particle transport via high-fidelity large eddy simulation coupled with the Lagrangian particle tracking method. Based on our numerical simulation results for human respiratory events with and without face masks, we demonstrate that facial masks could significantly suppress particle spreading. The studied respiratory events include coughing and normal breathing through mouth and nose. Using the Lagrangian particle tracking simulation results, we elucidated the transport pathways of saliva particles during inhalation and exhalation of breathing cycles, contributing to our understanding of respiratory physiology and potential disease transmission routes. Our findings underscore the importance of respiratory fluid dynamics research in informing public health strategies to reduce the spread of respiratory infections. Combining advanced mathematical modeling techniques with experimental data will help future research on airborne disease transmission dynamics and the effectiveness of preventive measures such as face masks.
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Affiliation(s)
- Hossein Seyedzadeh
- Department of Civil Engineering, Stony Brook University, Stony Brook, NY 11794, USA
| | - Jonathan Craig
- Department of Civil Engineering, Stony Brook University, Stony Brook, NY 11794, USA
| | - Ali Khosronejad
- Department of Civil Engineering, Stony Brook University, Stony Brook, NY 11794, USA
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3
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Kusuluri R, Mirikar D, Palanivel S, Arumuru V. Risk assessment of airborne virus transmission in an intensive care unit due to single and sequential coughing. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2024; 44:54-69. [PMID: 37038233 DOI: 10.1111/risa.14133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 01/19/2023] [Accepted: 03/02/2023] [Indexed: 06/19/2023]
Abstract
The virus causing COVID-19 has constantly been mutating into new variants. Some of them are more transmissive and resistant to antibiotics. The current research article aims to examine the airborne transmission of the virus expelled by coughing action in a typical intensive care unit. Both single and sequential coughing actions have been considered to get closer to practical scenarios. The objective is to assess the effectiveness of air change per hour (ACH) on the risk of infection to a healthcare person and how the air change rate influences the dispersion of droplets. Such a study is seldom reported and has significant relevance. A total of four cases were analyzed, of which two were of sequential cough. When the ACH is changed from 6 to 12, the average particle residence time is reduced by ∼7 s. It is found that the risk of infection in the case of sequential cough will be relatively low compared to a single cough if the outlet of the indoor environment is placed above the patient's head. This arrangement also eliminates the requirement of higher ACH, which has significance from an energy conservation perspective.
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Affiliation(s)
- Rajendra Kusuluri
- Applied Fluids Group, School of Mechanical Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar, India
| | - Dnyanesh Mirikar
- Applied Fluids Group, School of Mechanical Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar, India
| | - Silambarasan Palanivel
- Applied Fluids Group, School of Mechanical Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar, India
| | - Venugopal Arumuru
- Applied Fluids Group, School of Mechanical Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar, India
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4
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Liu Y, Cheng X, Tang D, Wang X. Optimization of cabin seating arrangement strategies based on the Wells-Riley risk theory. PLoS One 2023; 18:e0294345. [PMID: 37983230 PMCID: PMC10659163 DOI: 10.1371/journal.pone.0294345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Accepted: 10/28/2023] [Indexed: 11/22/2023] Open
Abstract
Civil aviation transport is an important source of global respiratory disease spread due to the closely-spaced environment. In order to reduce the probability of infection of passengers, an improved Wells-Riley model for cabin passenger risk assessment have been given in this work, the cabin ventilation and passenger nose and mouth orientation were considered. The model's effectiveness has been verified with published data. Finally, how the load factor and use of an empty seat scheme are associated with the number of infected people was assessed. The results demonstrated that the number of infected people positively correlates with the passenger load factor, and the most suitable load factor can be determined by controlling the final number of infected people with the condition of the epidemic situation in the departure city. Additionally, infection risk was found to be lower among passengers in window seats than in those in aisle seats and middle seats, and keeping empty seats in the middle or aisle could reduce the cabin average probability of infection by up to 37.47%. Using the model developed here, airlines can determine the optimal load factor threshold and seating arrangement strategy to improve economic benefits and reduce the probability of passenger infection.
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Affiliation(s)
- Yanxi Liu
- Department of Airport, School of Transportation Science and Engineering, Civil Aviation University of China, Tianjin, China
| | - Xuan Cheng
- Department of Airport, School of Transportation Science and Engineering, Civil Aviation University of China, Tianjin, China
| | - Dengzhao Tang
- Department of Airport, School of Transportation Science and Engineering, Civil Aviation University of China, Tianjin, China
| | - Xinyue Wang
- Department of Airport, School of Transportation Science and Engineering, Civil Aviation University of China, Tianjin, China
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5
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Okajima J, Kato M, Hayakawa A, Iga Y. Investigation of bimodal characteristics of the droplet size distribution in condensation spray. Sci Rep 2023; 13:12006. [PMID: 37491517 PMCID: PMC10368728 DOI: 10.1038/s41598-023-39087-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2023] [Accepted: 07/20/2023] [Indexed: 07/27/2023] Open
Abstract
To understand the generation process of airborne droplets during exhalation, this study investigates the mechanism of bimodal characteristics of the size distribution of droplets generated in a condensed spray flow. The phase change process in the condensed spray flow was estimated based on the droplet size distribution measured by a phase Doppler particle analyzer and the temperature distribution measured by a thermistor. On the central axis, the size distribution was unimodal in the spray interior. In contrast, bimodality of the size distribution at the outer edge of the spray flow was observed. At the edge of the spray flow, a large temperature gradient was formed. This indicates that condensation actively occurred at the outer edge. For the same reason as outlined above, condensation did not progress at the spray center because of the consumption of water vapor at the outer edge by the condensation, and the droplet diameter did not change significantly. Hence, owing to the difference in the local phase change process between the center and outer edge of the spray, large and small droplets can exist simultaneously in the middle region. As a result, the size distribution of the condensation spray is bimodal.
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Affiliation(s)
- Junnosuke Okajima
- Institute of Fluid Science, Tohoku University, Sendai, 980-8579, Japan.
| | - Mitsuki Kato
- Institute of Fluid Science, Tohoku University, Sendai, 980-8579, Japan
- Mechanical Engineering Division, Tohoku University, Sendai, 980-8579, Japan
| | - Akihiro Hayakawa
- Institute of Fluid Science, Tohoku University, Sendai, 980-8579, Japan
| | - Yuka Iga
- Institute of Fluid Science, Tohoku University, Sendai, 980-8579, Japan
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6
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Arumuru V, Kusuluri R, Mirikar D. Role of face masks and ventilation rates in mitigating respiratory disease transmission in ICU. Sci Rep 2023; 13:11124. [PMID: 37429928 DOI: 10.1038/s41598-023-38031-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 07/01/2023] [Indexed: 07/12/2023] Open
Abstract
Indoor environments are major contributing locations where the respiratory virus transmission occurs. Higher air change rate (ACH) values (up to 12) have been recommended in hospital environments to reduce virus transmission. In the present study, the Large Eddy Simulation (LES) data of particle transport in a typical intensive care unit (ICU) is used to calculate the infection risk in close proximity interaction. Three different ACH (6, 9, 12) rates with face masks and one case with a healthy person wearing a face shield are considered. The average resident time of the droplets in the ICU is calculated to find the optimal ACH rate. Of the different types of masks analyzed in the present study, the triple-layer mask has shown the most resistance ([Formula: see text] probability of infection) to the penetration of virus-laden droplets, while the single-layer mask has shown the highest risk of infection (up to [Formula: see text]. The results show that the ACH rate has little effect on close proximity transmission. The ACH 9 case provided optimal value for the particle removal, while the ACH 12 has inferior performance to that of ACH 9. From an energy consumption view, our results recommend not using higher ACH in similar indoor environments. Inside indoor environments, it is advised to wear a three-layer face mask and face shield to reduce the risk of infection.
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Affiliation(s)
- Venugopal Arumuru
- Applied Fluids Group, School of Mechanical Sciences, Indian Institute of Technology, Bhubaneswar, 752050, India.
| | - Rajendra Kusuluri
- Applied Fluids Group, School of Mechanical Sciences, Indian Institute of Technology, Bhubaneswar, 752050, India
| | - Dnyanesh Mirikar
- Applied Fluids Group, School of Mechanical Sciences, Indian Institute of Technology, Bhubaneswar, 752050, India
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7
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Nazari A, Taghizadeh-Hesary F. Numerical investigation of airborne infection risk in an elevator cabin under different ventilation designs. PHYSICS OF FLUIDS 2023; 35. [DOI: 10.1063/5.0152878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/21/2024]
Abstract
Airborne transmission of SARS-CoV-2 via virus-laden aerosols in enclosed spaces poses a significant concern. Elevators, commonly utilized enclosed spaces in modern tall buildings, present a challenge as the impact of varying heating, ventilation, and air conditioning (HVAC) systems on virus transmission within these cabins remains unclear. In this study, we employ computational modeling to examine aerosol transmission within an elevator cabin outfitted with diverse HVAC systems. Using a transport equation, we model aerosol concentration and assess infection risk distribution across passengers' breathing zones. We calculate the particle removal efficiency for each HVAC design and introduce a suppression effect criterion to evaluate the effectiveness of the HVAC systems. Our findings reveal that mixing ventilation, featuring both inlet and outlet at the ceiling, proves most efficient in reducing particle spread, achieving a maximum removal efficiency of 79.40% during the exposure time. Conversely, the stratum ventilation model attains a mere removal efficiency of 3.97%. These results underscore the importance of careful HVAC system selection in mitigating the risk of SARS-CoV-2 transmission within elevator cabins.
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Affiliation(s)
- Ata Nazari
- University of Tabriz, Department of Mechanical Engineering 1 , Tabriz, Iran
| | - Farzad Taghizadeh-Hesary
- ENT and Head and Neck Research Center and Department, The Five Senses Health Institute, School of Medicine, Iran University of Medical Sciences 5 , Tehran, Iran
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8
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Sanguinetti A, DePew A, Hirschfelt K. Vehicle Design Strategies to Reduce the Risk of COVID-19 Transmission in Shared and Pooled Travel: Inventory, Typology, and Considerations for Research and Implementation. TRANSPORTATION RESEARCH RECORD 2023; 2677:641-655. [PMID: 38603437 PMCID: PMC9852963 DOI: 10.1177/03611981221141631] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/13/2024]
Abstract
The global COVID-19 pandemic has given rise to a plethora of ideas for modifying and redesigning public transportation and shared mobility vehicles to protect workers and riders from contracting the disease while traveling. This research seeks to inventory these strategies, and to organize and distill them in a way that enables researchers, policymakers, and public transport and mobility service operators to more systematically and efficiently evaluate them. Through literature search and analysis, the COVID-19 risk-mitigating vehicle design (CRVD) typology was developed, articulating 12 categories of strategies (e.g., Seating Configuration, Barriers) and 12 mechanisms (e.g., physical distancing, physical separation) by which the strategies may reduce COVID-19 spread. A secondary contribution of this research is to gather opinions of experts in fields related to COVID-19 and its transmission, about the identified CRVD strategies and mitigation mechanisms. The typology and expert opinions serve as a launching point for further innovation and research to evaluate the effectiveness of CRVD strategies and their relationship to user preferences and travel behavior, within and beyond the current context. Public transport and shared mobility service operators can use the CRVD typology as a reference, in conjunction with industry guidance and emerging research on strategy effectiveness, to aid decision-making in their continued response to the pandemic as well as for future planning.
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Affiliation(s)
- Angela Sanguinetti
- Institute of Transportation Studies,
University of California, Davis, CA
| | - Ashley DePew
- Institute of Transportation Studies,
University of California, Davis, CA
| | - Kate Hirschfelt
- Institute of Transportation Studies,
University of California, Davis, CA
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9
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Liu Z, Wu J, Yang G, Zhang X, Dai Z. A numerical study of COVID-19-laden droplets dispersion in aircraft cabin ventilation system. Heliyon 2023; 9:e13920. [PMID: 36851973 PMCID: PMC9946782 DOI: 10.1016/j.heliyon.2023.e13920] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2022] [Revised: 02/14/2023] [Accepted: 02/15/2023] [Indexed: 02/25/2023] Open
Abstract
Ventilation systems for aircraft cabins are mainly used to maintain a comfortable environment in the cabin and ensure the health of passengers. This study evaluates the decontamination performance of two cabin ventilation systems, the displacement ventilation (DV) system and the mixing ventilation (MV) system, in preventing contamination by virus (COVID-19)-laden droplets. The Euler-Lagrange method was used to computationally model droplet dispersion of different diameters and their behavior in the two systems was contrastively analyzed. Statistics on droplet suspension ratios and duration as well as the infection probability of each passenger were also computed. It was found that11.07% fewer droplet remained suspended in the DV system were than those in the MV system 10s from droplet release. In addition, the number of droplets extracted from the exhausts in the DV system was 13.15% more than the MV system at the 400s mark. In the DV system, higher ambient wind velocities were also found to locally increase infection probability for passengers in certain locations.
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Affiliation(s)
- Zhuxun Liu
- School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Jingyi Wu
- School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China,Corresponding author.
| | - Guang Yang
- School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Xintai Zhang
- COMAC Shanghai Aircraft Design & Research Institute, Shanghai 201203, China
| | - Zheng Dai
- COMAC Shanghai Aircraft Design & Research Institute, Shanghai 201203, China
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10
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Schmeling D, Shishkin A, Schiepel D, Wagner C. Numerical and experimental study of aerosol dispersion in the Do728 aircraft cabin. CEAS AERONAUTICAL JOURNAL 2023; 14:509-526. [PMID: 36819984 PMCID: PMC9930724 DOI: 10.1007/s13272-023-00644-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 12/20/2022] [Accepted: 01/18/2023] [Indexed: 05/24/2023]
Abstract
The dispersion of aerosols originating from one source, the 'index' passenger, within the cabin of the aircraft Do728 is studied experimentally using an aerosol-exhaling thermal manikin and in Reynolds-averaged Navier-Stokes simulations (RANS). The overall aim of the present study is the experimental determination of the aerosol spreading for the state-of-the-art mixing ventilation (MV) and to evaluate the potential of alternative ventilation concepts for controlling the aerosol spreading in RANS. For MV, the experiments showed that the ratio of inhaled to exhaled aerosol particles drops below 0.06% (volume ratio) for distances larger than two seat rows from the source. However, within a single row, the observed ratio is higher. Further, the dispersion is much weaker for a standing than for a seated index passenger. High air exchange rates and a well-guided flow prevent a dispersion of the aerosols in high concentrations over larger distances. Additionally, the positive effect of a mask and an increased air flow rate, and especially their combination are shown. In the complementary conducted RANS, the advantages of floor-based cabin displacement ventilation (CDV) which is alternative ventilation concept to MV, regarding spreading lengths and the dwell time of the aerosols in the cabin were determined. The obtained results also underline the importance of the flow field for the aerosol dispersion. Further, additional unsteady RANS (URANS) simulations of the short-term process of the initial aerosol cloud formation highlighted that the momentum decay of the breathing and the evaporation processes take place within a few seconds only. Supplementary Information The online version contains supplementary material available at 10.1007/s13272-023-00644-3.
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Affiliation(s)
- D. Schmeling
- German Aerospace Center (DLR), Institute of Aerodynamics and Flow Technology, Bunsenstr. 10, 37073 Göttingen, Germany
| | - A. Shishkin
- German Aerospace Center (DLR), Institute of Aerodynamics and Flow Technology, Bunsenstr. 10, 37073 Göttingen, Germany
| | - D. Schiepel
- German Aerospace Center (DLR), Institute of Aerodynamics and Flow Technology, Bunsenstr. 10, 37073 Göttingen, Germany
| | - C. Wagner
- German Aerospace Center (DLR), Institute of Aerodynamics and Flow Technology, Bunsenstr. 10, 37073 Göttingen, Germany
- Institute of Thermodynamics and Fluid Mechanics, Technische Universität Ilmenau, Am Helmholtzring 1, 98683 Ilmenau, Germany
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11
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Nishandar SR, He Y, Princevac M, Edwards RD. Fate of Exhaled Droplets From Breathing and Coughing in Supermarket Checkouts and Passenger Cars. ENVIRONMENTAL HEALTH INSIGHTS 2023; 17:11786302221148274. [PMID: 36644342 PMCID: PMC9834932 DOI: 10.1177/11786302221148274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 12/12/2022] [Indexed: 06/17/2023]
Abstract
The global pandemic of COVID-19 has highlighted the importance of understanding the role that exhaled droplets play in virus transmission in community settings. Computational Fluid Dynamics (CFD) enables systematic examination of roles the exhaled droplets play in the spread of SARS-CoV-2 in indoor environments. This analysis uses published exhaled droplet size distributions combined with terminal aerosol droplet size based on measured peak concentrations for SARS-CoV-2 RNA in aerosols to simulate exhaled droplet dispersion, evaporation, and deposition in a supermarket checkout area and rideshare car where close proximity with other individuals is common. Using air inlet velocity of 2 m/s in the passenger car and ASHRAE recommendations for ventilation and comfort in the supermarket, simulations demonstrate that exhaled droplets <20 μm that contain the majority of viral RNA evaporated leaving residual droplet nuclei that remain aerosolized in the air. Subsequently ~ 70% of these droplet nuclei deposited in the supermarket and the car with the reminder vented from the space. The maximum surface deposition of droplet nuclei/m2 for speaking and coughing were 2 and 819, 18 and 1387 for supermarket and car respectively. Approximately 15% of the total exhaled droplets (aerodynamic diameters 20-700 µm) were deposited on surfaces in close proximity to the individual. Due to the non-linear distribution of viral RNA across droplet sizes, however, these larger exhaled droplets that deposit on surfaces have low viral content. Maximum surface deposition of viral RNA was 70 and 1.7 × 103 virions/m2 for speaking and 2.3 × 104 and 9.3 × 104 virions/m2 for coughing in the supermarket and car respectively while the initial airborne concentration of viral RNA was 7 × 106 copies per ml. Integrating the droplet size distributions with viral load distributions, this study helps explain the apparent importance of inhalation exposures compared to surface contact observed in the pandemic.
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Affiliation(s)
- Sanika Ravindra Nishandar
- Department of Mechanical Engineering,
Bourns College of Engineering, University of California, Riverside, CA, USA
| | - Yucheng He
- Department of Mechanical Engineering,
Bourns College of Engineering, University of California, Riverside, CA, USA
| | - Marko Princevac
- Department of Mechanical Engineering,
Bourns College of Engineering, University of California, Riverside, CA, USA
| | - Rufus D Edwards
- Department of Epidemiology, Program in
Public Health, University of California Irvine, CA, USA
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12
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Shinohara N, Ogata M, Kim H, Kagi N, Tatsu K, Inui F, Naito W. Evaluation of shields and ventilation as a countermeasure to protect bus drivers from infection. ENVIRONMENTAL RESEARCH 2023; 216:114603. [PMID: 36279914 DOI: 10.1016/j.envres.2022.114603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 09/22/2022] [Accepted: 10/13/2022] [Indexed: 06/16/2023]
Abstract
We evaluated the deposition of droplets and droplet nuclei-generated by simulated coughing and talking from three points in a bus-on the driver's face and on surfaces around the driver (e.g., the steering wheel), based on whether countermeasures were taken, and assuming that an infected passenger was talking to the driver. When a shield, such as acrylic boards or polyvinyl chloride (PVC) sheets, was used as the countermeasure, the deposition of artificial droplets (>4 μm), emitted from beside or behind the driver, on his eyes, mouth, and cheeks reduced by two to three orders of magnitude or more. Deposition on the surfaces around the driver was also reduced following the use of shields. For artificial droplet nuclei (1.3 μm of polystyrene latex (PSL)) emitted from atomizers beside the driver, the operation of the ventilation fan (VF) and air conditioner (AC), and defroster (DEF) greatly reduced the driver's exposure, while the use of the shield did not. The infection risk of the driver was estimated through exposure to the virus via transfer to the mucosa via hands or surface-to-finger, direct adhesion on the mucosa, and direct inhalation of droplets and droplet nuclei. This is under the assumption that the droplets and droplet nuclei measured in this study are 40% the diameter of those after immediately leaving the mouth of the infected person and are constant regardless of particle size. When using the shield, total infection risk via droplet, airborne, and contact transmission was decreased by 75.0-99.8%. When the shield was not installed, the infection risk decreased by 9.74-48.7% with the operation of the VF, AC, and/or DEF.
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Affiliation(s)
- Naohide Shinohara
- National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba-shi, Ibaraki, 305-8569, Japan.
| | - Masayuki Ogata
- Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji-shi, Tokyo, 192-0397, Japan
| | - Hoon Kim
- National Institute of Public Health, 2-3-6 Minami, Wako-shi, Saitama, 351-0197, Japan
| | - Naoki Kagi
- Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8552, Japan
| | - Koichi Tatsu
- National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba-shi, Ibaraki, 305-8569, Japan; Isuzu Motors Ltd., 8 Tsuchidana, Fujisawa-shi, Kanagawa, 252-8501, Japan
| | - Fuminori Inui
- National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba-shi, Ibaraki, 305-8569, Japan
| | - Wataru Naito
- National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba-shi, Ibaraki, 305-8569, Japan
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13
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Nazari A, Hong J, Taghizadeh-Hesary F, Taghizadeh-Hesary F. Reducing Virus Transmission from Heating, Ventilation, and Air Conditioning Systems of Urban Subways. TOXICS 2022; 10:796. [PMID: 36548629 PMCID: PMC9784553 DOI: 10.3390/toxics10120796] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 12/13/2022] [Accepted: 12/15/2022] [Indexed: 06/17/2023]
Abstract
Aerosols carrying the virus inside enclosed spaces is an important mode of transmission for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), as supported by growing evidence. Urban subways are one of the most frequented enclosed spaces. The subway is a utilitarian and low-cost transit system in modern society. However, studies are yet to demonstrate patterns of viral transmission in subway heating, ventilation, and air conditioning (HVAC) systems. To fill this gap, we performed a computational investigation of the airflow (and associated aerosol transmission) in an urban subway cabin equipped with an HVAC system. We employed a transport equation for aerosol concentration, which was added to the basic buoyant solver to resolve the aerosol transmission inside the subway cabin. This was achieved by considering the thermal, turbulent, and induced ventilation flow effects. Using the probability of encountering aerosols on sampling surfaces crossing the passenger breathing zones, we detected the highest infection risk zones inside the urban subway under different settings. We proposed a novel HVAC system that can impede aerosol spread, both vertically and horizontally, inside the cabin. In the conventional model, the maximum probability of encountering aerosols from the breathing of infected individuals near the fresh-air ducts was equal to 51.2%. This decreased to 3.5% in the proposed HVAC model. Overall, using the proposed HVAC system for urban subways led to a decrease in the mean value of the probability of encountering the aerosol by approximately 84% compared with that of the conventional system.
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Affiliation(s)
- Ata Nazari
- Department of Mechanical Engineering, University of Tabriz, Tabriz 51666-16471, Iran
| | - Jiarong Hong
- Mechanical Engineering & Saint Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN 55455, USA
| | - Farzad Taghizadeh-Hesary
- ENT and Head and Neck Research Center and Department, The Five Sense Health Institute, School of Medicine, Iran University of Medical Sciences, Tehran 14535, Iran
| | - Farhad Taghizadeh-Hesary
- TOKAI Research Institute for Environment and Sustainability (TRIES), Tokai University, Hiratsuka-shi 259-1292, Kanagawa-ken, Japan
- School of Global Studies, Tokai University, Hiratsuka-shi 259-1292, Kanagawa-ken, Japan
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14
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Sun X, Wandelt S, Zhang A. COVID-19 pandemic and air transportation: Summary of Recent Research, Policy Consideration and Future Research Directions. TRANSPORTATION RESEARCH INTERDISCIPLINARY PERSPECTIVES 2022; 16:100718. [PMID: 36407295 PMCID: PMC9640395 DOI: 10.1016/j.trip.2022.100718] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 11/02/2022] [Accepted: 11/06/2022] [Indexed: 05/19/2023]
Abstract
The COVID-19 pandemic can be considered an unparalleled disruption to the aviation industry in the last century. Starting with an at-that-time inconceivable reduction in the number of flights from March 2020 to May 2020, the aviation industry has been trying to navigate through and out of the crisis. This process is accompanied with a significant number of scientific studies, reporting on the direct and indirect impact of the COVID-19 pandemic on aviation and vice versa. This paper reviews the impacts in context of the recent literature. We have collected nearly 200 well-published papers on the subject in the years 2021/2022 and dissected them into a framework of eight categories, built around: airlines, airports, passengers, workforce, markets, contagion, sustainability, and economics. We highlight the essence of findings in the literature and derive a set of future research directions and policy considerations which we deem important on the way towards pandemic-resilient aviation.
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Affiliation(s)
- Xiaoqian Sun
- National Key Laboratory of CNS/ATM, School of Electronic and Information Engineering, Beihang University, 100191 Beijing, China
| | - Sebastian Wandelt
- National Key Laboratory of CNS/ATM, School of Electronic and Information Engineering, Beihang University, 100191 Beijing, China
| | - Anming Zhang
- Sauder School of Business, University of British Columbia, Vancouver, BC, Canada
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15
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Takii A, Yamakawa M, Kitagawa A, Watamura T, Chung YM, Kim M. Numerical model for cough-generated droplet dispersion on moving escalator with multiple passengers. INDOOR AIR 2022; 32:e13131. [PMID: 36437661 PMCID: PMC9827918 DOI: 10.1111/ina.13131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 09/15/2022] [Accepted: 09/23/2022] [Indexed: 06/16/2023]
Abstract
To investigate the motion of virus-laden droplets between moving passengers in line, we performed numerical simulations of the distribution of airborne droplets within a geometrically detailed model similar to an actual escalator. The left and right sides and the ceiling of the escalator model were surrounded by walls, assuming a subway used by many people every day with concern to virus-laden droplets. Steps and handrails were incorporated in the model to faithfully compute the escalator-specific flow field. The ascending and descending movements of the escalator were performed with 10 or 5 passengers standing at different boarding intervals. To resolve the unsteady airflow that is excited by a moving boundary consisting of passengers, steps, and handrails, the moving computational domain method based on the moving-grid finite-volume method was applied. On the basis of the consideration that the droplets were small enough, droplet dispersion was computed by solving the equation of virus-laden droplet motion using a pre-computed velocity field, in which the flow rate of a cough, diameter distribution, and evaporation of droplets are incorporated. The simulation resolved the detailed motion of droplets in flow, and therefore, we were able to evaluate the risk of viral adhesion to following passengers. As a result, we found that the ascending escalator had a higher risk of being exposed to virus-laden droplets than the descending escalator. We also reported that the chance of viral droplet adhesion decreases as the distance from the infected person increases, emphasizing the importance of social distancing.
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Affiliation(s)
- Ayato Takii
- Department of Mechanical EngineeringKyoto Institute of TechnologyKyotoJapan
| | - Masashi Yamakawa
- Department of Mechanical EngineeringKyoto Institute of TechnologyKyotoJapan
| | - Atsuhide Kitagawa
- Department of Mechanical EngineeringKyoto Institute of TechnologyKyotoJapan
| | - Tomoaki Watamura
- Department of Mechanical EngineeringKyoto Institute of TechnologyKyotoJapan
| | | | - Minsuok Kim
- School of Mechanical, Electrical and Manufacturing EngineeringLoughborough UniversityLoughboroughUK
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16
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Multi-objective performance assessment of HVAC systems and physical barriers on COVID-19 infection transmission in a high-speed train. JOURNAL OF BUILDING ENGINEERING 2022; 53:104544. [PMCID: PMC9022448 DOI: 10.1016/j.jobe.2022.104544] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Revised: 04/11/2022] [Accepted: 04/17/2022] [Indexed: 06/16/2023]
Abstract
A computational fluid dynamics (CFD) simulation was performed to model and study the transmission risk associated with cough-related SARS-CoV-2 droplets in a real-world high-speed train (HST). In this study, the evaporating of the droplets was considered. Simulation data were post-processed to assess the fraction of the particles deposited on each passenger's face and body, suspended in air, and escaped from exhausts. Firstly, the effects of temperature, relative humidity, ventilation rate, injection source, exhausts' location and capacity, and adding the physical barriers on evaporation and transport of respiratory droplets are investigated in long distance HST. The results demonstrate that overall, 6–43% of the particles were suspended in the cabin after 2.7 min, depending on conditions, and 3–58% of the particles were removed from the cabin in the same duration. Use of physical barriers and high ventilation rate is therefore recommended for both personal and social protection. We found more exhaust capacity and medium relative humidity to be effective in reducing the particles' transmission potential across all studied scenarios. The results indicate that reducing ventilation rate and exhaust capacity, increased aerosols shelf time and dispersion throughout the cabin.
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17
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Wang Q, Gu J, An T. The emission and dynamics of droplets from human expiratory activities and COVID-19 transmission in public transport system: A review. BUILDING AND ENVIRONMENT 2022; 219:109224. [PMID: 35645454 PMCID: PMC9126829 DOI: 10.1016/j.buildenv.2022.109224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Revised: 05/03/2022] [Accepted: 05/20/2022] [Indexed: 06/15/2023]
Abstract
The public transport system, containing a large number of passengers in enclosed and confined spaces, provides suitable conditions for the spread of respiratory diseases. Understanding how diseases are transmitted in public transport environment is of vital importance to public health. However, this is a highly multidisciplinary matter and the related physical processes including the emissions of respiratory droplets, the droplet dynamics and transport pathways, and subsequently, the infection risk in public transport, are poorly understood. To better grasp the complex processes involved, a synthesis of current knowledge is required. Therefore, we conducted a review on the behaviors of respiratory droplets in public transport system, covering a wide scope from the emission profiles of expiratory droplets, the droplet dynamics and transport, to the transmission of COVID-19 in public transport. The literature was searched using related keywords in Web of Science and PubMed and screened for suitability. The droplet size is a key parameter in determining the deposition and evaporation, which together with the exhaled air velocity largely determines the horizontal travel distance. The potential transmission route and transmission rate in public transport as well as the factors influencing the virus-laden droplet behaviors and virus viability (such as ventilation system, wearing personal protective equipment, air temperature and relative humidity) were also discussed. The review also suggests that future studies should address the uncertainties in droplet emission profiles associated with the measurement techniques, and preferably build a database based on a unified testing protocol. Further investigations based on field measurements and modeling studies into the influence of different ventilation systems on the transmission rate in public transport are also needed, which would provide scientific basis for controlling the transmission of diseases.
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Affiliation(s)
- Qiaoqiao Wang
- Institute for Environmental and Climate Research, Jinan University, 511443, Guangzhou, China
- Guangdong-Hong Kong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, 511443, Guangzhou, China
| | - Jianwei Gu
- Guangdong-Hong Kong-Macao Joint Laboratory for Contaminants Exposure and Health, Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, 510006, Guangzhou, China
- Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, Guangdong Technology Research Center for Photocatalytic Technology Integration and Equipment Engineering, School of Environmental Science and Engineering, Guangdong University of Technology, 510006, Guangzhou, China
| | - Taicheng An
- Guangdong-Hong Kong-Macao Joint Laboratory for Contaminants Exposure and Health, Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, 510006, Guangzhou, China
- Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, Guangdong Technology Research Center for Photocatalytic Technology Integration and Equipment Engineering, School of Environmental Science and Engineering, Guangdong University of Technology, 510006, Guangzhou, China
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18
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van Beest MRRS, Arpino F, Hlinka O, Sauret E, van Beest NRTP, Humphries RS, Buonanno G, Morawska L, Governatori G, Motta N. Influence of indoor airflow on particle spread of a single breath and cough in enclosures: Does opening a window really 'help'? ATMOSPHERIC POLLUTION RESEARCH 2022; 13:101473. [PMID: 35692900 PMCID: PMC9167821 DOI: 10.1016/j.apr.2022.101473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 05/27/2022] [Accepted: 05/29/2022] [Indexed: 06/15/2023]
Abstract
The spread of respiratory diseases via aerosol particles in indoor settings is of significant concern. The SARS-CoV-2 virus has been found to spread widely in confined enclosures like hotels, hospitals, cruise ships, prisons, and churches. Particles exhaled from a person indoors can remain suspended long enough for increasing the opportunity for particles to spread spatially. Careful consideration of the ventilation system is essential to minimise the spread of particles containing infectious pathogens. Previous studies have shown that indoor airflow induced by opened windows would minimise the spread of particles. However, how outdoor airflow through an open window influences the indoor airflow has not been considered. The aim of this study is to provide a clear understanding of the indoor particle spread across multiple rooms, in a situation similar to what is found in quarantine hotels and cruise ships, using a combination of HVAC (Heating, Ventilation and Air-Conditioning) ventilation and an opening window. Using a previously validated mathematical model, we used 3D CFD (computational fluid dynamics) simulations to investigate to what extent different indoor airflow scenarios contribute to the transport of a single injection of particles ( 1 . 3 μ m ) in a basic 3D multi-room indoor environment. Although this study is limited to short times, we demonstrate that in certain conditions approximately 80% of the particles move from one room to the corridor and over 60% move to the nearby room within 5 to 15 s. Our results provide additional information to help identifying relevant recommendations to limit particles from spreading in enclosures.
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Affiliation(s)
- M R R S van Beest
- School of Chemistry and Physics, Queensland University of Technology, Brisbane, Australia
- Software Systems Group, CSIRO | DATA61, Brisbane, Queensland, Australia
| | - F Arpino
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, Italy
| | - O Hlinka
- Information Management & Technology (IM&T), CSIRO, Pullenvale, Queensland, Australia
| | - E Sauret
- School of Mechanical, Medical and Process Engineering, Queensland University of Technology, Brisbane, Australia
| | - N R T P van Beest
- Software Systems Group, CSIRO | DATA61, Brisbane, Queensland, Australia
| | - R S Humphries
- Climate Science Centre, CSIRO Oceans and Atmosphere, Aspendale, Victoria, Australia
| | - G Buonanno
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, Italy
| | - L Morawska
- School of Earth and Atmospheric Sciences, Queensland University of Technology, Brisbane, Australia
| | - G Governatori
- Software Systems Group, CSIRO | DATA61, Brisbane, Queensland, Australia
| | - N Motta
- School of Chemistry and Physics, Queensland University of Technology, Brisbane, Australia
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19
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Stiehl B, Shrestha R, Schroeder S, Delgado J, Bazzi A, Reyes J, Kinzel M, Ahmed K. The effect of relative air humidity on the evaporation timescales of a human sneeze. AIP ADVANCES 2022; 12:075210. [PMID: 35989720 PMCID: PMC9386616 DOI: 10.1063/5.0102078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 06/08/2022] [Indexed: 06/15/2023]
Abstract
The present paper investigates droplet and aerosol emission from the human respiratory function by numerical and experimental methods, which is analyzed at the worst-case scenario, a violent sneeze without a face covering. The research findings develop the understanding of airborne disease transmission relevant to COVID-19, its recent variants, and other airborne pathogens. A human sneeze is studied using a multiphase Computational Fluid Dynamics (CFD) model using detached eddy simulation coupled to the emission of droplets that break up, evaporate, and disperse. The model provides one of the first experimental benchmarks of CFD predictions of a human sneeze event. The experiments optically capture aerosols and droplets and are processed to provide spatiotemporal data to validate the CFD model. Under the context of large random uncertainty, the studies indicate the reasonable correlation of CFD prediction with experimental measurements using velocity profiles and exposure levels, indicating that the model captures the salient details relevant to pathogen dispersion. Second, the CFD model was extended to study the effect of relative humidity with respect to the Wells curve, providing additional insight into the complexities of evaporation and sedimentation characteristics in the context of turbulent and elevated humidity conditions associated with the sneeze. The CFD results indicated correlation with the Wells curve with additional insight into features, leading to non-conservative aspects associated with increased suspension time. These factors are found to be associated with the combination of evaporation and fluid-structure-induced suspension. This effect is studied for various ambient air humidity levels and peaks for lower humidity levels, indicating that the Wells curve may need a buffer in dry climates. Specifically, we find that the increased risk in dry climates may be up to 50% higher than would be predicted using the underlying assumptions in Wells' model.
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Affiliation(s)
| | | | | | | | | | | | | | - Kareem Ahmed
- Author to whom correspondence should be addressed: . Tel.: (407) 823-5710
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20
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Numerical Investigation on the Droplet Dispersion inside a Bus and the Infection Risk Prediction. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12125909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
COVID-19 can be easily transmitted to passengers by inhaling exhaled droplets from the infected person in a bus. Therefore, studying droplet dispersion would provide further insight into the mechanism of virus transmission and predict the risk of infection among passengers on a bus. In this research, a bus equipped with air-conditioning was employed as the research object. To determine the dispersion path, concentration distribution, and escape time of the droplets, computational fluid dynamic (CFD) was applied to simulate the flow field and the droplets’ dispersion. The effect of the air supply rate, the location of vents, and the location of infected persons on the dispersion were discussed. Based on the distribution of droplets in the cabin calculated by CFD, a superposition method was used to determine the number of virus particles inhaled by every individual passenger over a four-hour journey. Then, infection risk was assessed by the Wells-Riley equation for all the passengers in the cabin after the whole journey. The results show that the distribution of droplets in the cabin is greatly influenced by the location of the infected person, and the airflow pattern is highly associated with the air supply rate and the location of vents. The infection risk of passengers located at the droplet dispersion path and the distance from the infected persons less than 2.2 m is over 10%. The increase in the air supply rate could speed up the spread of the droplets but at the same time, it could reduce the infection risk.
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21
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Droplets Transmission Mechanism in a Commercial Wide-Body Aircraft Cabin. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12104889] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
COVID-19 is a respiratory infectious disease that spreads readily between people, and an urgent issue of passengers’ exposure risk assessment in commercial aircraft has been raised because an aircraft cabin as a confined space may carry and transmit the disease worldwide. In this study, the droplets transmission process under different ventilation systems in a twin-aisle wide-body aircraft was studied using CFD simulations and the infection risk of passengers was assessed by the improved Wells–Riley model. Numerical results found that the transmission mechanism of droplets in the aircraft cabin was different depending on the type of ventilation systems and the location of the infectious source. Annular airflow could effectively enhance the ability of droplets transmission, while direct airflow, represented by displacement ventilation, could significantly inhibit droplets transmission. Accordingly, a new type of ventilation system was proposed based on the concept that the overall space is organized by annular airflow and the local area is direct airflow. Compared with sidewall mixing ventilation system, the infection risk of the new ventilation system presented in this study is reduced by 27%.
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22
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Shinohara N, Tatsu K, Kagi N, Kim H, Sakaguchi J, Ogura I, Murashima Y, Sakurai H, Naito W. Air exchange rates and advection-diffusion of CO 2 and aerosols in a route bus for evaluation of infection risk. INDOOR AIR 2022; 32:e13019. [PMID: 35347782 PMCID: PMC9111735 DOI: 10.1111/ina.13019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 01/30/2022] [Accepted: 03/03/2022] [Indexed: 06/14/2023]
Abstract
As COVID-19 continues to spread, infection risk on public transport is concerning. Air exchange rates (ACH) and advection-diffusion of CO2 and particles were determined in a route bus to evaluate the infection risk. ACH increased with bus speed whether windows were open or closed, and ACH were greater when more windows were open. With two open windows, ACH was greater when a front and rear window were open than when two rear windows were open. With both front and rear ventilation fans set to exhaust, ACH was more than double that when both were set to supply. With air conditioning (AC) off, CO2 and particles spread proportionally at the same rate from a source, whereas with the AC on, the spread rate of particles was about half that of CO2 , because particles might be trapped by a prefilter on the AC unit. Infection risk can be reduced by equipping AC unit with an appropriate filter. Calculations with a modified Wells-Riley equation showed that average infection risk was reduced by 92% in the moving bus with windows open comparing to with windows closed. When the bus was moving with windows closed, exhaust fan operation reduced the average risk by 35%.
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Affiliation(s)
- Naohide Shinohara
- National Institute of Advanced Industrial Science and Technology (AIST)TsukubaIbarakiJapan
| | | | - Naoki Kagi
- Tokyo Institute of TechnologyMeguro‐ku, TokyoJapan
| | - Hoon Kim
- National Institute of Public HealthWakoSaitamaJapan
| | - Jun Sakaguchi
- University of Niigata PrefectureNiigata‐City, NiigartaJapan
| | - Isamu Ogura
- National Institute of Advanced Industrial Science and Technology (AIST)TsukubaIbarakiJapan
| | - Yoshiko Murashima
- National Institute of Advanced Industrial Science and Technology (AIST)TsukubaIbarakiJapan
| | - Hiromu Sakurai
- National Institute of Advanced Industrial Science and Technology (AIST)TsukubaIbarakiJapan
| | - Wataru Naito
- National Institute of Advanced Industrial Science and Technology (AIST)TsukubaIbarakiJapan
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23
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Haq MF, Cadnum JL, Carlisle M, Hecker MT, Donskey CJ. SARS in Cars: Carbon Dioxide Levels Provide a Simple Means to Assess Ventilation in Motor Vehicles. Pathog Immun 2022; 7:19-30. [PMID: 35178491 PMCID: PMC8843085 DOI: 10.20411/pai.v7i1.493] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2021] [Accepted: 01/14/2022] [Indexed: 11/25/2022] Open
Abstract
Background: Poorly ventilated enclosed spaces pose a risk for airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other respiratory viruses. Limited information is available on ventilation in motor vehicles under differing driving conditions. Methods: We conducted carbon dioxide measurements to assess ventilation in motor vehicles under varying driving conditions with 2 to 3 vehicle occupants. During routine driving, carbon dioxide produced by the breathing of vehicle occupants was measured inside 5 cars and a van under a variety of driving conditions with or without the ventilation fan on and with windows open or closed. Carbon dioxide readings above 800 parts per million (ppm) were considered an indicator of suboptimal ventilation. Results: Carbon dioxide levels remained below 800 ppm in all vehicles if the ventilation fan was on and/or the windows were open while parked or during city or highway driving. With the ventilation system set on non-recirculation mode, carbon dioxide levels rose above 800 ppm in all vehicles when the fan was off and the windows were closed while parked and during city driving, and in 2 of the 6 vehicles during highway driving. With the ventilation system set on recirculation mode, carbon dioxide rose above 800 ppm within 10 minutes in all vehicles tested. Conclusion: Carbon dioxide measurements could provide a practical and rapid method to assess ventilation in motor vehicles. Simple measures such as opening windows, turning on the fan, and avoiding the recirculation mode greatly improve ventilation.
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Affiliation(s)
- Muhammed F. Haq
- Research Service, Louis Stokes Cleveland VA Medical Center, Cleveland, Ohio
| | - Jennifer L. Cadnum
- Research Service, Louis Stokes Cleveland VA Medical Center, Cleveland, Ohio
| | - Matthew Carlisle
- Research Service, Louis Stokes Cleveland VA Medical Center, Cleveland, Ohio
| | - Michelle T. Hecker
- Department of Infectious Diseases, MetroHealth Medical Center, Cleveland, Ohio
- Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Curtis J. Donskey
- Case Western Reserve University School of Medicine, Cleveland, Ohio
- Research, Education, and Clinical Center, Louis Stokes Cleveland VA Medical Center, Cleveland, Ohio
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24
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Mathai V, Das A, Breuer K. Aerosol transmission in passenger car cabins: Effects of ventilation configuration and driving speed. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2022; 34:021904. [PMID: 35342278 PMCID: PMC8939464 DOI: 10.1063/5.0079555] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Accepted: 01/15/2022] [Indexed: 05/25/2023]
Abstract
Identifying the potential routes of airborne transmission during transportation is of critical importance to limit the spread of the SARS-CoV-2 virus. Here, we numerically solve the Reynolds-averaged Navier-Stokes equations along with the transport equation for a passive scalar in order to study aerosol transmission inside the passenger cabin of an automobile. Extending the previous work on this topic, we explore several driving scenarios including the effects of having the windows fully open, half-open, and one-quarter open, the effect of opening a moon roof, and the scaling of the aerosol transport as a function of vehicle speed. The flow in the passenger cabin is largely driven by the external surface pressure distribution on the vehicle, and the relative concentration of aerosols in the cabin scales inversely with vehicle speed. For the simplified geometry studied here, we find that the half-open windows configuration has almost the same ventilation effectively as the one with the windows fully open. The utility of the moonroof as an effective exit vent for removing the aerosols generated within the cabin space is discussed. Using our results, we propose a "speed-time" map, which gives guidance regarding the relative risk of transmission between driver and passenger as a function of trip duration and vehicle speed. A few strategies for the removal of airborne contaminants during low-speed driving, or in a situation where the vehicle is stuck in traffic, are suggested.
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Affiliation(s)
- Varghese Mathai
- Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, USA
| | - Asimanshu Das
- Center for Fluid Mechanics, Brown University, Providence, Rhode Island 02912, USA
| | - Kenneth Breuer
- Center for Fluid Mechanics, Brown University, Providence, Rhode Island 02912, USA
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25
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Liu M, Liu J, Cao Q, Li X, Liu S, Ji S, Lin CH, Wei D, Shen X, Long Z, Chen Q. Evaluation of different air distribution systems in a commercial airliner cabin in terms of comfort and COVID-19 infection risk. BUILDING AND ENVIRONMENT 2022; 208:108590. [PMID: 34812218 PMCID: PMC8599143 DOI: 10.1016/j.buildenv.2021.108590] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 10/09/2021] [Accepted: 11/15/2021] [Indexed: 05/24/2023]
Abstract
The air distribution system in an airliner plays a key role in maintaining a comfortable and healthy environment in the aircraft cabin. To evaluate the performance of a novel displacement ventilation (DV) system and a traditional mixing ventilation (MV) system in an airliner cabin, this study conducted experiments and simulations in a seven-row cabin mockup. This investigation used ultrasonic anemometers and T-thermocouples to measure the air velocity, temperature and distribution of 1 μm and 5 μm particles. Simulation verifications were performed for these operating conditions, and additional scenarios with different occurrence source locations were also simulated. This study combined the Wells-Riley equation with a real case based on a COVID-19 outbreak among passengers on a long-distance bus to obtain the COVID-19 quanta value. Through an evaluation of the airflow organization, thermal comfort, and risk of COVID-19 infection, the two ventilation systems were compared. This investigation found that polydisperse particles should be used to calculate the risk of infection in airliner cabins. In addition, at the beginning of the pandemic, the infection risk with DV was lower than that with MV. In the middle and late stages of the epidemic, the infection risk with MV can be reduced when passengers wear masks, leading to an infection risk approximately equal to that of DV.
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Affiliation(s)
- Mingxin Liu
- Tianjin Key Lab of Indoor Air Environmental Quality Control, School of Environmental Science and Engineering, Tianjin University, Tianjin, 300072, China
| | - Junjie Liu
- Tianjin Key Lab of Indoor Air Environmental Quality Control, School of Environmental Science and Engineering, Tianjin University, Tianjin, 300072, China
| | - Qing Cao
- School of Civil Engineering, Dalian University of Technology (DUT), 2 Linggong Road, Dalian, 116024, China
- Dalian University of Technology, Dalian, China
| | - Xingyang Li
- Tianjin Key Lab of Indoor Air Environmental Quality Control, School of Environmental Science and Engineering, Tianjin University, Tianjin, 300072, China
| | - Sumei Liu
- Tianjin Key Lab of Indoor Air Environmental Quality Control, School of Environmental Science and Engineering, Tianjin University, Tianjin, 300072, China
| | - Shengcheng Ji
- Beijing Aeronautical Science & Technology Research Institute of COMAC, Beijing, China
| | - Chao-Hsin Lin
- Environmental Control Systems, Boeing Commercial Airplanes, Everett, WA, 98203, USA
| | - Daniel Wei
- Boeing Research & Technology, Beijing, 100027, China
| | - Xiong Shen
- Tianjin Key Lab of Indoor Air Environmental Quality Control, School of Environmental Science and Engineering, Tianjin University, Tianjin, 300072, China
| | - Zhengwei Long
- Tianjin Key Lab of Indoor Air Environmental Quality Control, School of Environmental Science and Engineering, Tianjin University, Tianjin, 300072, China
| | - Qingyan Chen
- Department of Building Environment and Energy Engineering, The Hong Kong Polytechnic University, Hong Kong
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26
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Biswas R, Pal A, Pal R, Sarkar S, Mukhopadhyay A. Risk assessment of COVID infection by respiratory droplets from cough for various ventilation scenarios inside an elevator: An OpenFOAM-based computational fluid dynamics analysis. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2022; 34:013318. [PMID: 35340680 PMCID: PMC8939552 DOI: 10.1063/5.0073694] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2021] [Accepted: 12/30/2021] [Indexed: 05/15/2023]
Abstract
Respiratory droplets-which may contain disease spreading virus-exhaled during speaking, coughing, or sneezing are one of the significant causes for the spread of the ongoing COVID-19 pandemic. The droplet dispersion depends on the surrounding air velocity, ambient temperature, and relative humidity. In a confined space like an elevator, the risk of transmission becomes higher when there is an infected person inside the elevator with other individuals. In this work, a numerical investigation is carried out in a three-dimensional domain resembling an elevator using OpenFoam. Three different modes of air ventilation, viz., quiescent, axial exhaust draft, and exhaust fan, have been considered to investigate the effect of ventilation on droplet transmission for two different climatic conditions (30 °C , 50% relative humidity and 10 °C , 90% relative humidity). The risk assessment is quantified using a risk factor based on the time-averaged droplet count present near the passenger's hand to head region (risky height zone). The risk factor drops from 40% in a quiescent scenario to 0% in an exhaust fan ventilation condition in a hot dry environment. In general, cold humid conditions are safer than hot dry conditions as the droplets settle down quickly below the risky height zone owing to their larger masses maintained by negligible evaporation. However, an exhaust fan renders the domain in a hot dry ambience completely safe (risk factor, 0%) in 5.5 s whereas it takes 7.48 s for a cold humid ambience.
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Affiliation(s)
- Riddhideep Biswas
- Department of Mechanical Engineering, Jadavpur University, Kolkata-700032, India
| | - Anish Pal
- Department of Mechanical Engineering, Jadavpur University, Kolkata-700032, India
| | - Ritam Pal
- Department of Mechanical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Sourav Sarkar
- Department of Mechanical Engineering, Jadavpur University, Kolkata-700032, India
- Author to whom correspondence should be addressed:
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Wang H, Li Z, Liu Y, Zhu L, Zhou Z. Experimental study of the dispersion of cough-generated droplets from a person going up- or downstairs. AIP ADVANCES 2022; 12:015002. [PMID: 35003882 PMCID: PMC8734944 DOI: 10.1063/5.0073880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 11/22/2021] [Indexed: 06/14/2023]
Abstract
The dispersion of cough-generated droplets from a person going up- or downstairs was investigated through a laboratory experiment in a water tunnel. This experiment was carried out with a manikin mounted at inclination angles facing the incoming flow to mimic a person going up or down. Detailed velocity measurements and flow visualization were conducted in the water tunnel experiments. To investigate the influence of the initial position on the motion of particles, a virtual particle approach was adopted to simulate the dispersion of particles using the measured velocity field. Particle clustering, which is caused by the unsteadiness of the flow, was observed in both flow visualization and virtual particle simulation. For the case of going upstairs, particles are concentrated below the person's shoulder and move downward with a short travel distance. For the case of going downstairs, particles dispersing over the person's head advect over for a long distance. We also found that the motion of the particles is closely related to the initial position. According to the results in this study, suggestions for the prevention of respiratory infectious disease are made.
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Yang Y, Wang Y, Tian L, Su C, Chen Z, Huang Y. Effects of purifiers on the airborne transmission of droplets inside a bus. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2022; 34:017108. [PMID: 35340683 PMCID: PMC8939553 DOI: 10.1063/5.0081230] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 12/28/2021] [Indexed: 05/25/2023]
Abstract
During an airborne infectious disease outbreak, bus passengers can be easily infected by the dispersion of exhaled droplets from an infected passenger. Therefore, measures to control the transport of droplets are necessary, such as a mask or purifier. The current research examined aerosol transport in a bus with air-conditioning. To determine the dispersion path, deposition distribution, and droplet escape time, the computational fluid dynamics were used to predict the flow field and the dispersion of droplets considering the effects of droplet size, location of the infected person, and purifier type. In addition, based on the viability and the number of virus particles in a droplet, the total number of virus particles inhaled by passengers over a 4-h journey was obtained by the superposition method. The Wells-Riley equation was then used to assess the infection risk of the passengers in the bus cabin. The results showed that droplets with a size of 1-20 μm have essentially the same deposition characteristics, and the location of the infected passenger affects the distribution of droplets' transport and the effectiveness of a purifier in removing droplets. A purifier can effectively remove droplets from passengers' coughs and reduce the infection risk of passengers. The performance of the smaller purifiers is not as stable as that of the larger purifiers, and the performance is influenced by the airflow structure where the infected passenger is located.
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Affiliation(s)
| | | | - Linli Tian
- Author to whom correspondence should be addressed:. Tel.: 0086-13317136217
| | | | - Zhixin Chen
- Hubei Key Laboratory of Advanced Technology for Automotive Components, Wuhan University of Technology, Wuhan, Hubei 430070, China
| | - Yuanyi Huang
- SAIC GM Wuling Automobile Co., Ltd, Liuzhou, Guangxi 545000, China
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29
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Wang W, Wang F, Lai D, Chen Q. Evaluation of SARS-COV-2 transmission and infection in airliner cabins. INDOOR AIR 2022; 32:e12979. [PMID: 35048429 DOI: 10.1111/ina.12979] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 11/30/2021] [Accepted: 12/15/2021] [Indexed: 06/14/2023]
Abstract
Commercial airliners have played an important role in spreading the SARS-CoV-2 virus worldwide. This study used computational fluid dynamics (CFD) to simulate the transmission of SARS-CoV-2 on a flight from London to Hanoi and another from Singapore to Hangzhou. The dispersion of droplets of different sizes generated by coughing, talking, and breathing activities in a cabin by an infected person was simulated by means of the Lagrangian method. The SARS-CoV-2 virus contained in expiratory droplets traveled with the cabin air distribution and was inhaled by other passengers. Infection was determined by counting the number of viral copies inhaled by each passenger. According to the results, our method correctly predicted 84% of the infected/uninfected cases on the first flight. The results also show that wearing masks and reducing conversation frequency between passengers could help to reduce the risk of exposure on the second flight.
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Affiliation(s)
- Wensi Wang
- Tianjin Key Laboratory of Indoor Air Environmental Quality Control, School of Environmental Science and Engineering, Tianjin University, Tianjin, China
| | - Feng Wang
- Tianjin Key Laboratory of Indoor Air Environmental Quality Control, School of Environmental Science and Engineering, Tianjin University, Tianjin, China
| | - Dayi Lai
- Department of Architecture, Shanghai Jiao Tong University, Shanghai, China
| | - Qingyan Chen
- Department of Building Environment and Energy Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong
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30
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Zhang J, Qin F, Qin X, Li J, Tian S, Lou J, Kang X, Lian H, Niu S, Zhang W, Chen Y. Transmission of SARS-CoV-2 during air travel: a descriptive and modelling study. Ann Med 2021; 53:1569-1575. [PMID: 34463165 PMCID: PMC8409939 DOI: 10.1080/07853890.2021.1973084] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 08/21/2021] [Indexed: 12/21/2022] Open
Abstract
OBJECTIVES To explore the potential of SARS-CoV-2 spread during air travel and the risk of in-flight transmission. METHODS We enrolled all passengers and crew suspected of being infected with SARS-CoV-2, who bounded for Beijing on international flights. We specified the characteristics of all confirmed cases of COVID-19 infection and utilised Wells-Riley equation to estimate the infectivity of COVID-19 during air travel. RESULTS We screened 4492 passengers and crew with suspected COVID-19 infection, verified 161 confirmed cases (mean age 28.6 years), and traced two confirmed cases who may have been infected in the aircraft. The estimated infectivity was 375 quanta/h (range 274-476), while the effective infectivity was only 4 quanta/h (range 2-5). The risk of per-person infection during a 13 h air travel in economy class was 0.56‰ (95% CI 0.41‰-0.72‰). CONCLUSION We found that the universal use of face masks on the flight, together with the plane's ventilation system, significantly decreased the infectivity of COVID-19.KEY MESSAGESThe COVID-19 pandemic is changing the lifestyle in the world, especially air travel which has the potential to spread SARS-CoV-2.The universal use of face masks on the flight, together with the plane's ventilation system, significantly decreased the infectivity of COVID-19 on an aircraft.Our findings suggest that the risk of infection in aircraft was negligible.
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Affiliation(s)
- Jinjun Zhang
- Beijing Emergency Medical Center, Beijing, China
| | - Fei Qin
- School of Electronic Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing, China
| | - Xinyan Qin
- Uninted Family Healthcare, Beijing, China
| | - Jianren Li
- Beijing Emergency Medical Center, Beijing, China
| | - Sijia Tian
- Beijing Emergency Medical Center, Beijing, China
| | - Jing Lou
- Beijing Emergency Medical Center, Beijing, China
| | - Xuqin Kang
- Beijing Emergency Medical Center, Beijing, China
| | - Huixin Lian
- Beijing Emergency Medical Center, Beijing, China
| | - Shengmei Niu
- Beijing Emergency Medical Center, Beijing, China
| | | | - Yuguo Chen
- Emergency Department, Qilu Hospital, Shandong University, Jinan, China
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31
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Peña-Monferrer C, Antao S, Manson-Sawko R. Numerical investigation of droplets in a cross-ventilated space with sitting passengers under asymptomatic virus transmission conditions. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:123314. [PMID: 35002204 PMCID: PMC8728630 DOI: 10.1063/5.0070625] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Accepted: 11/05/2021] [Indexed: 06/14/2023]
Abstract
Asymptomatic virus transmission in public transportation is a complex process that is difficult to analyze computationally and experimentally. We present a high-resolution computational study for investigating droplet dynamics under a speech-like exhalation mode. A large eddy simulation coupled with Lagrangian tracking of drops was used to model a rectangular space with sitting thermal bodies and cross-ventilated with a multislot diffuser. Release of drops from different seat positions was evaluated to analyze the decontamination performance of the ventilation system. The results showed an overall good performance, with an average of 24.1% of droplets removed through the exhaust in the first 40 s. The droplets' distribution revealed that higher concentrations were less prevalent along the center of the domain where the passengers sit. Longitudinal contamination between rows was noted, which is a negative aspect for containing the risk of infection in a given row but has the benefit of diluting the concentration of infectious droplets. Droplets from the window seat raised more vertically and invaded the space of other passengers to a lesser extent. In contrast, droplets released from the middle seat contaminated more the aisle passenger's space, indicating that downward flow from personal ventilation could move down droplets to its breathing region. Droplets released from the aisle were dragged down by the ventilation system immediately. The distance of drops to the mouth of the passengers showed that the majority passed at a relatively safe distance. However, a few of them passed at a close distance of the order of magnitude of 1 cm.
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Affiliation(s)
- C Peña-Monferrer
- IBM Research Europe, The Hartree Centre, Warrington WA4 4AD, United Kingdom
| | - S Antao
- IBM Research Europe, The Hartree Centre, Warrington WA4 4AD, United Kingdom
| | - R Manson-Sawko
- IBM Research Europe, The Hartree Centre, Warrington WA4 4AD, United Kingdom
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32
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Kumar B, Chatterjee S, Agrawal A, Bhardwaj R. Evaluating a transparent coating on a face shield for repelling airborne respiratory droplets. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:111705. [PMID: 34803361 PMCID: PMC8597715 DOI: 10.1063/5.0073724] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2021] [Accepted: 10/26/2021] [Indexed: 05/05/2023]
Abstract
A face shield is an important personal protective equipment to avoid the airborne transmission of COVID-19. We assess a transparent coating on a face shield that repels airborne respiratory droplets to mitigate the spread of COVID-19. The surface of the available face shield is hydrophilic and exhibits high contact angle hysteresis. The impacting droplets stick on it, resulting in an enhanced risk of fomite transmission of the disease. Further, it may get wetted in the rain, and moisture may condense on it in the presence of large humidity, which may blur the user's vision. Therefore, the present study aims to improve the effectiveness of a face shield. Our measurements demonstrate that the face shield, coated by silica nanoparticles solution, becomes superhydrophobic and results in a nominal hysteresis to the underlying surface. We employ high-speed visualization to record the impact dynamics of microliter droplets with a varying impact velocity and angle of attack on coated and non-coated surfaces. While the droplet on non-coated surface sticks to it, in the coated surface the droplets bounce off and roll down the surface, for a wide range of Weber number. We develop an analytical model and present a regime map of the bouncing and non-bouncing events, parametrized with respect to the wettability, hysteresis of the surface, and the Weber number. The present measurements provide the fundamental insights of the bouncing droplet impact dynamics and show that the coated face shield is potentially more effective in suppressing the airborne and fomite transmission.
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Affiliation(s)
- Bibek Kumar
- Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Sanghamitro Chatterjee
- Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Amit Agrawal
- Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Rajneesh Bhardwaj
- Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India
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33
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Hetherington R, Toufique Hasan ABM, Khan A, Roy D, Salehin M, Wadud Z. Exposure risk analysis of COVID-19 for a ride-sharing motorbike taxi. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:113319. [PMID: 35002199 PMCID: PMC8726634 DOI: 10.1063/5.0069454] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 10/27/2021] [Indexed: 05/31/2023]
Abstract
A dominant mode of transmission for the respiratory disease COVID-19 is via airborne virus-carrying aerosols. As national lockdowns are lifted and people begin to travel once again, an assessment of the risk associated with different forms of public transportation is required. This paper assesses the risk of transmission in the context of a ride-sharing motorbike taxi-a popular choice of paratransit in South and South-East Asia and Sub-Saharan Africa. Fluid dynamics plays a significant role in understanding the fate of droplets ejected from a susceptible individual during a respiratory event, such as coughing. Numerical simulations are employed here using an Eulerian-Lagrangian approach for particles and the Reynolds-averaged Navier-Stokes method for the background air flow. The driver is assumed to be exhaling virus laden droplets, which are transported toward the passenger by the background flow. A single cough is simulated for particle sizes 1, 10, 50 μ m , with motorbike speeds 1 , 5 , 15 m / s . It has been shown that small and large particles pose different types of risk. Depending on the motorbike speed, large particles may deposit onto the passenger, while smaller particles travel between the riders and may be inhaled by the passenger. To reduce risk of transmission to the passenger, a shield is placed between the riders. The shield not only acts as a barrier to block particles, but also alters the flow field around the riders, pushing particles away from the passenger. The findings of this paper therefore support the addition of a shield potentially making the journey safer.
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Affiliation(s)
- R. Hetherington
- School of Civil Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - A. B. M. Toufique Hasan
- Department of Mechanical Engineering, Bangladesh University of Engineering and Technology (BUET), Dhaka, Bangladesh
| | - A. Khan
- School of Civil Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - D. Roy
- Department of Mechanical Engineering, Bangladesh University of Engineering and Technology (BUET), Dhaka, Bangladesh
| | - M. Salehin
- Department of Mechanical Engineering, Bangladesh University of Engineering and Technology (BUET), Dhaka, Bangladesh
| | - Z. Wadud
- Institute for Transport Studies and School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom
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34
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Numerical Simulation of the Novel Coronavirus Spread in Commercial Aircraft Cabin. Processes (Basel) 2021. [DOI: 10.3390/pr9091601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Passengers carrying the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in a commercial aircraft cabin may infect other passengers and the cabin crew. In this study, a cabin model of the seven-row Airbus A320 aircraft is constructed and meshed for simulating the SARS-CoV-2 spread in the cabin with a virus carrier using the Computational Fluid Dynamics (CFD) modeling tool. The passengers’ infection risk is also quantified with the susceptible exposure index (SEI) method. The results show that the virus spreads to the ceiling of the cabin within 50 s of the virus carrier’s normal breathing. Coughing makes the virus spread to the front three rows with a higher mass fraction. While the high mass fraction areas always stay on the same side of the aisle as the virus carrier, the adjacent passengers and the passengers in the back two rows are affected more than the others when the virus carrier breathes normally. Spread patterns under the carrier’s two breath conditions, normal breath and cough, were numerically simulated.
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35
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Sen N, Singh KK. Spread of virus laden aerosols inside a moving sports utility vehicle with open windows: A numerical study. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:095117. [PMID: 34588759 PMCID: PMC8474020 DOI: 10.1063/5.0061753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 08/04/2021] [Indexed: 05/06/2023]
Abstract
A three dimensional Computational Fluid Dynamics (CFD) model to study the dispersion of virus laden aerosols in a car moving with its windows open is reported. The aerosols are generated when a possibly infected passenger speaks. A sports utility vehicle having three rows of seats has been considered. As the vehicle moves forward, its interior will exchange air from the surroundings. The CFD model captures the flow patterns generated both outside and inside the vehicle. This internal aerodynamics will in turn dictate how aerosols will spread across the interior and whether or not they will be transported outside the vehicle. A Lagrangian approach is used to determine the transport of the aerosol particles and the effect of particle size on the simulation result has been studied. Four sets of scenarios of practical interest have been considered. The first set shows the effect of vehicle speed on aerosol transport, and the second set describes what happens when some of the windows are closed, while the third set describes how aerosol transport is affected by the location of the passenger speaking. The fourth set describes how a gush of cross wind affects aerosol transport. Simulation results reveal that when all windows are open, aerosols can go out of one window and then return back to the vehicle interior through another window. Results also reveal that when a passenger sitting in the second row speaks, the aerosols generated span across the entire volume of the car interior before going out through the open windows.
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Affiliation(s)
- Nirvik Sen
- Chemical Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
| | - K. K. Singh
- Authors to whom correspondence should be addressed: and
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36
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Peña-Monferrer C, Antao S, Manson-Sawko R. Numerical investigation of respiratory drops dynamics released during vocalization. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:083321. [PMID: 34471339 PMCID: PMC8404381 DOI: 10.1063/5.0059419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 08/01/2021] [Indexed: 05/14/2023]
Abstract
Release of drops from a human body has been the focus of many recent investigations because of the current COVID-19 pandemic. Indirect virus transmission from asymptomatic individuals has been proved to be one of the major infectious routes and difficult to quantify, detect, and mitigate. We show in this work a detailed and novel numerical investigation of drops released during vocalization from a thermal manikin using a large eddy simulation coupled with Lagrangian tracking of drops. The vocalization experiment was modeled using existing data from the literature for modeling exhaled airflow, emission rate, and size distribution. Particular focus was on the definition of the boundary conditions for the exhalation process. Turbulence was compared with experimental data for the near mouth region for 75 exhalation breathing cycles and showed the sensitivity of different modeling assumptions at the mouth inlet. The results provide insights of special interest for understanding drop dynamics in speech-like exhalation modes, modeling the mouth inlet boundary conditions, and providing data for verifying other more simplified models.
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Affiliation(s)
- C. Peña-Monferrer
- IBM Research Europe, The Hartree Centre, Warrington WA4 4Ad, United Kingdom
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37
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Islam MS, Larpruenrudee P, Saha SC, Pourmehran O, Paul AR, Gemci T, Collins R, Paul G, Gu Y. How severe acute respiratory syndrome coronavirus-2 aerosol propagates through the age-specific upper airways. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:081911. [PMID: 34552312 PMCID: PMC8450910 DOI: 10.1063/5.0061627] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 07/24/2021] [Indexed: 05/22/2023]
Abstract
The recent outbreak of the COVID-19 causes significant respirational health problems, including high mortality rates worldwide. The deadly corona virus-containing aerosol enters the atmospheric air through sneezing, exhalation, or talking, assembling with the particulate matter, and subsequently transferring to the respiratory system. This recent outbreak illustrates that the severe acute respiratory syndrome (SARS) coronavirus-2 is deadlier for aged people than for other age groups. It is evident that the airway diameter reduces with age, and an accurate understanding of SARS aerosol transport through different elderly people's airways could potentially help the overall respiratory health assessment, which is currently lacking in the literature. This first-ever study investigates SARS COVID-2 aerosol transport in age-specific airway systems. A highly asymmetric age-specific airway model and fluent solver (ANSYS 19.2) are used for the investigation. The computational fluid dynamics measurement predicts higher SARS COVID-2 aerosol concentration in the airway wall for older adults than for younger people. The numerical study reports that the smaller SARS coronavirus-2 aerosol deposition rate in the right lung is higher than that in the left lung, and the opposite scenario occurs for the larger SARS coronavirus-2 aerosol rate. The numerical results show a fluctuating trend of pressure at different generations of the age-specific model. The findings of this study would improve the knowledge of SARS coronavirus-2 aerosol transportation to the upper airways which would thus ameliorate the targeted aerosol drug delivery system.
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Affiliation(s)
- Mohammad S. Islam
- School of Mechanical and Mechatronic Engineering, University of Technology Sydney (UTS), 15 Broadway, Ultimo, New South Wales 2007, Australia
- Authors to whom correspondence should be addressed: and
| | - Puchanee Larpruenrudee
- School of Mechanical and Mechatronic Engineering, University of Technology Sydney (UTS), 15 Broadway, Ultimo, New South Wales 2007, Australia
| | - Suvash C. Saha
- School of Mechanical and Mechatronic Engineering, University of Technology Sydney (UTS), 15 Broadway, Ultimo, New South Wales 2007, Australia
- Authors to whom correspondence should be addressed: and
| | - Oveis Pourmehran
- School of Mechanical Engineering, The University of Adelaide, Adelaide, South Australia 5005, Australia and Department of Surgery—Otolaryngology Head and Neck Surgery, The University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Akshoy Ranjan Paul
- Department of Applied Mechanics, Motilal Nehru National Institute of Technology Allahabad, Prayagraj 211004, Uttar Pradesh, India
| | | | - Richard Collins
- Biomechanics International, Cranberry Township, Pennsylvania 16066, USA
| | - Gunther Paul
- James Cook University, Australian Institute of Tropical Health and Medicine, Townsville, Queensland 4810, Australia
| | - Yuantong Gu
- School of Mechanical, Medical and Process Engineering, Faculty of Engineering, Queensland University of Technology, Brisbane 4000, Australia
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38
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Zhang Z, Capecelatro J, Maki K. On the utility of a well-mixed model for predicting disease transmission on an urban bus. AIP ADVANCES 2021; 11:085229. [PMID: 34466279 PMCID: PMC8404159 DOI: 10.1063/5.0061219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 08/04/2021] [Indexed: 05/06/2023]
Abstract
The transport of virus-laden aerosols from a host to a susceptible person is governed by complex turbulent airflow and physics related to breathing, coughing and sneezing, mechanical and passive ventilation, thermal buoyancy effects, surface deposition, masks, and air filtration. In this paper, we study the infection risk via airborne transmission on an urban bus using unsteady Reynolds-averaged Navier-Stokes equations and a passive-scalar model of the virus-laden aerosol concentration. Results from these simulations are directly compared to the widely used well-mixed model and show significant differences in the concentration field and number of inhaled particles. Specifically, in the limit of low mechanical ventilation rates, the well-mixed model will overpredict the concentration far from the infected passenger and substantially underpredict the concentration near the infected passenger. The results reported herein also apply to other enclosed spaces.
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Affiliation(s)
- Zhihang Zhang
- Department of Naval Architecture and Marine
Engineering, University of Michigan, Ann Arbor, Michigan 48109-2145,
USA
| | - Jesse Capecelatro
- Department of Mechanical Engineering, University
of Michigan, Ann Arbor, Michigan 48109-2145, USA
| | - Kevin Maki
- Department of Naval Architecture and Marine
Engineering, University of Michigan, Ann Arbor, Michigan 48109-2145,
USA
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39
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Ooi CC, Suwardi A, Ou Yang ZL, Xu G, Tan CKI, Daniel D, Li H, Ge Z, Leong FY, Marimuthu K, Ng OT, Lim SB, Lim P, Mak WS, Cheong WCD, Loh XJ, Kang CW, Lim KH. Risk assessment of airborne COVID-19 exposure in social settings. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:087118. [PMID: 34552314 PMCID: PMC8450907 DOI: 10.1063/5.0055547] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 08/09/2021] [Indexed: 05/04/2023]
Abstract
The COVID-19 pandemic has led to many countries oscillating between various states of lock-down as they seek to balance keeping the economy and essential services running and minimizing the risk of further transmission. Decisions are made about which activities to keep open across a range of social settings and venues guided only by ad hoc heuristics regarding social distancing and personal hygiene. Hence, we propose the dual use of computational fluid dynamic simulations and surrogate aerosol measurements for location-specific assessment of risk of infection across different real-world settings. We propose a 3-tiered risk assessment scheme to facilitate classification of scenarios into risk levels based on simulations and experiments. Threshold values of <54 and >840 viral copies and <5% and >40% of original aerosol concentration are chosen to stratify low, medium, and high risk. This can help prioritize allowable activities and guide implementation of phased lockdowns or re-opening. Using a public bus in Singapore as a case study, we evaluate the relative risk of infection across scenarios such as different activities and passenger positions and demonstrate the effectiveness of our risk assessment methodology as a simple and easily interpretable framework. For example, this study revealed that the bus's air-conditioning greatly influences dispersion and increases the risk of certain seats and that talking can result in similar relative risk to coughing for passengers around an infected person. Both numerical and experimental approaches show similar relative risk levels with a Spearman's correlation coefficient of 0.74 despite differing observables, demonstrating applicability of this risk assessment methodology to other scenarios.
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Affiliation(s)
- Chin Chun Ooi
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, Singapore 138632
| | - Ady Suwardi
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 2 Fusionopolis Way, Singapore 138634
| | - Zhong Liang Ou Yang
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, Singapore 138632
| | - George Xu
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, Singapore 138632
| | - Chee Kiang Ivan Tan
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 2 Fusionopolis Way, Singapore 138634
| | - Dan Daniel
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 2 Fusionopolis Way, Singapore 138634
| | - Hongying Li
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, Singapore 138632
| | - Zhengwei Ge
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, Singapore 138632
| | - Fong Yew Leong
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, Singapore 138632
| | - Kalisvar Marimuthu
- National Centre for Infectious Diseases, Tan Tock Seng Hospital, 16 Jalan Tan Tock Seng, Singapore 308443
| | - Oon Tek Ng
- National Centre for Infectious Diseases, Tan Tock Seng Hospital, 16 Jalan Tan Tock Seng, Singapore 308443
| | - Shin Bin Lim
- Ministry of Health Singapore, College of Medicine Building, 16 College Road, Singapore 169854
| | - Peter Lim
- Land Transport Authority, 1 Hampshire Road, Singapore 219428
| | - Wai Siong Mak
- Land Transport Authority, 1 Hampshire Road, Singapore 219428
| | - Wun Chet Davy Cheong
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 2 Fusionopolis Way, Singapore 138634
| | - Xian Jun Loh
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 2 Fusionopolis Way, Singapore 138634
| | - Chang Wei Kang
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, Singapore 138632
| | - Keng Hui Lim
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, Singapore 138632
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40
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The Role of HVAC Design and Windows on the Indoor Airflow Pattern and ACH. SUSTAINABILITY 2021. [DOI: 10.3390/su13147931] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The purpose of heating, ventilation, and air conditioning (HVAC) systems are to create optimum thermal comfort and appropriate indoor air quality (IAQ) for occupants. Air ventilation systems can significantly affect the health risk in indoor environments, especially those by contaminated aerosols. Therefore, the main goal of the study is to analyze the indoor airflow patterns in the heating, ventilation, and air conditioning (HVAC) systems and the impact of outlets/windows. The other goal of this study is to simulate the trajectory of the aerosols from a human sneeze, investigate the impact of opening windows on the number of air changes per hour (ACH) and exhibit the role of dead zones with poor ventilation. The final goal is to show the application of computational fluid dynamics (CFD) simulation in improving the HVAC design, such as outlet locations or airflow rate, in addition to the placement of occupants. In this regard, an extensive literature review has been combined with the CFD method to analyze the indoor airflow patterns, ACH, and the role of windows. The airflow pattern analysis shows the critical impact of inflow/outflow and windows. The results show that the CFD model simulation could exhibit optimal placement and safer locations for the occupants to decrease the health risk. The results of the discrete phase simulation determined that the actual ACH could be different from the theoretical ACH as the short circuit and dead zones affect the ACH.
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CFD Investigation of Vehicle’s Ventilation Systems and Analysis of ACH in Typical Airplanes, Cars, and Buses. SUSTAINABILITY 2021. [DOI: 10.3390/su13126799] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The simulation of the ventilation and the heating, ventilation, and air conditioning (HVAC) systems of vehicles could be used in the energy demand management of vehicles besides improving the air quality inside their cabins. Moreover, traveling by public transport during a pandemic is a concerning factor, and analysis of the vehicle’s cabin environments could demonstrate how to decrease the risk and create a safer journey for passengers. Therefore, this article presents airflow analysis, air changes per hour (ACH), and respiration aerosols’ trajectory inside three vehicles, including a typical car, bus, and airplane. In this regard, three vehicles’ cabin environment boundary conditions and the HVAC systems of the selected vehicles were determined, and three-dimensional numerical simulations were performed using computational fluid dynamic (CFD) modeling. The analysis of the airflow patterns and aerosol trajectories in the selected vehicles demonstrate the critical impact of inflow, outflow, and passenger’s locations in the cabins. The CFD model results exhibited that the lowest risk could be in the airplane and the highest in the bus because of the location of airflows and outflows. The discrete CFD model analysis determined the ACH for a typical car of about 4.3, a typical bus of about 7.5, and in a typical airplane of about 8.5, which were all less than the standard protocol of infection prevention, 12 ACH. According to the results, opening windows in the cars could decrease the aerosol loads and improve the low ACH by the HVAC systems. However, for the buses, a new design for the outflow location or an increase in the number of outflows appeared necessary. In the case of airplanes, the airflow paths were suitable, and by increasing the airflow speed, the required ACH might be achieved. Finally, in the closed (recirculating) systems, the role of filters in decreasing the risk appeared critical.
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Mirikar D, Palanivel S, Arumuru V. Droplet fate, efficacy of face mask, and transmission of virus-laden droplets inside a conference room. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:065108. [PMID: 34248325 PMCID: PMC8232678 DOI: 10.1063/5.0054110] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 05/13/2021] [Indexed: 05/16/2023]
Abstract
The second and third waves of coronavirus disease-2019 (COVID-19) pandemic have hit the world. Even after more than a year, the economy is yet to return to a semblance of normality. The conference/meeting room is one of the critical sections of offices that might be difficult not to use. This study analyzes the distribution of the virus-laden droplets expelled by coughing inside a conference room, the effect of ventilation rates, and their positioning. The efficacy of masks is studied to get quantitative information regarding the residence time of the droplets. The effects of evaporation, turbulent dispersion, and external forces have been considered for calculating the droplets' trajectories. We have analyzed six cases, of which two are with masks. Change in the ventilation rate from four air changes per hour (ACH) to eight resulted in a 9 % increment in the number of droplets entrained in the outlet vent, while their average residence time was reduced by ∼ 8 s . The shift in the vents' location has significantly altered droplets' distribution inside a conference room. It results in ∼ 1.5 % of the injected droplets reaching persons sitting across the table, and a similar indoor environment is not recommended. Wearing a mask in the case of eight ACH has presented the best scenario out of the six cases, with a 6.5 % improvement in the number of droplets entrained in the outlet vent and a 9 s decrease in their average residence time compared to the case without a mask. No droplets have reached persons sitting across the table when the infected person is wearing the mask, which follows that a social distancing of 6 ft with a mask is adequate in indoor environments.
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Affiliation(s)
- Dnyanesh Mirikar
- Applied Fluids Group, School of Mechanical Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar 752050, India
| | - Silambarasan Palanivel
- Applied Fluids Group, School of Mechanical Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar 752050, India
| | - Venugopal Arumuru
- Applied Fluids Group, School of Mechanical Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar 752050, India
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Zheng J, Wu X, Fang F, Li J, Wang Z, Xiao H, Zhu J, Pain C, Linden P, Xiang B. Numerical study of COVID-19 spatial-temporal spreading in London. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:046605. [PMID: 33953530 PMCID: PMC8086595 DOI: 10.1063/5.0048472] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 03/27/2021] [Indexed: 05/05/2023]
Abstract
A recent study reported that an aerosolized virus (COVID-19) can survive in the air for a few hours. It is highly possible that people get infected with the disease by breathing and contact with items contaminated by the aerosolized virus. However, the aerosolized virus transmission and trajectories in various meteorological environments remain unclear. This paper has investigated the movement of aerosolized viruses from a high concentration source across a dense urban area. The case study looks at the highly air polluted areas of London: University College Hospital (UCH) and King's Cross and St Pancras International Station (KCSPI). We explored the spread and decay of COVID-19 released from the hospital and railway stations with the prescribed meteorological conditions. The study has three key findings: the primary result is that the concentration of viruses decreases rapidly by a factor of 2-3 near the sources although the virus may travel from meters up to hundreds of meters from the source location for certain meteorological conditions. The secondary finding shows viruses released into the atmosphere from entry and exit points at KCSPI remain trapped within a small radial distance of < 50 m. This strengthens the case for the use of face coverings to reduce the infection rate. The final finding shows that there are different levels of risk at various door locations for UCH; depending on which door is used there can be a higher concentration of COVID-19. Although our results are based on London, since the fundamental knowledge processes are the same, our study can be further extended to other locations (especially the highly air polluted areas) in the world.
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Affiliation(s)
- Jie Zheng
- Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
| | - Xiaofei Wu
- Applied Modelling and Computation Group, Department of Earth Science and Engineering, Imperial College London, Prince Consort Road, London SW7 2AZ, United Kingdom
| | - Fangxin Fang
- Applied Modelling and Computation Group, Department of Earth Science and Engineering, Imperial College London, Prince Consort Road, London SW7 2AZ, United Kingdom
| | | | - Zifa Wang
- State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
| | - Hang Xiao
- Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
| | | | - Christopher Pain
- Applied Modelling and Computation Group, Department of Earth Science and Engineering, Imperial College London, Prince Consort Road, London SW7 2AZ, United Kingdom
| | - Paul Linden
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge, England CB3 0WA, United Kingdom
| | - Boyu Xiang
- Wilson's School, Mollison Drive, Wallington, Surrey SM6 9JW, United Kingdom
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