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Berlanga FA, Gomez P, Esteban A, Liu L, Nielsen PV. Three dimensional analysis of the exhalation flow in the proximity of the mouth. Heliyon 2024; 10:e26283. [PMID: 38434078 PMCID: PMC10906307 DOI: 10.1016/j.heliyon.2024.e26283] [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: 08/01/2023] [Revised: 02/02/2024] [Accepted: 02/09/2024] [Indexed: 03/05/2024] Open
Abstract
The human exhalation flow is characterized in this work from the three-dimensional velocimetry results obtained by using the stereo particle image velocimetry (SPIV) measurement technique on the flow emitted from a realistic airway model. For this purpose, the transient exhalation flow through the mouth of a person performing two different breaths corresponding to two metabolic rates, standing relaxed (SR) and walking active (WA), is emulated and studied. To reproduce the flow realistically, a detailed three-dimensional model obtained from computed tomography measurements on real subjects is used. To cope with the variability of the experimental data, a subsequent analysis of the results is performed using the TR-PIV (time resolved particle image velocimetry) technique. Exhalation produces a transient jet that becomes a puff when flow emission ends. Three-dimensional vector fields of the jet velocity are obtained in five equally spaced transverse planes up to a distance of Image 1 from the mouth at equally spaced time instants Image 2 which will be referred to as phases (φ), from the beginning to the end of exhalation. The time evolution during exhalation of the jet area of influence, the velocity field and the jet air entrainment have been characterized for each of the jet cross sections. The importance of the use of realistic airway models for the study of this type of flow and the influence of the metabolic rate on its development are also analyzed. The results obtained contribute to the characterization of the human exhalation as a pathway of the transmission of pathogens such as SARS-CoV-2 virus.
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Affiliation(s)
- F A Berlanga
- Dept. de Mecánica, ETSII, Universidad Nacional de Educación a Distancia (UNED), E-28040, Madrid, Spain
| | - P Gomez
- Dept. de Mecánica, ETSII, Universidad Nacional de Educación a Distancia (UNED), E-28040, Madrid, Spain
| | - A Esteban
- Dept. de Mecánica, ETSII, Universidad Nacional de Educación a Distancia (UNED), E-28040, Madrid, Spain
| | - L Liu
- Dept. of Building Science and Technology, School of Architecture, Tsinghua University, Haidian District, Beijing, China
| | - P V Nielsen
- Dept. of the Built Environment, Aalborg Universitet, Thomas Manns Vej 23 9220 Aalborg Øst, Denmark
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2
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Sheikhnejad Y, Aghamolaei R, Fallahpour M, Motamedi H, Moshfeghi M, Mirzaei PA, Bordbar H. Airborne and aerosol pathogen transmission modeling of respiratory events in buildings: An overview of computational fluid dynamics. SUSTAINABLE CITIES AND SOCIETY 2022; 79:103704. [PMID: 35070645 PMCID: PMC8767784 DOI: 10.1016/j.scs.2022.103704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 01/13/2022] [Accepted: 01/15/2022] [Indexed: 05/03/2023]
Abstract
Pathogen droplets released from respiratory events are the primary means of dispersion and transmission of the recent pandemic of COVID-19. Computational fluid dynamics (CFD) has been widely employed as a fast, reliable, and inexpensive technique to support decision-making and to envisage mitigatory protocols. Nonetheless, the airborne pathogen droplet CFD modeling encounters limitations due to the oversimplification of involved physics and the intensive computational demand. Moreover, uncertainties in the collected clinical data required to simulate airborne and aerosol transport such as droplets' initial velocities, tempo-spatial profiles, release angle, and size distributions are broadly reported in the literature. There is a noticeable inconsistency around these collected data amongst many reported studies. This study aims to review the capabilities and limitations associated with CFD modeling. Setting the CFD models needs experimental data of respiratory flows such as velocity, particle size, and number distribution. Therefore, this paper briefly reviews the experimental techniques used to measure the characteristics of airborne pathogen droplet transmissions together with their limitations and reported uncertainties. The relevant clinical data related to pathogen transmission needed for postprocessing of CFD data and translating them to safety measures are also reviewed. Eventually, the uncertainty and inconsistency of the existing clinical data available for airborne pathogen CFD analysis are scurtinized to pave a pathway toward future studies ensuing these identified gaps and limitations.
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Affiliation(s)
- Yahya Sheikhnejad
- Centre for Mechanical Technology and Automation, Department of Mechanical Engineering, Universidade de Aveiro, Aveiro 3810-193, Portugal
- PICadvanced SA, Creative Science Park, Via do Conhecimento, Ed. Central, Ílhavo 3830-352, Portugal
| | - Reihaneh Aghamolaei
- School of Mechanical and Manufacturing Engineering, Faculty of Engineering and Computing, Dublin City University, Dublin 9, Whitehall, Ireland
| | - Marzieh Fallahpour
- School of Mechanical and Manufacturing Engineering, Faculty of Engineering and Computing, Dublin City University, Dublin 9, Whitehall, Ireland
| | - Hamid Motamedi
- Department of Mechanical Engineering, Tarbiat Modares University, Iran
| | - Mohammad Moshfeghi
- Department of Mechanical Engineering, Sogang University, Seoul, South Korea
| | - Parham A Mirzaei
- Architecture & Built Environment Department, University of Nottingham, University Park, Nottingham, UK
| | - Hadi Bordbar
- School of Engineering, Aalto University, Finland
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3
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El Hassan M, Assoum H, Bukharin N, Al Otaibi H, Mofijur M, Sakout A. A review on the transmission of COVID-19 based on cough/sneeze/breath flows. EUROPEAN PHYSICAL JOURNAL PLUS 2021; 137:1. [PMID: 34909366 PMCID: PMC8660964 DOI: 10.1140/epjp/s13360-021-02162-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 11/08/2021] [Indexed: 05/17/2023]
Abstract
COVID-19 pandemic has recently had a dramatic impact on society. The understanding of the disease transmission is of high importance to limit its spread between humans. The spread of the virus in air strongly depends on the flow dynamics of the human airflows. It is, however, known that predicting the flow dynamics of the human airflows can be challenging due to different particles sizes and the turbulent aspect of the flow regime. It is thus recommended to present a deep analysis of different human airflows based on the existing experimental investigations. A validation of the existing numerical predictions of such flows would be of high interest to further develop the existing numerical model for different flow configurations. This paper presents a literature review of the experimental and numerical studies on human airflows, including sneezing, coughing and breathing. The dynamics of these airflows for different droplet sizes is discussed. The influence of other parameters, such as the viscosity and relative humidity, on the germs transmission is also presented. Finally, the efficacy of using a facemask in limiting the transmission of COVID-19 is investigated.
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Affiliation(s)
- Mouhammad El Hassan
- Mechanical Engineering Department, Prince Mohammad Bin Fahd University, Al Khobar, Kingdom of Saudi Arabia
| | - Hassan Assoum
- Mechanical Engineering Department, Beirut Arab University, Tripoli, Lebanon
| | - Nikolay Bukharin
- School of Manufacturing and Automation, Southern Alberta Institute of Technology, Calgary, Canada
| | - Huda Al Otaibi
- Mechanical Engineering Department, Prince Mohammad Bin Fahd University, Al Khobar, Kingdom of Saudi Arabia
| | - Md Mofijur
- Mechanical Engineering Department, Prince Mohammad Bin Fahd University, Al Khobar, Kingdom of Saudi Arabia
- Faculty of Engineering and Information Technology, University of Technology Sydney, Sydney, NSW 2007 Australia
| | - Anas Sakout
- LASIE, University of La Rochelle, La Rochelle, France
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4
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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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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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Yu J, Kim C, Lee YG, Bae S. Impact on airborne virus behavior by an electric heat pump (EHP) operation in a restaurant during winter season. BUILDING AND ENVIRONMENT 2021; 200:107951. [PMID: 36570050 PMCID: PMC9758606 DOI: 10.1016/j.buildenv.2021.107951] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Revised: 04/30/2021] [Accepted: 05/05/2021] [Indexed: 06/14/2023]
Abstract
The world is having an unprecedented time due to the pandemic. Currently, more than 93 million people have been infected, and over 2 million people have passed away since 2020. SARS-CoV-2 has forced people to change their lifestyles and patterns. Under the pandemic, buildings are no longer safe shelters. The infected transmit infectious viruses to other occupants by direct contact or indirect contact (i.e., indoor airflow). In addition, the airflow from electric heat pump systems can propel indirect contact in indoor spaces. However, the impact of airflow is still not sufficiently identified to develop virus control strategies in buildings. Therefore, this study selected a restaurant in Seoul, Korea, to experiment with airborne virus transmission of direct airflow in winter using virus-similar particles. The results of this study verified the potential exposure of droplets or aerosols to occupants that can be delivered by air current from heating systems in winter. The effect of kitchen hoods was also confirmed as additional ventilation equipment without additional budget investment in restaurants. The recommendations of this study are expected to improve the guidelines for restaurants to ensure occupant's safety during the COVID-19 period.
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Affiliation(s)
- Jungyeon Yu
- Indoor Air Quality Research Center, Korea Institute of Civil Engineering and Building Technology, Goyang-Si, 10223, South Korea
| | - Chul Kim
- Indoor Air Quality Research Center, Korea Institute of Civil Engineering and Building Technology, Goyang-Si, 10223, South Korea
| | - Yun Gyu Lee
- Indoor Air Quality Research Center, Korea Institute of Civil Engineering and Building Technology, Goyang-Si, 10223, South Korea
| | - Sanghwan Bae
- Indoor Air Quality Research Center, Korea Institute of Civil Engineering and Building Technology, Goyang-Si, 10223, South Korea
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Mahjoub Mohammed Merghani K, Sagot B, Gehin E, Da G, Motzkus C. A review on the applied techniques of exhaled airflow and droplets characterization. INDOOR AIR 2021; 31:7-25. [PMID: 33206424 PMCID: PMC7753802 DOI: 10.1111/ina.12770] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 10/12/2020] [Accepted: 11/01/2020] [Indexed: 05/18/2023]
Abstract
In the last two decades, multidisciplinary research teams worked on developing a comprehensive understanding of the transmission mechanisms of airborne diseases. This article reviews the experimental studies on the characterization of the exhaled airflow and the droplets, comparing the measured parameters, the advantages, and the limitations of each technique. To characterize the airflow field, the global flow-field techniques-high-speed photography, schlieren photography, and PIV-are applied to visualize the shape and propagation of the exhaled airflow and its interaction with the ambient air, while the pointwise measurements provide quantitative measurements of the velocity, flow rate, humidity and temperature at a single point in the flow field. For the exhaled droplets, intrusive techniques are used to characterize the size distribution and concentration of the droplets' dry residues while non-intrusive techniques can measure the droplet size and velocity at different locations in the flow field. The evolution of droplets' size and velocity away from the source has not yet been thoroughly experimentally investigated. Besides, there is a lack of information about the temperature and humidity fields composed by the interaction of the exhaled airflow and the ambient air.
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Near-Field Flow Structure and Entrainment of a Round Jet at Low Exit Velocities: Implications on Microclimate Ventilation. COMPUTATION 2020. [DOI: 10.3390/computation8040100] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
This paper explores the flow structure, mean/turbulent statistical characteristics of the vector field and entrainment of round jets issued from a smooth contracting nozzle at low nozzle exit velocities (1.39–6.44 m/s). The motivation of the study was to increase understand of the near field and get insights on how to control and reduce entrainment, particularly in applications that use jets with low-medium momentum flow like microclimate ventilation systems. Additionally, the near field of free jets with low momentum flow is not extensively covered in literature. Particle image velocimetry (PIV), a whole field vector measurement method, was used for data acquisition of the flow from a 0.025 m smooth contracting nozzle. The results show that at low nozzle exit velocities the jet flow was unstable with oscillations and this increased entrainment, however, increasing the nozzle exit velocity stabilized the jet flow and reduced entrainment. This is linked to the momentum flow of the jet, the structure characteristics of the flow and the type or disintegration distance of vortices created on the shear layer. The study discusses practical implications on microclimate ventilation systems and at the same time contributes data to the development and validation of a planned computational turbulence model for microclimate ventilation.
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9
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Speech can produce jet-like transport relevant to asymptomatic spreading of virus. Proc Natl Acad Sci U S A 2020; 117:25237-25245. [PMID: 32978297 DOI: 10.1073/pnas.2012156117] [Citation(s) in RCA: 111] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Many scientific reports document that asymptomatic and presymptomatic individuals contribute to the spread of COVID-19, probably during conversations in social interactions. Droplet emission occurs during speech, yet few studies document the flow to provide the transport mechanism. This lack of understanding prevents informed public health guidance for risk reduction and mitigation strategies, e.g., the "6-foot rule." Here we analyze flows during breathing and speaking, including phonetic features, using orders-of-magnitude estimates, numerical simulations, and laboratory experiments. We document the spatiotemporal structure of the expelled airflow. Phonetic characteristics of plosive sounds like "P" lead to enhanced directed transport, including jet-like flows that entrain the surrounding air. We highlight three distinct temporal scaling laws for the transport distance of exhaled material including 1) transport over a short distance (<0.5 m) in a fraction of a second, with large angular variations due to the complexity of speech; 2) a longer distance, ∼1 m, where directed transport is driven by individual vortical puffs corresponding to plosive sounds; and 3) a distance out to about 2 m, or even farther, where sequential plosives in a sentence, corresponding effectively to a train of puffs, create conical, jet-like flows. The latter dictates the long-time transport in a conversation. We believe that this work will inform thinking about the role of ventilation, aerosol transport in disease transmission for humans and other animals, and yield a better understanding of linguistic aerodynamics, i.e., aerophonetics.
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Kabanshi A, Sandberg M. Entrainment and its implications on microclimate ventilation systems: Scaling the velocity and temperature field of a round free jet. INDOOR AIR 2019; 29:331-346. [PMID: 30500986 DOI: 10.1111/ina.12524] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 11/23/2018] [Accepted: 11/24/2018] [Indexed: 06/09/2023]
Abstract
Research on microclimate ventilation systems, which mostly involve free jets, points to delivery of better ventilation in breathing zones. While the literature is comprehensive, the influence of contaminant entrainment in jet flows and its implications on the delivery of supplied air is not fully addressed. This paper presents and discusses entrainment characteristics of a jet issued from a round nozzle (0.05 m diameter), in relation to ventilation, by exploring the velocity and temperature fields of the jet flow. The results show a trend suggesting that increasing the Reynold number (Re) reduces ambient entrainment. As shown herein, about 30% concentration of ambient air entrained into the bulk jet flow at Re 2541 while Re 9233 had about 13% and 19% for Re = 6537/12 026 at downstream distance of 8 diameters (40 cm). The study discusses that "moderate to high" Re may be ideal to reduce contaminant entrainment, but this is limited by delivery distance and possibly the risk of occupant discomfort. Incorporating the entrainment mixing factor (the ratio of room contaminants entrained into a jet flow) in performance measurements is proposed, and further studies are recommended to verify results herein and test whether this is general to other nozzle configurations.
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Affiliation(s)
- Alan Kabanshi
- Department of Building, Energy and Environmental Engineering, University of Gävle, Gävle, Sweden
| | - Mats Sandberg
- Department of Building, Energy and Environmental Engineering, University of Gävle, Gävle, Sweden
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Ai ZT, Melikov AK. Airborne spread of expiratory droplet nuclei between the occupants of indoor environments: A review. INDOOR AIR 2018; 28:500-524. [PMID: 29683213 DOI: 10.1111/ina.12465] [Citation(s) in RCA: 91] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2017] [Accepted: 04/13/2018] [Indexed: 05/04/2023]
Abstract
This article reviews past studies of airborne transmission between occupants in indoor environments, focusing on the spread of expiratory droplet nuclei from mouth/nose to mouth/nose for non-specific diseases. Special attention is paid to summarizing what is known about the influential factors, the inappropriate simplifications of the thermofluid boundary conditions of thermal manikins, the challenges facing the available experimental techniques, and the limitations of available evaluation methods. Secondary issues are highlighted, and some new ways to improve our understanding of airborne transmission indoors are provided. The characteristics of airborne spread of expiratory droplet nuclei between occupants, which are influenced correlatively by both environmental and personal factors, were widely revealed under steady-state conditions. Owing to the different boundary conditions used, some inconsistent findings on specific influential factors have been published. The available instrumentation was too slow to provide accurate concentration profiles for time-dependent evaluations of events with obvious time characteristics, while computational fluid dynamics (CFD) studies were mainly performed in the framework of inherently steady Reynolds-averaged Navier-Stokes modeling. Future research needs in 3 areas are identified: the importance of the direction of indoor airflow patterns, the dynamics of airborne transmission, and the application of CFD simulations.
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Affiliation(s)
- Z T Ai
- Department of Civil Engineering, International Centre for Indoor Environment and Energy, Technical University of Denmark, Copenhagen, Denmark
| | - A K Melikov
- Department of Civil Engineering, International Centre for Indoor Environment and Energy, Technical University of Denmark, Copenhagen, Denmark
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Berlanga FA, Olmedo I, Ruiz de Adana M. Experimental analysis of the air velocity and contaminant dispersion of human exhalation flows. INDOOR AIR 2017; 27:803-815. [PMID: 27859708 DOI: 10.1111/ina.12357] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Accepted: 11/11/2016] [Indexed: 05/26/2023]
Abstract
Human exhalation flow is a potential source of pathogens that can constitute a cross-infection risk to people in indoor environments. Thus, it is important to investigate the characteristics of this flow, its development, area of influence, and the diffusion of the exhaled contaminants. This paper uses phase-averaged particle image velocimetry together with a tracer gas (CO2 ) to study two different exhalation flows over time: the exhalation of an average male (test M) and an average female (test F), using a life-sized thermal manikin in a supine position. The exhalation jets generated for both tests are similar in terms of symmetrical geometry, vorticity values, jet opening angles, and velocity and concentration decays. However, there is a difference in the penetration length of the two flows throughout the whole exhalation process. There is also a time difference in reaching maximum velocity between the two tests. It is also possible to see that the tracer gas dispersion depends on the momentum of the jet so the test with the highest velocity decay shows the lowest concentration decay. All these results are of interest to better understand cross-infection risk.
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Affiliation(s)
- F A Berlanga
- Department of Chemical Physics and Applied Thermodynamics, University of Córdoba, Córdoba, Spain
| | - I Olmedo
- Department of Chemical Physics and Applied Thermodynamics, University of Córdoba, Córdoba, Spain
| | - M Ruiz de Adana
- Department of Chemical Physics and Applied Thermodynamics, University of Córdoba, Córdoba, Spain
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Xu C, Nielsen PV, Liu L, Jensen RL, Gong G. Human exhalation characterization with the aid of schlieren imaging technique. BUILDING AND ENVIRONMENT 2017; 112:190-199. [PMID: 32287969 PMCID: PMC7111220 DOI: 10.1016/j.buildenv.2016.11.032] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Revised: 11/17/2016] [Accepted: 11/18/2016] [Indexed: 05/08/2023]
Abstract
The purpose of this paper is to determine the dispersion and distribution characteristics of exhaled airflow for accurate prediction of disease transmission. The development of airflow dynamics of human exhalation was characterized using nonhazardous schlieren photography technique, providing a visualization and quantification of turbulent exhaled airflow from 18 healthy human subjects whilst standing and lying. The flow shape of each breathing pattern was characterized by two angles and averaged values of 18 subjects. Two exhaled air velocities, u m and u p , were measured and compared. The mean peak centerline velocity, u m was found to decay correspondingly with increasing horizontal distance x in a form of power function. The mean propagation velocity, u p was found to correlate with physiological parameters of human subjects. This was always lower than u m at the mouth/nose opening, due to a vortex like airflow in front of a single exhalation cycle. When examining the talking and breathing process between two persons, the potential infectious risk was found to depend on their breathing patterns and spatial distribution of their exhaled air. Our study when combined with information on generation and distributions of pathogens could provide a prediction method and control strategy to minimize infection risk between persons in indoor environments.
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Affiliation(s)
- Chunwen Xu
- College of Pipeline and Civil Engineering, China University of Petroleum, Qingdao 266580, China
- Department of Civil Engineering, Aalborg University, Aalborg 9000, Denmark
| | - Peter V. Nielsen
- Department of Civil Engineering, Aalborg University, Aalborg 9000, Denmark
| | - Li Liu
- Department of Civil Engineering, Aalborg University, Aalborg 9000, Denmark
| | - Rasmus L. Jensen
- Department of Civil Engineering, Aalborg University, Aalborg 9000, Denmark
| | - Guangcai Gong
- College of Civil Engineering, Hunan University, Changsha 410082, China
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