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Nof E, Bhardwaj S, Koullapis P, Bessler R, Kassinos S, Sznitman J. In vitro-in silico correlation of three-dimensional turbulent flows in an idealized mouth-throat model. PLoS Comput Biol 2023; 19:e1010537. [PMID: 36952557 PMCID: PMC10072468 DOI: 10.1371/journal.pcbi.1010537] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 04/04/2023] [Accepted: 02/08/2023] [Indexed: 03/25/2023] Open
Abstract
There exists an ongoing need to improve the validity and accuracy of computational fluid dynamics (CFD) simulations of turbulent airflows in the extra-thoracic and upper airways. Yet, a knowledge gap remains in providing experimentally-resolved 3D flow benchmarks with sufficient data density and completeness for useful comparison with widely-employed numerical schemes. Motivated by such shortcomings, the present work details to the best of our knowledge the first attempt to deliver in vitro-in silico correlations of 3D respiratory airflows in a generalized mouth-throat model and thereby assess the performance of Large Eddy Simulations (LES) and Reynolds-Averaged Numerical Simulations (RANS). Numerical predictions are compared against 3D volumetric flow measurements using Tomographic Particle Image Velocimetry (TPIV) at three steady inhalation flowrates varying from shallow to deep inhalation conditions. We find that a RANS k-ω SST model adequately predicts velocity flow patterns for Reynolds numbers spanning 1'500 to 7'000, supporting results in close proximity to a more computationally-expensive LES model. Yet, RANS significantly underestimates turbulent kinetic energy (TKE), thus underlining the advantages of LES as a higher-order turbulence modeling scheme. In an effort to bridge future endevours across respiratory research disciplines, we provide end users with the present in vitro-in silico correlation data for improved predictive CFD models towards inhalation therapy and therapeutic or toxic dosimetry endpoints.
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Affiliation(s)
- Eliram Nof
- Department of Biomedical Engineering, Technion-Israel Institute of Technology, Haifa, Israel
| | - Saurabh Bhardwaj
- Department of Biomedical Engineering, Technion-Israel Institute of Technology, Haifa, Israel
| | - Pantelis Koullapis
- Computational Sciences Laboratory (UCY-CompSci), Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia, Cyprus
| | - Ron Bessler
- Department of Biomedical Engineering, Technion-Israel Institute of Technology, Haifa, Israel
| | - Stavros Kassinos
- Computational Sciences Laboratory (UCY-CompSci), Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia, Cyprus
| | - Josué Sznitman
- Department of Biomedical Engineering, Technion-Israel Institute of Technology, Haifa, Israel
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Sommerfeld M, Sgrott OL, Taborda MA, Koullapis P, Bauer K, Kassinos S. Analysis of flow field and turbulence predictions in a lung model applying RANS and implications for particle deposition. Eur J Pharm Sci 2021; 166:105959. [PMID: 34324962 DOI: 10.1016/j.ejps.2021.105959] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 07/16/2021] [Accepted: 07/24/2021] [Indexed: 10/20/2022]
Abstract
Airflow and aerosol deposition in the human airways are important aspects for applications such as pulmonary drug delivery and human exposure to aerosol pollutants. Numerical simulations are widely used nowadays to shed light in airflow features and particle deposition patterns inside the airways. For that purpose, the Euler/Lagrange approach is adopted for predicting flow field and particle deposition through point-particle tracking. Steady-state RANS (Reynolds-averaged Navier-Stokes) computations of flow evolution in an extended lung model applying different turbulence models were conducted and compared to measurements as well as high resolution LES (large-eddy simulations) for several flow rates. In addition, various inlet boundary conditions were considered and their influence on the predicted flow field was analysed. The results showed that the mean velocity field was simulated reasonably well, however, turbulence intensity was completely under-predicted by two-equation turbulence models. Only a Reynolds-stress model (RSM) was able predicting a turbulence level comparable to the measurements and the high resolution LES. Remarkable reductions in wall deposition were observed when wall effects were accounted for in the drag and lift force expressions. Naturally, turbulence is an essential contribution to particle deposition and it is well known that two-equation turbulence models considerably over-predict deposition due to the spurious drift effect. A full correction of this error is only possible in connection with a Reynolds-stress turbulence model whereby the predicted deposition in dependence of particle diameter yielded better agreement to the LES predictions. Specifically, with the RSM larger deposition is predicted for smaller particles and lower deposition fraction for larger particles compared to LES. The local deposition fraction along the lung model was numerically predicted with the same trend as found from the measurements, however the values in the middle region of the lung model were found to be somewhat larger.
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Affiliation(s)
- M Sommerfeld
- Multiphase Flow Systems (MPS), Otto-von-Guericke-University Magdeburg, Hoher Weg 7b, D-06120 Halle (Saale), Germany.
| | - O L Sgrott
- Multiphase Flow Systems (MPS), Otto-von-Guericke-University Magdeburg, Hoher Weg 7b, D-06120 Halle (Saale), Germany
| | - M A Taborda
- Multiphase Flow Systems (MPS), Otto-von-Guericke-University Magdeburg, Hoher Weg 7b, D-06120 Halle (Saale), Germany
| | - P Koullapis
- Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia, Cyprus.
| | - K Bauer
- Institute of Mechanics and Fluid Dynamics, TU Bergakademie Freiberg, Freiberg, Germany.
| | - S Kassinos
- Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia, Cyprus
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Christou S, Chatziathanasiou T, Angeli S, Koullapis P, Stylianou F, Sznitman J, Guo HH, Kassinos SC. Anatomical variability in the upper tracheobronchial tree: sex-based differences and implications for personalized inhalation therapies. J Appl Physiol (1985) 2020; 130:678-707. [PMID: 33180641 DOI: 10.1152/japplphysiol.00144.2020] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The morphometry of the large conducting airways is presumed to have a strong effect on the regional deposition of inhaled aerosol particles. Nevertheless, sex-based differences have not been fully quantified and are still largely ignored in designing inhalation therapies. To this end, we retrospectively analyzed high-resolution computed tomography scans for 185 individuals (90 women, 95 men) in the age range of 12-89 yr to determine airway luminal areas, airway lengths, and bifurcation angles. Only subjects free of chronic airway disease were considered. In men, luminal areas of the upper conducting airways were, on average, ∼30%-50% larger when compared with those in women, with the largest differences found in the trachea (289.72 ± 54.25 vs. 193.50 ± 42.37 mm2 for men and women, respectively). The ratio of the largest luminal area in men to the smallest luminal area in women (in any given segment) ranged between 4.5 and 8.6, the largest differences being found in the lobar bronchi. Sex-based differences were minor in the case of bifurcation angles (e.g., average main bifurcation angle: 93.04 ± 9.58° vs. 91.03 ± 9.81° for men and women, respectively), but large intersubject variability was found irrespective of sex (e.g., range of main bifurcation angle: 65.04°-122.01° vs. 69.46°-113.94° for men and women, respectively). Bronchial segments were shorter by ∼5%-20% in women relative to men, the largest differences being located in the upper lobes. False discovery rate analysis revealed statistically significant associations among morphometric measures of the right lung in women (but not in men), suggesting two phenotypes among women that we attribute to the smaller female thoracic volume.NEW & NOTEWORTHY We found significant sex-based morphometric differences in the central airways of healthy men and women that were only mildly attenuated in subsets matched for lung volume. Lumen areas were significantly larger in men (∼30%-50%). Large variability (∼75%-87%) in airway bifurcation angles (60°-122°) was found irrespective of sex. The branching pattern of the right main and right upper bronchi in women (but not in men) follows two phenotypes modulated by lung volume.
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Affiliation(s)
- Simoni Christou
- Computational Sciences Laboratory (UCY-CompSci), Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia, Cyprus
| | - Thanasis Chatziathanasiou
- Computational Sciences Laboratory (UCY-CompSci), Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia, Cyprus
| | | | - Pantelis Koullapis
- Computational Sciences Laboratory (UCY-CompSci), Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia, Cyprus
| | - Fotos Stylianou
- Computational Sciences Laboratory (UCY-CompSci), Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia, Cyprus
| | - Josué Sznitman
- Department of Biomedical Engineering, Technion-Israel Institute of Technology, Haifa, Israel
| | - Haiwei Henry Guo
- Department of Radiology, Stanford University School of Medicine, Stanford, California
| | - Stavros C Kassinos
- Computational Sciences Laboratory (UCY-CompSci), Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia, Cyprus
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Shachar-Berman L, Bhardwaj S, Ostrovski Y, Das P, Koullapis P, Kassinos S, Sznitman J. In Silico Optimization of Fiber-Shaped Aerosols in Inhalation Therapy for Augmented Targeting and Deposition across the Respiratory Tract. Pharmaceutics 2020; 12:E230. [PMID: 32151016 PMCID: PMC7150950 DOI: 10.3390/pharmaceutics12030230] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Revised: 03/02/2020] [Accepted: 03/03/2020] [Indexed: 11/25/2022] Open
Abstract
Motivated by a desire to uncover new opportunities for designing the size and shape of fiber-shaped aerosols towards improved pulmonary drug delivery deposition outcomes, we explore the transport and deposition characteristics of fibers under physiologically inspired inhalation conditions in silico, mimicking a dry powder inhaler (DPI) maneuver in adult lung models. Here, using computational fluid dynamics (CFD) simulations, we resolve the transient translational and rotational motion of inhaled micron-sized ellipsoid particles under the influence of aerodynamic (i.e., drag, lift) and gravitational forces in a respiratory tract model spanning the first seven bifurcating generations (i.e., from the mouth to upper airways), coupled to a more distal airway model representing nine generations of the mid-bronchial tree. Aerosol deposition efficiencies are quantified as a function of the equivalent diameter (dp) and geometrical aspect ratio (AR), and these are compared to outcomes with traditional spherical particles of equivalent mass. Our results help elucidate how deposition patterns are intimately coupled to dp and AR, whereby high AR fibers in the narrow range of dp = 6-7 µm yield the highest deposition efficiency for targeting the upper- and mid-bronchi, whereas fibers in the range of dp= 4-6 µm are anticipated to cross through the conducting regions and reach the deeper lung regions. Our efforts underscore previously uncovered opportunities to design the shape and size of fiber-like aerosols towards targeted pulmonary drug delivery with increased deposition efficiencies, in particular by leveraging their large payloads for deep lung deposition.
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Affiliation(s)
- Lihi Shachar-Berman
- Department of Biomedical Engineering, Technion—Israel Institute of Technology, Haifa 3200003, Israel; (L.S.-B.); (S.B.); (Y.O.)
| | - Saurabh Bhardwaj
- Department of Biomedical Engineering, Technion—Israel Institute of Technology, Haifa 3200003, Israel; (L.S.-B.); (S.B.); (Y.O.)
| | - Yan Ostrovski
- Department of Biomedical Engineering, Technion—Israel Institute of Technology, Haifa 3200003, Israel; (L.S.-B.); (S.B.); (Y.O.)
| | - Prashant Das
- Department of Mechanical Engineering, University of Alberta, Edmonton, AB T6G 2R3, Canada;
| | - Pantelis Koullapis
- Computational Sciences Laboratory (UCY-CompSci), Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia 1678, Cyprus; (P.K.); (S.K.)
| | - Stavros Kassinos
- Computational Sciences Laboratory (UCY-CompSci), Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia 1678, Cyprus; (P.K.); (S.K.)
| | - Josué Sznitman
- Department of Biomedical Engineering, Technion—Israel Institute of Technology, Haifa 3200003, Israel; (L.S.-B.); (S.B.); (Y.O.)
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Janke T, Koullapis P, Kassinos SC, Bauer K. PIV measurements of the SimInhale benchmark case. Eur J Pharm Sci 2019; 133:183-189. [PMID: 30940542 DOI: 10.1016/j.ejps.2019.03.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 02/26/2019] [Accepted: 03/27/2019] [Indexed: 11/15/2022]
Abstract
Particle Image Velocimetry (PIV) measurements with the aim of providing experimental data for the SimInhale benchmark case are presented within this work. We, therefore, present a refractive index matched, transparent model of the benchmark geometry, in which the velocity and turbulent kinetic energy fields are examined at flow rates comparable to 15, 30 and 60 L/min (Re ≈ 1000-4500) in air. Furthermore, these results are compared with Large Eddy Simulations (LES). The results reveal a Reynolds number independence of the qualitative velocity field in the range covered within this work. Good agreement is found between the PIV and LES data, with a slight over-prediction of turbulent kinetic energies by the simulations. The obtained experimental data will be part of a common, publicly accessible ERCOFTAC database along with additional results published recently.
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Affiliation(s)
- T Janke
- Institute of Mechanics and Fluid Dynamics, TU Bergakademie Freiberg, Freiberg, Germany.
| | - P Koullapis
- Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia, Cyprus
| | - S C Kassinos
- Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia, Cyprus
| | - K Bauer
- Institute of Mechanics and Fluid Dynamics, TU Bergakademie Freiberg, Freiberg, Germany
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Koullapis P, Kassinos SC, Muela J, Perez-Segarra C, Rigola J, Lehmkuhl O, Cui Y, Sommerfeld M, Elcner J, Jicha M, Saveljic I, Filipovic N, Lizal F, Nicolaou L. Regional aerosol deposition in the human airways: The SimInhale benchmark case and a critical assessment of in silico methods. Eur J Pharm Sci 2017; 113:77-94. [PMID: 28890203 DOI: 10.1016/j.ejps.2017.09.003] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 09/01/2017] [Accepted: 09/04/2017] [Indexed: 10/18/2022]
Abstract
Regional deposition effects are important in the pulmonary delivery of drugs intended for the topical treatment of respiratory ailments. They also play a critical role in the systemic delivery of drugs with limited lung bioavailability. In recent years, significant improvements in the quality of pulmonary imaging have taken place, however the resolution of current imaging modalities remains inadequate for quantifying regional deposition. Computational Fluid-Particle Dynamics (CFPD) can fill this gap by providing detailed information about regional deposition in the extrathoracic and conducting airways. It is therefore not surprising that the last 15years have seen an exponential growth in the application of CFPD methods in this area. Survey of the recent literature however, reveals a wide variability in the range of modelling approaches used and in the assumptions made about important physical processes taking place during aerosol inhalation. The purpose of this work is to provide a concise critical review of the computational approaches used to date, and to present a benchmark case for validation of future studies in the upper airways. In the spirit of providing the wider community with a reference for quality assurance of CFPD studies, in vitro deposition measurements have been conducted in a human-based model of the upper airways, and several groups within MP1404 SimInhale have computed the same case using a variety of simulation and discretization approaches. Here, we report the results of this collaborative effort and provide a critical discussion of the performance of the various simulation methods. The benchmark case, in vitro deposition data and in silico results will be published online and made available to the wider community. Particle image velocimetry measurements of the flow, as well as additional numerical results from the community, will be appended to the online database as they become available in the future.
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Affiliation(s)
- P Koullapis
- Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia, Cyprus
| | - S C Kassinos
- Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia, Cyprus
| | - J Muela
- Heat and Mass Transfer Technological Centre, Universitat Politècnica de Catalunya, Terrassa, Spain
| | - C Perez-Segarra
- Heat and Mass Transfer Technological Centre, Universitat Politècnica de Catalunya, Terrassa, Spain
| | - J Rigola
- Heat and Mass Transfer Technological Centre, Universitat Politècnica de Catalunya, Terrassa, Spain
| | - O Lehmkuhl
- Barcelona Supercomputing Center, Barcelona, Spain
| | - Y Cui
- Chair of Applied Mechanics, Friedrich-Alexander University Erlangen-Nuremberg, Germany
| | - M Sommerfeld
- Institute of Process Engineering, Otto von Guericke-University Magdeburg, Halle, Germany
| | - J Elcner
- Faculty of Mechanical Engineering, Brno University of Technology, Brno, Czech Republic
| | - M Jicha
- Faculty of Mechanical Engineering, Brno University of Technology, Brno, Czech Republic
| | - I Saveljic
- Faculty of Engineering, University of Kragujevac, Kragujevac, Serbia
| | - N Filipovic
- Faculty of Engineering, University of Kragujevac, Kragujevac, Serbia
| | - F Lizal
- Faculty of Mechanical Engineering, Brno University of Technology, Brno, Czech Republic
| | - L Nicolaou
- Department of Mechanical Engineering, Imperial College London, London, UK.
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