Document Type : Scientific extension


1 Ph.D. Student. Department of Aerospace Engineering, Sharif University of Technology, Tehran, Iran.

2 Professor. Department of Aerospace Engineering, Sharif University of Technology,Tehran, Iran.


The sudden spread of Covid-19 in the world has attracted everyone's attention. In addition, due to the unknown and lack of definitive treatment methods, the World Health Organization and other medical institutions recommend non-pharmacological solutions to control the virus. In this regard, one of the proposed methods is to use masks during this global epidemic as a tool to control the spread of respiratory droplets. Therefore, in this paper, we first examine respiratory events such as breathing, talking, sneezing, and coughing from an engineering perspective and their role in the spread of the virus. In addition, with the help of numerical fluid mechanics, the formation of respiratory droplets and their function in the transmission of infectious respiratory diseases have been studied. Then, the necessity of using a mask and its role in reducing the transmission of the virus is discussed.


Main Subjects

[1] Yao, H., Xiangyun, L., Chen, Q., Xu, K., Chen, Y., Cheng, L., Liu, F., Wu, Z., Wu, H., Jin, C., Zheng, M., Wu, N., Jiang, C., and Li, L., “Patient-Derived Mutations Impact Pathogenicity of SARS-CoV-2”, CELL-D-20-01124, 2020.
 [2] Faranda, D., Castillo, I.P., Hulme, O., Jézéquel, A., Lamb, J., and Thompson, E., “Asymptotic Estimates of SARS-CoV-2 Infection Counts and Their Sensitivity to Stochastic Perturbation”, Chaos an Interdiscip. J. Nonlinear Sci., Vol. 30, No. 5, p. 51107, 2020.
 [3] Mittal, R., “The COVID-19 Airborne Transmission (CAT) Inequality: A Simple Mathematical Framework for Estimating Airborne Transmission of COVID-19”, arXiv Prepr. arXiv2008.00973, 2020.
 [4] Goel, S., Hawi, S., Goel, G., Thakur, V.K., Pearce, O., Hoskins, C., Hussain, T., Agrawal, A., Upadhyaya, H., Cross, G. and Barber, A., “Resilient and Agile Engineering Solutions to Address Societal Challenges such as Coronavirus Pandemic”, Mater. Today Chem., Vol. 17, p. 100300, 2020.
 [5] van Doremalen, N., Bushmaker, T., Morris, D.H., Holbrook, M.G., Gamble, A., Williamson, B.N., Tamin, A., Harcourt, J.L., Thornburg, N.J., Gerber, S.I., Lloyd-Smith, J.O., de Wit, E., and Munster, V.J., “Aerosol and Surface Stability of SARS-CoV2 as Compared with SARS-CoV-1”, N. Engl. J. Med., Vol. 382, No. 16, pp. 1564–1567, 2020.
 [6] Booth, T.F., Kournikakis, B., Bastien, N., Ho, J., Kobasa, D., Stadnyk, L., Li, Y., Spence, M., Paton, S., and Henry, B., “Detection of Airborne Severe Acute Respiratory Syndrome (SARS) Coronavirus and Environmental Contamination in SARS Outbreak Units”, J. Infect. Dis., Vol. 191, No. 9, pp. 1472–1477, 2005.
 [7] Asadi, S., Wexler, A.S., Cappa, C.D., Barreda, S., Bouvier, N.M., and Ristenpart, W.D., “The Coronavirus Pandemic and Aerosols: Does COVID19 Transmit via Expiratory Particles?”, Sci. Rep., Vol. 9, No.1, pp. 2348-2368, 2019.
 [8] Ruiyun, L., Sen, P., Chen, B., Song, Y., Zhang, T., Yang, W., Shaman, J., “Substantial Undocumented Infection Facilitates the Rapid Dissemination of Novel Coronavirus (SARS-CoV-2)”, Science, Vol. 368, No. 6490, pp. 489–493, 2020.
 [9] Yan, J., Grantham, M., Pantelic, J., De Mesquita, P.J.B., Albert, B., Liu, F., Ehrman, S., and Milton, D.K., “Infectious Virus in Exhaled Breath of Symptomatic Seasonal Influenza Cases from a College Community”, Proc. Natl. Acad. Sci., Vol. 115, No. 5, pp. 1081–1086, 2018.
 [10]Verma, S., Dhanak, M., and Frankenfield, J., “Visualizing the Effectiveness of Face Masks in Obstructing Respiratory Jets”, Phys. Fluids, Vol. 32, No. 6, p. 61708, 2020.
 [11]Asadi, S., Wexler, A.S., Cappa, C.D., Barreda, S.; Bouvier, N.M., and Ristenpart, W.D., “Aerosol Emission and Superemission During Human Speech Increase with Voice Loudness”, Sci. Rep., Vol. 9, No. 1, pp. 1–10, 2019.
[12]Drossinos, I. and Stilianakis, N., “What Aerosol Physics Tells Us about Airborne Pathogen Transmission”, Aerosol Science and Technology, Vol. 54, No. 6, pp. 639-643, 2020.
 [13]Guo, Y., Wei, J., Ou, C., Liu, L., Sadrizadeh, S., Jin, T., Tang, L., Zhang, Y., and Li, Y., “Deposition of Droplets from the Trachea or Bronchus in the Respiratory Tract during Exhalation: A Steady-State Numerical Investigation”, Aerosol Sci. Technol., Vol. 54, No. 8, pp. 869– 879, 2020.
 [14]Cui, X., Wu, W., and Ge, H., “Investigation of Airflow Field in the Upper Airway Under Unsteady Respiration Pattern Using Large Eddy Simulation Method”, Respir. Physiol. Neurobiol., p. 103468, 2020.
[15]Feng, S., Shen, C., Xia, N., Song, W., Fan, M., and Cowling, B.J., “Rational Use of Face Masks in the COVID-19 Pandemic”, Lancet Respir. Med., Vol. 8, No. 5, pp. 434–436, 2020.
 [16]Kumar, V., Nallamothu, S., Shrivastava, S., Jadeja, H., Nakod, P., Andrade, P., Doshi, P., and Kumaraswamy, G., “On the Utility of Cloth Facemasks for Controlling Ejecta During Respiratory Events”, arXiv Prepr. arXiv2005.03444, 2020.
 [17]Dbouk, T. and Drikakis, D., “On Respiratory Droplets and Face Masks”, Phys. Fluids, Vol. 32, No. 6, p. 63303, 2020.
 [18]Cummins, C.P., Ajayi, O.J., Mehendale, F.V., Gabl, R., and Viola, I.M., “The Dispersion of Spherical Droplets in Source--Sink Flows and Their Relevance to The COVID-19 Pandemic”, Phys. Fluids, Vol. 32, No. 8, p. 83302, 2020.
 [19]Bourouiba, L., Dehandschoewercker, E., and Bush, J.W., “Violent Expiratory Events: On Coughing and Sneezing”, J. Fluid Mech., Vol. 745, pp. 537–563, 2014.
[20]Weiss, P., Giddey, V., Meyer, D.W., and Jenny, P., “Evaporating Droplets in Shear Turbulence”, Phys. Fluids, Vol. 32, No. 7, p. 73305, 2020.
 [21]Busco, G., Yang, S.R., Seo, J., and Hassan, Y.A., “Sneezing and Asymptomatic Virus Transmission”, Phys. Fluids, Vol. 32, No. 7, p. 73309, 2020.
 [22]Diwan, S.S., Ravichandran, S., Govindarajan, R. and Narasimha, R. “Understanding Transmission Dynamics of COVID-19-Type Infections by Direct Numerical Simulations of Cough/Sneeze Flows”, Trans. Indian Natl. Acad. Eng., Vol. 5, No. 39, pp. 1-7, 2020.
[23]Dudalski, N., Mohamed, A., Mubareka, S., Bi, R., Zhang, C., and Savory, E., “Experimental Investigation of Far-Field Human Cough Airflows from Healthy and Influenza-infected Subjects”, Indoor Air, Vol. 30, No. 5, 2020.
[24]Abkarian, M., Mendez, S., Xue, N., Yang, F., and Stone, H.A., “Puff Trains in Speaking Produce Long-Range Turbulent Jet-Like Transport Potentially Relevant to Asymptomatic Spreading of Viruses”, arXiv Prepr. arXiv2006.10671, 2020.
 [25]Bourouiba, L., “Turbulent Gas Clouds and Respiratory Pathogen Emissions: Potential Implications for Reducing Transmission of COVID19”, JAMA - J. Am. Med. Assoc., Vol. 323, No. 18, pp. 1837–1838, 2020.
[26]Guzman, M.I., “Bioaerosol Size Effect in COVID19 Transmission”, Int. J. Health Plann. Mgmt., Vol. 2020, pp. 1-7, 2020.
 [27]Duguid, J., “The Size and the Duration of Aircarriage of Respiratory Droplets and DropletNuclei”, Epidemiol. Infect., Vol. 44, No. 6, pp. 471– 479, 1946.
[28]Gupta, J.K., Lin, C.-H., and Chen, Q., “Characterizing Exhaled Airflow from Breathing and Talking”, Indoor Air, Vol. 20, No. 1, pp. 31–39, 2010.
[29]Hansen, B. and Mygind, N., “How Often Do Normal Persons Sneeze and Blow the Nose?”, Rhinology, Vol. 40, No. 1, pp. 10–12, 2002.
 [30]Wei, J. and Li, Y., “Enhanced Spread of Expiratory Droplets by Turbulence in a Cough Jet”, Build. Environ., Vol. 93, No. P2, pp. 86–96, 2015.
[31]Parienta, D., Morawska, L., Johnson, G., Ristovski, Z., Hargreaves, M., Mengersen, K., Corbett, S., Chao, C., Li, Y., and Katoshevski, D., “Theoretical Analysis of the Motion and Evaporation of Exhaled Respiratory Droplets of Mixed Composition”, J. Aerosol Sci., Vol. 42, No. 1, pp. 1–10, 2011.
 [32]Chen, C. and Zhao, B., “Some Questions on Dispersion of Human Exhaled Droplets in Ventilation Room: Answers from Numerical Investigation”, Indoor Air, Vol. 20, No. 2, pp. 95– 111, 2010.
[33]Moriarty, J.A. and Grotberg, J., “Flow-induced Instabilities of a Mucus-serous Bilayer”, J. Fluid Mech., Vol. 397, pp. 1–22, 1999.
 [34]Malashenko, A., Tsuda, A., and Haber, S., “Propagation and Breakup of Liquid Menisci and Aerosol Generation in Small Airways”, J. Aerosol Med. Pulm. Drug Deliv., Vol. 22, No. 4, pp. 341– 353, 2009.
[35]Joseph, D.D., Beavers, G.S., and Funada, T., “Rayleigh-Taylor Instability of Viscoelastic Drops at High Weber Numbers”, J. Fluid Mech., Vol. 453, pp. 109–132, 2002.
 [36]Kataoka, I., Ishii, M., and Mishima, K., “Generation and Size Distribution of Droplet in Annular Twophase Flow”, J. Fluids Eng., Vol. 105, No. 2, 1983.
 [37]Romano, F., Fujioka, H., Muradoglu, M., and Grotberg, J., “Liquid Plug Formation in an Airway Closure Model”, Phys. Rev. Fluids, Vol. 4, No. 9, p. 93103, 2019.
[38]Morawska, L., “Droplet Fate in Indoor Environments, or Can We Prevent the Spread of Infection?”, Indoor Air, Vol. 16, No. 5, pp. 335– 347, 2006.
 [39]Renzi, E. and Clarke, A., “Life of a Droplet: Buoyant Vortex Dynamics Drives the Fate of Microparticle Expiratory Ejecta”, Physics of Fluids, Vol. 32, No. 12, 2020.
 [40]Wei, J. and Li, Y., “Airborne Spread of Infectious Agents in the Indoor Environment”, Am. J. Infect. Control, Vol. 44, No. 9, pp. S102–S108, 2016.
[41]Chaudhuri, S., Basu, S., Kabi, P., Unni, V.R., and Saha, A., “Modeling the Role of Respiratory Droplets in Covid-19 Type Pandemics”, Phys. Fluids, Vol. 32, No. 6, p. 63309, 2020.
 [42]Mittal, R., Ni, R., and Seo, J.-H., “The Flow Physics of COVID-19”, J. Fluid Mech., Vol. 894, 2020.
[43]Liu, L., Li, Y., Nielsen, P.V. Wei, J., and Jensen, R.L., “Short-range Airborne Transmission of Expiratory Droplets Between Two People”, Indoor Air, Vol. 27, No. 2, pp. 452–462, 2017.
 [44]Ma, Y., Zhao, Y., Liu, J., He, X., Wang, B., Fu, S., Yan, J., Niu, J., Zhou, J., and Luo, B., “Effects of Temperature Variation and Humidity on the Death of COVID-19 in Wuhan, China”, Sci. Total Environ., p. 138226, 2020.
 [45]Verreault, D., Moineau, S., and Duchaine, C., “Methods for Sampling of Airborne Viruses”, Microbiol. Mol. Biol. Rev., Vol. 72, No. 3, pp. 413– 444, 2008.
 [46]Dbouk, T. and Drikakis, D., “On Coughing and Airborne Droplet Transmission to Humans”, Phys. Fluids, Vol. 32, No. 5, p. 53310, 2020.
 [47]Feng, Y., Marchal, T., Sperry, T., and Yi, H., “Influence of Wind and Relative Humidity on the Social Distancing Effectiveness to Prevent COVID19 Airborne Transmission: A Numerical Study”, J. Aerosol Sci., p. 105585, 2020.
 [48]Berrouk, A.S., Lai, A.C.K., Cheung, A.C.T., and Wong, S.L., “Experimental Measurements and Large Eddy Simulation of Expiratory Droplet Dispersion in a Mechanically Ventilated Enclosure with Thermal Effects”, Build. Environ., Vol. 45, No. 2, pp. 371–379, 2010.
[49]Peng, S., Chen, Q., and Liu, E., “The Role of Computational Fluid Dynamics Tools on Investigation of Pathogen Transmission: Prevention and Control”, Sci. Total Environ., Vol. 746, p. 142090, 2020.
[50]Liang, M., Gao, L., Cheng, C., Zhou, Q., Uy, J.P., Heiner, K., and Sun, C., “Efficacy of Face Mask in Preventing Respiratory Virus Transmission: A Systematic Review and Meta-Analysis”, Travel Med. Infect. Dis., Vol. 36, p. 101751, 2020.
 [51]Eikenberry, S.E., Mancuso, M., Iboi, E., Phan, T., Eikenberry, K., Kuang, Y., Kostelich, E., and Gumel, A.B. “To Mask or Not to Mask: Modeling the Potential for Face Mask Use by the General Public to Curtail the COVID-19 Pandemic”, Infect. Dis. Model., Vol. 5, pp. 293–308, 2020.
[52]Schwartz, K.L., Murti, M., Finkelstein, M., Leis, J.A., Fitzgerald-Husek, A., Bourns, L., Meghani, H., Saunders, A., Allen, V., and Yaffe, B., “Lack of COVID-19 Transmission on an International Flight”, Cmaj, Vol. 192, No. 15, p. E410, 2020.
 [53]Cheng, V.C.-C., Wong, S.-C., Chuang, V.W.-M., So, S.Y.-C., Chen, J.H.-K., Sridhar, S., To, K.K.-W., Chan, J.F.-W., Hung, I.F.-N., Ho, P.-L., and Yuen, K.-Y., “The Role of Community-Wide Wearing of Face Mask for Control of Coronavirus Disease 2019 (COVID-19) Epidemic Due to Sars-Cov-2”, J. Infect., Vol. 81, No. 1, pp. 107–114, 2020.
[54]Li, Y., Wong, T., Chung, J., Guo, Y.P., Hu, J.Y., Guan, Y.T., Yao, L., Song, Q.W., and Newton, E., “In Vivo Protective Performance of n95 Respirator and Surgical Facemask”, Am. J. Ind. Med., Vol. 49, No. 12, pp. 1056–1065, 2006.
 [55]Ahmed, J., Harker, A., and Edirisinghe, M., “Covid19: Facemasks, Healthcare Policies and Risk Factors in the Crucial Initial Months of a Global Pandemic”, Med. Devices Sensors, Vol. 3, No. 1, pp. 1-18, 2020.
[56]Wu, H.L., Huang, J., Zhang, C.J.P., He, Z., and Ming, W.K., “Facemask Shortage and the Novel Coronavirus Disease (COVID-19) Outbreak: Reflections on Public Health Measures”, EClinicalMedicine, Vol. 21, pp. 1-20, 2020.
 [57]Amendola, L., Saurini, M.T., Di Girolamo, F., and Arduini, F., “A Rapid Screening Method for Testing the Efficiency of Masks in Breaking Down Aerosols”, Microchem. J., Vol. 157, p. 104928, 2020.
[58]Abd-Elsayed, A. and Karri, J. “Utility of Substandard Face Mask Options for Health Care Workers During the COVID-19 Pandemic”, Anesth. Analg., Vol. 131, No. 1, pp. 4-6, 2020.
 [59]Neupane, B.B., Mainali, S., Sharma, A., and Giri, B., “Optical Microscopic Study of Surface Morphology and Filtering Efficiency of Face Masks”, PeerJ, Vol. 2019, No. 6, pp. 1–14, 2019.
 [60]Fischer, E.P., Fischer, M.C., Grass, D., Henrion, I., Warren, W.S., and Westman, E., “Low-cost Measurement of Face Mask Efficacy for Filtering Expelled Droplets During Speech”, Sci. Adv., Vol. 6, No. 36, pp. 2–7, 2020.
 [61]Yi, L., Fengzhi, L., and Qingyong, Z., “Numerical Simulation of Virus Diffusion in Facemask During Breathing Cycles”, Int. J. Heat Mass Transf., Vol. 48, No. 19–20, pp. 4229–4242, 2005.
 [62]Li, Y., Guo, Y.P., Wong, K.C.T., Chung, W.Y.J., Gohel, M.D.I., and Leung, H.M.P., “Transmission of Communicable Respiratory Infections and Facemasks”, J. Multidiscip. Healthc., Vol. 1, pp. 17–27, 2008.
[63]Kumar, S. and Lee, H.P., “The Perspective of Fluid Flow Behavior of Respiratory Droplets and Aerosols Through the Facemasks in Context of SARS-CoV2”, Physics of Fluids, Vol. 32, pp. 111301, 2020.
[64]Przekwas, A. and Chen, Z., “Washing Hands and the Face May Reduce COVID-19 Infection”, Med. Hypotheses, Vol. 144, p. 110261, 2020.
[65]Chandrasekaran, B. and Fernandes, S., “‘Exercise with Facemask; Are We Handling a Devil’s Sword?’ –A Physiological Hypothesis”, Med. Hypotheses, Vol. 144, p. 110002, 2020.