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We provide research findings on the physics of aerosol and droplet dispersion relevant to the hypothesized aerosol transmission of SARS-CoV-2 during the current pandemic. We utilize physics-based modeling at different levels of complexity, along with previous literature on coronaviruses, to investigate the possibility of airborne transmission. The previous literature, our 0D-3D simulations by various physics-based models, and theoretical calculations, indicate that the typical size range of speech and cough originated droplets ( ) allows lingering in the air for ) so that they could be inhaled. Consistent with the previous literature, numerical evidence on the rapid drying process of even large droplets, up to sizes , into droplet nuclei/aerosols is provided. Based on the literature and the public media sources, we provide evidence that the individuals, who have been tested positive on COVID-19, could have been exposed to aerosols/droplet nuclei by inhaling them in significant numbers e.g. . By 3D scale-resolving computational fluid dynamics (CFD) simulations, we give various examples on the transport and dilution of aerosols ( ) over distances in generic environments. We study susceptible and infected individuals in generic public places by Monte-Carlo modelling. The developed model takes into account the locally varying aerosol concentration levels which the susceptible accumulate via inhalation. The introduced concept, ’exposure time’ to virus containing aerosols is proposed to complement the traditional ’safety distance’ thinking. We show that the exposure time to inhale aerosols could range from to or even to depending on the situation. The Monte-Carlo simulations, along with the theory, provide clear quantitative insight to the exposure time in different public indoor environments.

His research interests include subgrid-scale models and numerical methods for large-eddy simulation, adaptive mesh refinement, immersed boundary methods, and Lagrangian particle methods.

the publicly released software has only existed since 2000. Since its first release, continued improvements have been made to the software based largely on feedback from its users. Included here are some who made important contributions.At NIST, thanks to Dan Madrzykowski, Doug Walton, Bob Vettori, Dave Stroup, Steve Kerber and Nelson Bryner, who have used FDS and Smokeview as part of several investigations of fire fighter line of duty deaths. As part of these studies, they have provided valuable information on the model's usability and accuracy when compared to large scale measurements made during fire reconstructions.The US Nuclear Regulatory Commission has provided financial support for the maintenance and development of FDS, along with valuable insights into how fire models are used as part of probabilistic risk assessments of nuclear facilities. Special thanks to Mark Salley and Jason Dreisbach of NRC, and Francisco Joglar of SAIC.The Society of Fire Protection Engineers (SFPE) sponsors a training course on the use of FDS and Smokeview. Chris Wood of ArupFire, Dave Sheppard of the US Bureau of Alcohol, Tobacco and Firearms (ATF), and Doug Carpenter of Combustion Science and Engineering developed the materials for the course, along with Morgan Hurley of the SFPE.Prof. David McGill of Seneca College, Ontario, Canada has conducted a remote-learning course on the use of FDS, and he has also maintained a web site that has provided valuable suggestions from users.Thanks to Chris Lautenburger and Carlos Fernandez-Pello for their assistance with the "two-reaction" test case.Thanks to Ian Thomas, Khalid Moinuddin, and Ian Bennetts for their description of and data for the ethanol pan fire example. Prof. Ian Thomas of Victoria University has also presented short courses on the use of FDS in Australia. His students have also performed some validation work on compartment fires.Prof. Charles Fleischmann and his students at the University of Canterbury, New Zealand, have provided valuable assistance in improving the documentation and usability of the model.James White Jr. of the Western Fire Center has provided valuable feedback on how to improve the functionality of the model in the area of forensic science.Paul Hart of Swiss Re, GAP Services, and Pravinray Gandhi of Underwriters Laboratories provided useful suggestions about water droplet transport on solid objects.Finally, on the following pages is a list of individuals and organizations who have volunteered their time and effort to "beta test" FDS and Smokeview prior to its official release. Their contribution is invaluable because there is simply no other way to test all of the various features of the model.

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