Simulations of Respiratory Droplet Spray

As part of the Summer High School Intensive in Next Generation Engineering (SHINE) with the University of Southern California's (USC) Viterbi School of Engineering, this work examines the transmission of the COVID-19 virus through respiratory droplets expelled from an infected individual. Social distancing and face masking protocols have been implemented to reduce the spread of droplets. This study aimed to assess the effectiveness of the recommendations using computational fluid dynamics simulations based upon the ANSYS Fluent Student Edition with two-dimensional axisymmetric simulations. The four most common ways of spreading respiratory droplets, including breathing, talking, coughing, and sneezing, were examined. Before completing the droplet spray simulations, several canonical jet flows were simulated to verify the validity of Fluent's application. Specifically, laminar and turbulent free jets were modeled and compared against experimental data. In addition, standard features of jets such as self-similarity, spreading ratios, and centerline velocity decay were verified from the solutions. Once the computations were validated, simulations were completed for each of the four cases at the six-foot recommended social distancing to determine the droplet concentration reduction. The simulations were run at increasing grid resolution to verify grid and time-step independence. Finally, the simulations were repeated for the case with face masks to assess the additional reduction of droplets reaching the receiver at the recommended distance. At the recommended social distancing with masking, the number of droplets coming into contact with others was reduced to negligible amounts. The simulations showed the recommended protocols are highly effective at reducing the transmission of COVID-19.