Models of defining the thermo-fluid conditions for various exhalations

The transmission of airborne disease starts when the disease viruses are exhaled from an infected person. The present study developed a set of equations to provide the flow boundary conditions to CFD simulations for the exhalations from coughing, breathing and talking processes. The study conducted measurements on the flow rate, flow direction and area of mouth/nose opening with human subjects. The flow rate variation over time can be defined as a combination of gamma-probability-distribution functions for a cough; sinusoidal function for breathing, and a constant for talking process. The variables required to define these functions can be obtained from the physiological details of a person. The direction of the exhalation jet and the area of mouth/nose opening did not vary during these processes. A mean value to define these parameters as boundary conditions is thus proposed. The developed equations can be combined with appropriate infectious droplet information to predict the spread.