Effect of coughing pulsatility on the effectiveness of a surgical mask

It is well established that diseases such as COVID-19 are spread by airborne transmission, as infectious particles are generated in respiratory events like talking and coughing. Although coughing is a multi-pulsed event, the pulsatile nature of coughs on the dispersion of droplets is not well understood. One strategy to reduce disease transmission via expiration is the use of face coverings. In this work, the effectiveness of a surgical mask is studied for single- and double-pulsed coughs. Three cases are considered: a single-pulse (S1), a double-pulse (D1) comprising two S1 pulses and a single-pulse (S2) with the same cough expired volume as D1. Using a custom-built pulsatile coughing simulator, the flow leakage around the mask is quantified via flow visualization and PIV. The flow velocity profiles at the side and top of the mask take the form of a jet and a wall jet, respectively. Preliminary results show that the leakage volume expelled in a D1 event is greater than for S1 and S2. The leakage penetration distance at the side and top of the mask both appear to scale with t^1/2 in the starting jet stage and t^1/4 in the interrupted jet stage.