Large-eddy simulation of droplet-laden cough jets with a realistic manikin model

Abstract

Three-dimensional computational fluid dynamic (CFD) methods were used to simulate a cough jet that contains droplets. The turbulent cough flow is modelled using large-eddy simulation with a dynamic structure model. An Eulerian–Lagrangian approach was adopted to model the two-phase flows. Droplet breakup, evaporation, dispersion and drag forces were considered in the model. Two different inlet velocity profiles, which are based on constant mouth opening area and variable mouth opening area, were considered in the CFD model. The numerical model was validated by comparing with the available experimental measurements. The results show that the use of the fixed mouth opening area in the geometric model shows the inlet velocity profile of the ‘variable area’ matched better with the experimental data than with the ‘constant area’ inlet velocity profile. Droplet dynamics were analysed with a focus on the droplet penetration and droplet distribution in space during the whole coughing process. The droplet penetration shows two-stage profiles, both of which can be described by logarithmic functions. This is consistent with the analytical results of the simplified drag model. The droplets generated during the mouth opening or closing periods have a higher velocity and longer droplet penetration. With a higher room temperature, the droplet penetration is shorter.