The effect of environmental conditions on spreading of droplet-laden mist pulsed turbulent jet

This paper presents the results of numerical simulation of the formation and motion of a single pulsed turbulent gas-droplet jet, roughly corresponding to the conditions of a human cough. Predictions of the averaged local turbulent flow structure and droplets distributions are made using the axisymmetric 3D URANS approach and the second-moment closure turbulence model. The simulations were performed for duration of a single cough pulse t = 0.6 s and a maximum gas phase velocity of 20 m/s, with the initial mass fraction of droplets M L 1 = 1–5% and droplet diameter D 1 = 10–100 μm. The highest level of the longitudinal component of the averaged velocity and kinetic energy of turbulence is achieved during the pulse blowing period. Thereafter, a monotonic decrease in velocity and turbulence occurs. The vortex cloud persists for a relatively long time (minimum t ≥ 4 s) and during this time it spreads in the surrounding flooded space to a distance of more than 3 m before the liquid droplets evaporate completely. Maximum expansion of the pulsed two-phase round jet reaches nine-hole diameters. The maximum longitudinal velocity and the kinetic energy of turbulence are reached during the initial phase of the cloud motion at the stage of the jet outflow.