Distinctive Features of Propagation of a Turbulent Pulsed Gas-Droplet Eddy Cloud

Abstract

We present the results of the numerical modeling of the formation and motion of a blown solitary pulsed turbulent gas-droplet jet under the conditions approximately corresponding to human cough. The calculations are performed for the pulse duration t = 0.6 s and the greatest velocity of the gas phase of 20 m/s at the mass fraction of droplets M_L1 = 1%. The drop phase in the exit section is monodisperse, while the initial dimension of particles in the calculations varied in the range D₁ = 5‒30 μm. Two zones of elevated vorticity are formed within the cloud in the initial period of motion. They are situated in the mixing layer and in the region of deceleration of two-phase pulsed jet. The greatest levels of the longitudinal velocity and the kinetic energy of turbulence are attained in the interval of pulse blow-on. At the subsequent moments of time the turbulence velocity and level monotonically decrease. The vortex cloud produced by the solitary pulse exists for a fairly long time (t ≈ 4 s) and has a time to penetrate into the surrounding space at a distance greater than 3 m.