DIRECT NUMERICAL SIMULATIONS OF EVAPORATING DROPLET DISPERSION IN FORCED LOW MACH NUMBER TURBULENCE

Dispersion of evaporating droplets in forced low Mach number isotropic turbulence is studied using direct numerical simulation (DNS). The ca rrier phase is treated in the Eulerian frame, the droplets are tracked in the Lagrangian frame, and a (realistic) two-way coupling is consid ered. The results of the simulations are used to investigate the effec ts of the initial droplet time constant, the initial mass loading rati o, the initial droplet temperature, the latent heat of evaporation, th e boiling temperature, and the initial vapor mass fraction on the drop let size, the temperature fields, and the vapor mass fraction. The DNS results indicate that the evaporation rate is nonlinear during the ea rly times. The pdfs of the droplet diameter are skewed towards smaller droplets, however, they may be approximated as Gaussian for small mas s loading ratios. An examination of the mean vapor mass fraction indic ates that the mixture becomes nearly saturated at long times. The evol ution of the fluctuating vapor mass fraction is investigated by consid ering the transport equation for the variance of this quantity. (C) 19 98 Elsevier Science Ltd. All rights. reserved.