Prediction of passive scalar in a mixing layer using vortex-in-cell and probability density function methods.

Abstract

The transport equation for the probability density function (p.d.f.) of a scalar is applied in conjunction with the vortex-in-cell (VIC) method developed by Abdolhosseini and Milane (1998), to predict the passive scalar field in a two-dimensional spatially growing mixing layer. The VIC method predicts the instantaneous velocity field. Then the turbulent flow characteristics such as mean velocity, the root-mean-square (r.m.s.) longitudinal and lateral velocity fluctuations and the Reynolds shear stress are calculated. The scalar field is represented through the transport equation for the scalar p.d.f. and is solved using the Monte Carlo technique. In the p.d.f. equation, turbulent diffusion is modeled using the gradient transport model, wherein the eddy diffusivity is computed using Boussinesq's postulate and using the Reynolds shear stress and gradient of mean velocity from the VIC solution. The molecular mixing term is closed by a modified Curl model, and the convection term uses the mean velocity from the VIC solution. The computational results were compared with available two-dimensional experimental results. (Abstract shortened by UMI.)