A Numerical Study on the Turbulent Schmidt Numbers in a Jet in Crossflow

Abstract

This work presents a numerical study on the turbulent Schmidt numbers in jets in crossflow. This study contains two main parts. In the first part the problem of the proper choice of the turbulent Schmidt number in the Reynolds-Averaged Navier-Stokes (RANS) jet in crossflow mixing simulations is outlined. The results of RANS employing the shear-stress transport (SST) model of Menter and its curvature correction modification and different turbulent Schmidt number values are validated against experimental data. The dependence of the “optimal” value of the turbulent Schmidt number on the dynamic RANS model is studied. Furthermore a comparison is made with the large-eddy simulation (LES) results obtained using the WALE (Wall-Adapted Local Eddy Viscosity) model. The accuracy given by LES is superior in comparison to RANS results. This leads to the second part of the current study, in which the time-averaged mean and fluctuating velocity and scalar fields from LES are used for the evaluation of the turbulent viscosities, turbulent scalar diffusivities, and the turbulent Schmidt numbers in a jet in crossflow configuration. The values obtained from the LES data are compared with those given by the RANS modeling. The deviations are discussed and the possible ways for the RANS model improvements are outlined.