Large Eddy Simulation of a Three Dimensional Buoyant Jet

Abstract

This study is related to the numerical simulations of a three dimensional buoyant jet. The governing equations of the fluid are solved with the help of a buoyancy-extended large eddy simulation (LES) numerical model. In addition, the dynamic procedure is used to evaluate the Smagorinsky model coefficient. The finite difference formulations of the governing equations are split into three parts related to advection, dispersion and propagation. The advection part is solved by the QUICKEST scheme. The dispersion part is solved by the central difference method and the propagation part is solved implicitly by using the Gauss-Seidel iteration method. The initial turbulence of the buoyant jet from the orifice is accounted for by introducing random disturbances to the flowing parameters. Ensemble averaged relationships for the buoyant jet trajectory; jet sizes and concentration dilution are presented. The salient characteristics of the buoyant jet are captured, including variability among different realizations of the buoyant jet, the development of protuberances, the horseshoe cross sectional shape and the hollow trough along the upper surface of the jet. The protuberance characteristic and the asymmetric shape of the jet from the present study are compared with the results from the conventional κ-ε model. The horseshoe cross sectional shape and the trough or bifurcation characteristics are investigated by studying the inner structures of the flow field. These quantitative relationships and qualitative observations are found to be in good agreement with experimental results from an earlier investigation.