Numerical Simulation of a Round Buoyant Jet in a Counterflow

Abstract

Discharge of pollutants into the receiving water bodies is generally in the form of a turbulent jet or plume, the presence of a counterflow enhances the initial dilution of the jet effluent. To obtain better understanding of jet behaviors in a realistic situation, a round buoyant jet issuing horizontally into a uniform counterflow is simulated at different combinations of densimetric Froude number (F) and jet-to-current velocity ratio (R). A two-phase mixture model simulates this flow and the renormalization group (RNG) k-ɛ model to solve flow turbulence. The inter-phase interactions are described in terms of relative slip velocity between phases. The numerical results of concentration field are in good agreement with W.Y.Lee's experimental observation. The jet features including trajectory of the jet centerline and the decay of centerline concentration are studied. Through the comparison of all cases, this paper also analysis the effect of buoyancy and velocity ratio on jet behaviors. Based on length scale analysis, the article gives the corresponding relationships between the distance and the centerline dilutions. The results indicate that the flow mechanisms before and after the penetration point are quite different.