Hydrodynamics of horizontal heated buoyant jet in linearly stratified fluids

Abstract

Horizontal buoyant jets in stratified fluids are investigated by employing a computational fluid dynamic model validated by experimental data. The characteristics of time mean flow, turbulence, and entrainment are quantified. We observed that turbulence parameters such as the turbulent kinetic energy, the turbulence dissipation rate, and turbulent viscosity attained their maximum values in the horizontal region. Here, the entrainment coefficient also reaches the maximum due to the instantaneous instability of the flow. The ascent region consists of the acceleration and deceleration stages due to the stratified ambience reversing the sign of buoyancy flux. In the acceleration ascent region, the entrainment coefficient stabilizes around 0.05. In the deceleration stage, the transition of the flow regime from plume- to jet-like regulates the entrainment. At the end of the ascent region, the jet reaches the maximum rise height (Hmax), which can be well predicted by a semiempirical function at a given Richardson number, buoyancy frequency, and Reynolds number. An enhancement of turbulent parameters is observed near the Hmax and could be attributed to overshooting and shearing between the up- and downflow. Analysis of density and velocity profiles shows the heavy fluids on the lower side of the jet core vertically separating from the center fluids, which drifted the velocity profile from a Gauss to a fat-tailed distribution and broke the self-similarity.