Study of a lead-bismuth eutectic jet issued into a heated cavity using large eddy simulation

Abstract

Low Prandtl number convection of an axisymmetric turbulent lead-bismuth eutectic (LBE) jet discharged into a heated confined geometry using large eddy simulation is investigated. The Reynolds number based on jet centerline velocity and jet diameter is Re = 44,706. The results demonstrate some features of liquid metal that deviate from those of ordinary fluids. Examples include the differences between fluctuations of temperature and velocity, the distributions of turbulent viscosity and turbulent diffusivity of heat, and the misalignment between the turbulent heat flux vector and the gradient of mean temperature, all of which imply that standard turbulence models may not be suitable for the simulation of such flows. The LBE jet at Pr = 0.03 is compared with a high-pressure water jet at Pr = 0.8 under the same Re and Fr. The centerline decay of the mean velocity for LBE demonstrates the same behavior as that of water, which is governed by a linear variation for the self-preservation region between 1.5D and 8.5D, where D is the diameter of the jet orifice. In contrast, the centerline mean temperature for LBE decreases slower compared with that of water. The difference in temperature results from the high intensity of molecular diffusion in heat transport in LBE, while the momentum transport is mainly by turbulent diffusion in both flows. Self-preserving characteristic of temperature r.m.s (Trms) is observed. The radial profiles of Trms are presented by an axisymmetric curve with a maximum at around 0.7b, where b is the half-value radius of Trms. Good agreement of mean temperature distribution between the simulation results and the experiments are obtained.