Large-eddy simulation of a pure thermal plume under rotating conditions

Abstract

The spatial development of turbulent thermal plumes under rotating conditions of the heat source has been investigated using large-eddy simulations. In order to analyze the rotation effect of the heat source in an otherwise quiescent environment, a range of rotation frequencies is considered in an intermediary Rossby number regime in which inertial and Coriolis forces strongly interact. Above a threshold Rossby number of about 1.82, the influence of heat source rotation is insignificant. Below the threshold heat source, rotation has a significant influence. In the region close to the heat source there is a strong interaction region between the plume development and heat source rotation. Radial transport across the plume is amplified and a mixing process through shear-layer development enhances engulfment of ambient fluid into the thermal plume. Farther above the plume the direct effect of source rotation decays and becomes insignificant. The plume continues to be wider, but this is due to the swirling effects imparted to the base of the plume at the heat source. Thus, after an initial enhancement of entrainment, the resulting flow field behaves as would a nonrotating plume driven by buoyancy, convection, and turbulent mixing.