图书馆订阅: Guest
TSFP DL Home 旧刊 执委

ROTATING STRATIFIED TURBULENCE WITH VERTICAL AND NON-VERTICAL SHEAR

Frank G. Jacobitz
Mechanical Engineering Program University of San Diego 5998 Alcala Park San Diego, California 92110, USA

Abstract

Direct numerical simulations are performed to investigate the effect of stratification, shear, and rotation, on the evolution of homogeneous turbulence. This study considers uniform vertical stable stratification as well as vertical and non-vertical shear and system rotation. The rotation axis is always normal to the plane of shear and it is therefore parallel or anti-parallel to the mean flow vorticity. Three parameters are used to characterize the flow: the Richardson number Ri = N2/S2, which is the square of the ratio of Brunt-Vaisala frequency N to shear rate S, the rotation ratio f/S, which is the ratio of Coriolis parameter f to shear rate S, and the shear angle θ between the plane of shear and the vertical. An increase of the Richardson number Ri leads to weakened growth of the turbulent kinetic energy K. In the anti-parallel flow configuration, turbulence growth is amplified for rotation ratios between 0 < f/S < 1 and weakened otherwise. For f/S = 0.5 the value of the critical Richardson number Ricr, which distinguishes turbulence growth from decay, exceeds the classical value of a quarter obtained from linear inviscid stability theory. In the parallel flow configuration, the turbulence is weakened by rotation for all values of the rotation ratio f/S. Non-vertical shear generally leads to stronger turbulence growth. This effect is strongest in the anti-parallel flow configuration and weakest in the parallel flow configuration.