Heat transfer in a stably stratified grid-generated flow

Abstract

The evolution of grid-generated turbulence is affected by buoyancy force in a stratified flow, where heat transfer is controlled by turbulent motion and stratification. It is known that the counter-gradient scalar transfer occurs in a turbulent flow with strongly stable stratification. In previous works, the effects of the degree of stratification and the Prandtl (or Schmidt) number on the heat transfer mechanism have been investigated (Lienhard and Van Atta 1990; Yoon and Warhaft 1991; Komori et al. 1994). The results show that the counter gradient transfer is initiated at small scales in high Prandtl number water flows (Komori et al. 1994). However, it remains to be determined experimentally and numerically how small-scale turbulent motion affects the counter-gradient heat transfer in air flow of low Prandtl number. The purpose of the present paper is to investigate the counter-gradient heat transfer in stably stratified air flow.