Direct numerical and large eddy simulations of turbulent flows through concentric annuli

Abstract

Turbulent concentric annular pipe flows are important in various engineering applications such as a heat exchanger and gas-cooled nuclear reactor. It is noted that fully developed flow through concentric annuli has asymmetric distributions of mean quantities unlike those of plane channel flow. The chapter illustrates direct numerical simulation (DNS) and large eddy simulation (LES) for turbulent concentric annular pipe flows with several radius ratios. It examines the mean turbulent quantities and budgets for the Reynolds stress. It is noted that in the inner region, the mean velocity shifts downward from the log law and the normal stresses decrease as the radius ratio decreases. The production terms of the Reynolds stress near the inner wall become smaller than those near the outer wall, and the pressure-strain term of the shear stress in the inner region is also suppressed. In context to the present LES, it is noted that a one-equation-type subgrid scale (SGS) model is used to simulate high-Reynolds number annular pipe flows.