Direct Numerical Simulation of Concentric Annular Turbulent Flows with Very Thin Inner Rods

Abstract

Turbulent concentric annular pipe flows with several thin inner rods were invistigated by means of the direct numerical simulation (DNS). In the inner region, the mean velocity shifts downward from the logarithmic law and the Reynolds stresses normalized by the inner-wall friction velocity decrease monotonously as the radius ratio decreases. In the budget of the Reynolds stress for the very small radius ratios, the pressure-strain term is restrained near the inner wall. We found that the skewness, flatness, two-point correlation and instantaneous field for very small radius ratios are much different from those for large radius ratios.