Abstract
Turbulent concentric annular pipe flows with four radius ratios were investigated 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 decrease as the radius ratio α decreases. We found that the high order statistics and instantaneous fields for very small radious ration (α=0.025) are much different from those for α=0.1 and α=0.2.
