低レイノルズ数正方形管内乱流壁面せん断応力とレイノルズ応力

概要

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Turbulence measurements have been performed by using an LDV in a fully developed squareduct flow at low Reynolds number Re〓7000. A local wall shear stress, turbulence intensities and Reynolds shear stresses, -<u'v'>^^^ and -<u'w'>^^^, are presented to discuss the consistency of recently reported low-Reynolds-number DNS data(Gavrilakis 1992;Huser and Biringen 1993)with the experimental results. In contrast to high-Reynolds-number cases, the spanwise (z-directional)profile of a wall shear stress has two peaks in 0≤z/H≤0.5, one of which is located at a wall bisector z/H=0.5 and another of which is around z/H=0.1, and the maximum appears at the wall bisector. Such low-Reynolds-number behaviour has also been observed for the wall stress in the DNS. However, some of turbulence statistics, in particular turbulence intensities, reported by the DNS study are found to be inconsistent with those of the present experiment. This could suggest the possibility that DNS fails in predicting proper statistics if the axial extent of a computational domain is not taken to be long enough to capture a large-scale structure in the axial direction.
2000-01-25