Effect of Reynolds number on the topology of the organized motion in a turbulent boundary layer

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Abstract
The influence of Reynolds number on the topology of the organized motion in a turbulent boundary layer is studied with the use of an array of eight ×-probes in the plane of mean shear. Instantaneous sectional streamlines and contours of large-scale approximations to the spanwise vorticity and strain rate suggest that the motion is relatively complicated at all Reynolds numbers. Contours, conditioned on the spatially coherent increase in the velocity fluctuation u, extend to larger distances from the wall at the smaller Reynolds numbers. Reasonable correspondence is found between the location of this increase in the near-wall region and the end of a burst. Associated with this increase is an important contribution to the Reynolds shear stress throughout the layer. This contribution is larger at the smaller Reynolds numbers.