Boundary layer development after a region of three-dimensional separated flow

The development of the boundary layer flow down stream of a region of three-dimensional turbulent separated flow has been investigated using hot-wire anemometry and pulsed-wire anemometry for wall shear stress. The flow, generated by means of a 'v-shaped' separation line, was set up so as to generate a central region of fully three-dimensional flow, bounded on each side by the degenerate case of spanwise-invariant flow, which is closely related to two-dimensional co-planar flow. The flow developing in the central region has fundamentally different features from that after a region of two-dimensional separated flow. A bulge in the boundary layer, generated in the separated flow, has a strong wake-like characteristic that sits very persistently in the outer part of the layer, its shape and relative size changing little in similar to25 reattachment length scales. The Reynolds stresses in this bulge region, driven by the mean velocity gradient of the wake-like flow, are very much larger than the normal levels in the boundary layer or in the developing region downstream of a two-dimensional separation. The inner layer that lies beneath the bulge is subjected to a high level of non-shear-stress-containing motion, the normal stresses being much higher than the shear stress which exhibits a constant level in the inner layer despite much higher levels further out. (C) 2003 Elsevier SAS. All rights reserved.