Three-dimensional aspects of the organized motion in a turbulent boundary layer

Abstract

Velocity data have been obtained in a turbulent flat plate boundary layer with a rake of eight X-probes, first normal to the wall and then parallel at several heights. Identical detection procedures are applied to the lines of intersection of the planes of data, and sectional streamlines and vorticity contours are calculated throughout the planes from the conditioned velocities, giving different cuts through the same structures. Near the wall the revised, modified u-level approach is used to detect bursts. Further from the wall the WAG method is used to detect highly three-dimensional large structures, which appear as a series of spanwise vortices in the plane normal to the wall and as smaller, counter-rotating regions in planes parallel to the wall. Additional criteria are used to show that perfect symmetry is artificial in the latter planes, but other conclusions drawn from symmetrical results are not invalidated. A brief comparison is made with results in the far-wake of a circular cylinder.