On the Mutual Interaction between Wall Boundary Layer and Two-Dimensional Vortical Motion

Abstract

Hydrodynamic interaction reported in this paper was initiated in experiments on two-dimensional vortical motion which was produced in transition of the two-stream mixing layer. The mixing layer was developing non-lineally and the boundary layer on the side wall, which was perpendicular to the mixing layer, was laminar at the origin of the mixing layer. The phenomenon was that the interface between the two boundary layers of high and low streams was at first excited by the vortical motion in a roll-up type. This disturbance was quickly developed at the interface and also was propagated into the boundary layer of high-stream side. The disturbances at the interface and in the high-stream side coincided to form a large and coherent vortical motion of which both tails lay longitudinally in the boundary layer of the high-stream side, and the central part elongated into vortical motion of the mixing layer. This elongated one could be recognized as the “inflow” pointed out by Browand. Both inflows developed from side walls pushed the mixing layer toward its center line. Then the mixing layer in the duct center was skewed to be a partial pairing. Two-dimensional vortical motion was broken down to turbulence after the partial pairing progressed abruptly over the full span of the duct.