Hydrodynamics of the Mixing Layer Bounding a Separation Zone Using SPIV, Part1: Mean Flow Structure

The shallow mixing layer bounding a separation zone is a prominent but poorly understood hydrodynamic feature. To investigate characteristics of the separated shallow mixing layer generated by a single side obstacle, experimental measurements were obtained by means of high resolution surface particle image velocimetry (SPIV). Results indicate that unlike the free shallow mixing layers and also mixing layers bounding a deep circulation zone, the velocity profiles are self similar just in a short distance downstream of the groyne and also near the reattachment region. Furthermore, growth of the width of the mixing layer with downstream distance shows a two-phase development. The firstphase is exponential until a distance about 3.5L, where L is the abutment length, followed by a second-phase characterized by a linear pattern. The growth rate of the first stage is higher than the second phase.