Separation and wake of pulsating laminar flow

Abstract
This is an experimental study of laminar pulsating flow that passes through separation and is led to a separated region. Detailed information is obtained on all interconnected regions, namely, the approaching attached laminar boundary layer, the immediate neighbourhood of separation, the separated shear layer, the large-scale vortical region of the wake and the outer inviscid flow. The approaching flow is pulsated with frequencies that include the natural frequencies of the wake. Flow visualizations are contrasted with instantaneous and averaged digital data obtained via laser-Doppler velocimetry and hot-wire anemometry. The interaction of the disturbing and natural frequencies is studied. Results are com pared with recent theoretical advances. It is found that the amplitude of the imposed disturbance grows sharply in the neighbourhood of separation.