Laminar separating flow over backsteps and cavities. I - Backsteps

Abstract

Although significant data on flow over backward facing steps and cavities in turbulent flow are available, the corresponding data for the laminar flow are rather scant. The present work reports the results of an experimental investigation carried out at a wind speed of 1.8 m/s over three backward facing steps 0.625,1.25, and 2.5 cm high; the separating boundary layer in all cases was laminar and was 1.4 cm thick. Data obtained through smoke flow visualization and static pressure and hot wire measurements are divided into two categories: category A—variation of the reattachment length with Reynolds number in the range 100-12,500, and category B—general pattern of flow between the point of separation and that of reattachment. The data in the latter category include 1) pressure profiles on the step surfaces, 2) typical development of streamwise mean velocity profile and intensity of fluctuations, 3) variation of momentum thickness of the laminar separating shear layer downstream of the steps.