Laminar separating flow over backsteps and cavities. II - Cavities

Data on flow over backsteps and cavities for the laminar case are very scant. The present paper reports the results of an experimental investigation carried out at a wind speed of 1.8 m/s past eight rectangular cavities of depth 0.625, 1.25, and 2.5 cm and depth-to-width ratios h/b in the range 0.035-2.5; the separating boundary layer in all cases was laminar and was of thickness 1.4 cm. The Reynolds numbers, based on the cavity depth, were 662, 1324, and 2648. Results of smoke flow visualization and static pressure and hot-wire measurements show that as in the case of turbulent flows, cavities can be classified as closed, shallow open, and open depending on the range of the value of the ratio h/b. The mean velocity profiles in the free shear region show self-similarity and the flow in the recirculating region of the shallow open cavity appears to have the character of a wall jet in the reverse direction superimposed on a forward-moving free shear layer. Typical development of streamwise mean velocity profile and intensity of fluctuations are also presented. h p Reb Re ^ u' U Um Ur Urm