Cavitation in Large Scale Shear Flows

Abstract

Cavitation phenomena were studied in the shear layer behind a two-dimensional sharp-edged plate. Observations were made under stroboscopic light and by flash photography. The first traces of cavitation appear as a series of narrow long axial “strings” suggesting that the major contributor to cavitation inception is the longitudinal (axial) secondary shear layer eddy structure. In a more developed state the cavitation takes the form of a spanwise large eddy structure but the axial “strings” are still evident. The local cavitation inception indices based on the local velocity and pressure scatter between 1.0 and 1.4 when the water is saturated with dissolved air and vary between 0.8 and 1.2 when the air content is reduced to about 30 percent of saturation. These results are in good agreement with a collection of other measurements behind sharp-edged disks that display a consistent increase of the inception index with the Reynolds number.