Cavitation in shear layer of a backward facing step

The backward facing step is used as the baseline geometry in experimental studies on separation and reattachment in turbulent flows. Separated shear flow behind a backward facing wedge can experience cavitation when the local pressure is close to vapor pressure in the shear layer. Current study focuses on quantifying the developing and fully developed cavitation in the shear layer and separation region formed downstream a backward facing step. As the cavitation number is lowered from the point of inception, the shear flow begins to fill with vapor forming into a fully developed/filled cavitation and then, with lower pressure, a super-cavity. The underlying multiphase flow features are examined using time-resolved X-Ray densitometry and high speed videography. The void fraction measurements are used to quantify vapor production, convection and shedding. These measurements reveal the presence of propagating condensation shock-waves associated with partial cavity shedding. In addition, 2-D planar PIV is performed to characterize the turbulent boundary layer upstream of the liquid separation at the step edge.