On the use of vortex generators to control cavitation in a backward facing step flow

Cavitation inception was studied for vortex-generator-controlled, backward-facing step flow to reveal the relationship of the modified viscous flow structures and cavitation inception. Comparison with a baseline backward facing step flow was made, and the issues of using vortex generators to control cavitation inception was discussed. Non-cavitating flow fields for both baseline and control cases were measured using particle image velocimetry (PIV) and laser Doppler velocimetry (LDV). Pressure field, which is important to cavitation inception, was simulated using the commercial software FLUENT. Cavitation was achieved in the high expansion ratio (ER = 1.9) test section by operating the flow system at a higher flow rate. Flow visualization of cavitation inception was performed using PIV. The vortex-generator-modified shear layer was found to cavitate earlier than the baseline backward facing step flow. The cavitation zones on the center and side planes of the controlled case appear slightly different. On the center plane, adjacent to the shear layer, the cavitation zone extended to the core region of the separation bubble. The cavitation zone did not appear in the region of high velocity fluctuations. The shear layer strength (ω a)* proved to be a good predictor of cavitation location. While vortex generators can be used to control cavitation, the induced streamwise vortices result in detrimental effects, which outweigh their control benefits.