Cavitation Dynamics in Wakes Behind Bluff Bodies

Properties of wakes behind bluff bodies such as shedding frequency, vortex spacing, and drag change with the presence of cavitation. As extent of cavitation in the wake increases from inception to an attached super-cavity, wake shedding Strouhal number increases, reaching a peak value before decreasing as the wake forms a super cavity. The physical mechanism responsible for this observed change in shedding dynamics is yet to be fully understood. In the current study, we employed time resolved X-ray densitometry and high-speed videography to study the cavitation dynamics in the wake of a triangular, nominally two-dimensional wedge in a re-circulating water tunnel to understand the underlying mechanisms responsible for cavity formation and shedding. Mach numbers of the bubbly mixture, obtained based on base pressure and void fraction measurements, revealed that the flow transition from subsonic to supersonic coincides with the increase in Strouhal number suggesting the importance of compressibility effects on the wake dynamics.