Constrained Flow Past Cavitating Bluff Bodies

Abstract

An experimental program has been carried out to determine the effects of wall interference on the drag and vortex shedding characteristics of cavitating two-dimensional triangular prisms and circular cylinders. The former shapes were chosen to eliminate effects of Reynolds number in interpreting the results. Direct pressure measurements were made to estimate the drag force. The vortex shedding frequency of the cavitating bodies was recorded with the help of a pressure transducer. The gap velocity u1 and the jet contraction velocity uj are shown to be the proper velocity scales to form the drag coefficients and Strouhal numbers for the bluff shapes tested. The drag coefficient was found to increase due to wall interference effects when partial cavitation conditions prevailed. The trend of the drag coefficient data indicated that wall interference effects are relatively small at very low cavitation numbers (σ → σch ) which correspond to choking conditions. As choking conditions are reached, the vortex shedding from the cavitating source becomes intermittent and finally vortex shedding ceases.