Effects of gas concentration on cavitation dynamics in a venturi channel

Various aspects involved in the cavitation have been studied for a long time, but due to the difficulty of measuring the velocity fields of a very-fast-occurring flow phenomena, the interaction between the flow and cavitation is not fully understood. We conducted an experiment in the 2D venturi channel, focusing on the evolution of cloud cavitation, under the lowered background pressure (to 0.5 atm) to create conditions for cavitation to occur even at relatively low flow rates. The cavitation bubble formation and the flow field were measured using shadowgraphy, PTV, and PIV at Re = 100,000-131,500. In addition, the amount of dissolved gas in the water flow was controlled through the injection and removal of air in the test section. We found that the amount of cavitation bubble generation increased as the amount of dissolved gas increases, but the point at which cavitation pattern transition from the sheet to cloud was rather delayed. Also, the volumetric growth of cloud cavitation also decreased as the gas content increases. We will further the analysis of the mechanism of cavitation control with the gas concentration, together with the flow field measurements.