Effect of surface roughness on cloud cavitation

Cloud cavitation is a highly unsteady phenomenon that occurs in low pressure regions, that can cause severe pressure fluctuations and erosion of material. It is characterized by the formation and collapse of large clouds of vapor bubbles which makes the flow unstable. The increase in noise and damage caused by this represents serious problems in marine propellers and turbines. This study examines the influence of surface roughness on cloud cavitation over a Venturi. Micro scale roughness elements, of the range 5-60μm were induced on the surface on the Venturi through 3D printing with various surface patterns. Surface roughness modifies the flow field and cavitation shedding frequency. In general, rough walls introduced extra near-wall turbulence and vorticity, affecting the re-entrant jet that drives cloud detachment.

In this experiment, we will be able to determine how various roughness can alter the time period of the cavitation cycles, the change in cavity breakup mechanism such as re-entrant jets and vortex structures. The findings will help us indicate if surface roughness is promoting enlarging the cavitation zone and dampening the high-frequency oscillations of cloud cavitation. By analyzing the flow over a rough Venturi, we will get an insight into how modest surface roughness significantly alters the cavitation pattern, shedding frequency, and flow structure compared to a smooth surface. Understanding this effect is crucial for gaining insight into cavitation control and the surface textures that can be used to influence cavitation intensity and stability in hydraulic devices.