Study of cavitation in the wake of a cylinder

Cavitation refers to formation of bubbles in a flow and subsequent dissolution in the flow. The bubbles are formed when the low pressures is below vapour pressure at the given temperature. The pressures may be reduced due to flow conditions or imposed acoustic field. Depending on origin cavitation may be classified into acoustic cavitation and hydrodynamic cavitation. Acoustic cavitation is found helpful in various field like biological and medical. Hydrodynamic cavitation can occur in at throat of venturi or downstream of nozzle where the pressures are low. Hydrodynamic cavitation is known to have many undesirable effects in hydroturbomachinery reducing efficiency, generating noise. Cavitation in wake is a type of hydrodynamic cavitation occurring in the vortex core in the wake region for flow past an obstacle are bodies. Cavitation can occur in wakes, and yet all wakes are not cavitating flows. In these zones the pressures are generally low due to fluctuating velocities. The bubbles get more time to reside, grow and subsequently collapse. Considering the harmful effects, attempts are made to understand it and try to propose method to control it. Experimental studies were carried out to understand the properties of the phenomenon. The vapour volume fraction was found to increase with a decrease in cavitation number. The pressures in that cavitating region were found to be fluctuating and the Strouhal number was calculated. Pressure fluctuations due to cavitation, photographs and video clips, were also taken for each test body at different flow and cavitating conditions to understand the flow better.