Bubbly Cloud Dynamics and Cavitation

In many cavitating liquid flows, when the number and concentration of the bubbles exceeds some critical level, the flow becomes unsteady and large clouds of cavitating bubbles are periodically formed and then collapse when convected into regions of higher pressure. This phenomenon is known as cloud cavitation and when it occurs it is almost always associated with a substantial increase in the cavitation noise and the potential for material damage associated with the cavitation. These increases represent serious problems in devices as disparate as marine propellers, cavitating pumps and artificial heart valves. This lecture will present examples of the phenomenon and review recent advances in our understanding of the dynamics and acoustics of clouds of bubbles and cloud cavitation. Both analyses of these complex multiphase flows and experimental observations will be used to identify the key features of the phenomenon and the parameters that influence it.