Analysis of Dynamics of the Cloud Cavitation and its Control

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It is well known that a cloud cavitation is one of the most destructive forms of cavitation. In the present study, the set of equations for the motion of a spherical bubble cloud is formulated and the behavior of bubble clouds are simulated numerically under the situation of sudden change of surrounding pressure. To study the collapse of cloud cavitation more accurately, the internal phenomena of each bubble and the compressibility of liquid are considered in the governing equations. An inward propagating shock wave is formed during the collapse of bubble cloud and the shock wave is focused in the center region of the cloud. This makes a violent bubble collapse, which cause a high emitted pressure from the bubbles, which is several hundreds times larger than the single bubble collapse. Furthermore, a new numerical method for simulating cavitating flows around hydrofoil is developed. Cloud cavitation is modeled with perfectly spherical bubbles whose radii change with Rayleigh-Plesset equation. The bubbles are also allowed to have slip velocities so that the bubble accumulation could be simulated. Psedocompressibility concept for incompressible flow simulation is extended for the present systems of equations for efficient and robust computations. Computations of two-and three-dimensional cavitating flows verify the present method and show its capability to the practical applications.