Dependence of cavitation bubble impact onto a body on liquid pressure

The effect produced by liquid pressure during the impact of a cavitation bubble on the surface of a body was numerically studied. The liquid under study was water; the material of the body was copper-nickel alloy; the bubble was initially spherical (radius 1 mm), touched the body, and filled with vapor in the saturation state. The liquid pressure pL varied from 1 to 7 bar. The impact on the body resulted from the action of a cumulative jet arising on the surface of the bubble during its collapse. The main attention was paid to the short-term initial phase of the impact when the maximum pressure on the wall was of the order of the water hammer pressure pwh , corresponding to a rigid wall. It was shown that the cumulative jet velocity and radius increase from 115 to 317 m/c and from 38 to 43 µm , respectively, with increasing pL . Throughout the pL range considered, the initial stage of the cumulative jet impact developed similarly to the known case of the spherical drop impact. The body surface pressure first reached the water hammer pressure level. Then the pressure on the body surface at the center of the impact domain decreased monotonically, whereas at the periphery it initially increased to about 2.5 pwh and after that decreased. Initially, the deformations in the body in the impact center vicinity were elastic at pL = 1 bar and plastic at pL = 4 and 7 bar. Then they became plastic at pL = 1 bar. With increasing pL , the plastic zone significantly increased, its geometry greatly changed. The jet impact resulted in a circular micropit appearing on the body surface. With increasing pL , it became more pronounced