Numerical study on stress in a solid wall caused by the collapse of a cavitation bubble cloud in hydraulic fluid

Abstract

The stress in a solid due to the collapse of a bubble cloud in hydraulic fluid is investigated by the numerical simulation, which considers the fluid-structure coupling and employs the bubbly flow model with Euler-Lagrange method. The dynamics of the bubble at the subgrid scale is described by the Keller-Miksis equation. Heat transfer at the bubble interface is considered to reproduce thermal damping effect. As the result of the fluid-structure coupling simulation, the high von Mises stress region is observed in the solid due to the collapse of the bubble cloud attached on the solid surface, and the propagation of longitudinal and transverse waves in the solid is reproduced. As the standoff distance YC from the solid surface to the center of the bubble cloud decreases, the peak von Mises stress in the solid increases, taking a maximum at YC=0.4RC, and then decreases. Thus, the peak von Mises stress is highest under the condition that the bottom quarter of the bubble cloud is on the wall. Due to the increase of the initial void fraction and the decrease of the initial bubble radius in the bubble cloud, the collapse pressure of the bubble cloud increases. Under certain conditions, the peak von Mises stress can be higher than the 0.2% yield stress value of 250MPa for a cast iron. This is expected to induce cavitation erosion of the solid surface.