Numerical Simulation of Micrometer-Sized Bubble Collapse near a Rigid Boundary

Collapse of a single micrometer-sized cavitation bubble near a rigid boundary was numerically simulated by using volume of fluid (VOF) multiphase model with considering surface tension of vapor-liquid interface, liquid viscosity and compressibility of gas in bubble. The detailed flow field was obtained during a bubble collapsed near to the wall and the effect of the non-dimensional stand-off parameter γ on the collapse behavior of bubble was discussed. Moreover, the cavitation erosion on the wall was revealed for different γ. The computational results show that the bubble center approached the wall, the pressure decreased in the high pressure zone above the bubble prior to formation of jet, collapse time delayed and the maximum jet velocity decreased as γ decreased. The simulated results verified that the bubble collapse near the wall can produce shock wave and micro jet, both of which can make the wall subjected to an impulse pressure. The cavitation-erosion mechanism on the wall was significantly determined by the stand-off parameter γ. Compared with micro jet, shock wave had a more remarkable cavitation damage on the wall. The action radius of micro jet on the wall was about 10 μm, which led to the spot corrosion pits. The area swept by shock wave was relatively wide and the effective action radius on the wall was about 1 mm for γ=2.0, which led to the annular corrosion pits with a seriously eroded center.