Numerical Simulation of Near-Wall Multi-Bubble Collapse with Fluid-Structure Coupling Method

The impact of the cavitation jet on metal surfaces is mainly due to the water hammer effect generated by the high-speed micro-jet near the wall during the collapse of near-wall cavitation bubbles. This paper adds a dynamic pressure to the fluid boundary condition and proposes a numerical analysis model that incorporates Fluid-structure coupling to investigate the near-wall multi-bubble collapse. In this study, titanium alloy was used as the solid wall material, and direct numerical simulation based on the VOF model was employed to the numerical simulations of the collapse of multi-bubble near the wall with different initial bubble sizes at a non-dimensional distance y=h/R=2 and a bubble spacing of 2 mm. The results show that the collapse of multi-bubble near the wall follows an “outside-in” sequence, with the collapse rate gradually increasing as the process progresses. With increasing initial bubble radius, the time required for collapse becomes longer, and the maximum collapse pressure increases accordingly. Moreover, the collapse pressure of multi-bubble far exceeds the sum of the collapse pressures of single-bubble, with a maximum collapse pressure of up to 47.5GPa. The deformation and residual stress on the titanium alloy surface caused by the collapse also increase with increasing bubble radius, and the surface deformation gradually increases as the collapse pressure increases. The maximum deformation is 8.87μm. The residual stress value on the titanium alloy surface decreases with increasing wall depth and radial distance.