Nonlinear interaction between a gas bubble and a suspended sphere

The fully nonlinear interaction between a gas bubble and a suspended sphere is studied using boundary integral method. The violently expanding and collapsing bubble would cause the sphere to move, in reverse, the sphere response can strongly affect the bubble dynamics. Differing from previous studies, we use the auxiliary function method to decouple the mutual dependence between the force and the sphere motion. To validate our model, two experiments are carried out for a spark-generated bubble interacting with a suspended sphere, captured by using a high speed camera. Our numerical results agree well with the experimental data for both cases, in terms of bubble shapes and sphere displacement. We further conduct convergence and sensitivity studies, in which consistent results have been achieved. Then, the effects of two parameters are investigated, i.e., the stand-off parameter (defined as γ=d/Rm, where d is the minimum distance between initial bubble center and the sphere surface, Rm is the maximum equivalent bubble radius) and the size ratio (defined as θ=Rs/Rm, where Rs is the sphere radius). The sphere is pushed away by the expanding bubble and gets attracted towards the collapsing bubble. Bubble motion varies greatly with different parameters. We found the maximum jet impact pressure on the sphere is realized when θ is around 2.