Numerical Analysis of Temperature Fields inside Nonspherical Bubbles in the Final Stage of Collapse

The temperature fields inside a collapsing bubble near a plane rigid wall are investigated. We develop a numerical method based on the boundary element method combined with the finite volume method. In this method, the adaptive unstructured grids which are generated by Delaunay triangulation are used inside the largely deformable bubble to consider the heat transfer of the internal gas. We compare the present numerical results with those using structured grids. The result shows that the present method has sufficient accuracy to investigate the bubble motion. It is also shown that the present method can be applied to the analysis for the temperature fields inside tiny bubbles in which the thermal boundary layer is thick. Since the unstructured grids are more flexible for the regeneration and resizing of grids, the present method is applicable to the dynamics of toroidal bubbles by taking the thermal diffusivity of the internal gas into account.