Numerical Analysis of the Dynamics of Toroidal Bubbles Considering the Heat Transfer of Internal Gas

Abstract

This paper describes a new numerical method to compute the motion of a toroidal bubble that is formed after the liquid microjet threads the bubble. We use the boundary element method (BEM) combined with the finite volume method to calculate the toroidal bubble dynamics considering the heat transfer inside the bubble. The unstructured triangle grids are generated inside the bubble. We investigate the bubble collapse near a plane rigid wall. The results show that the initial radius affects the motion of the toroidal bubble, the temperature fields inside the bubble and the pressure fields outside the bubble. When the initial radius is small, the internal thermal boundary layer becomes thick and the bubble collapse is accelerated. This violent collapse induces the extremely high pressure region near the point of liquid-jet-impact. The wall pressure, therefore, becomes locally much high when the tiny bubble collapses near the wall.