3D toroidal bubbles near a rigid wall

Abstract

A new 3D model of jet impact in the context of bubble dynamics is presented. Our major concern is the formation and evolution of toroidal bubbles due to the jet impact. To this end, an improved model for 3D bubble dynamics is first proposed to tackle the wild numerical instability that occurs prior to and during the impact; a novel scheme based on least squares is devised to damp out the "noise" part of the solution, thus ensuring a smooth transition from a singly-connected bubble to a doubly-connected toroidal bubble. The vortex-ring model of Wang et al. is extended to 3D. Although our results indicate marked differences from previous axisymmetric results in terms of the lifetime of the toroidal bubble as well as some fine features of the bubble profile, the essential physics associated with the jet impact, such as the circulation around the torus and the rebound of the toroidal bubble, is well captured in our new model. We also present, for the first time, preliminary results for full 3D cases in which buoyancy effects lead to oblique jetting. Some intriguing phenomena are discovered in the rebound phase. © 2001 Kluwer Academic Publishers.