3D jet impact and toroidal bubbles

A three-dimensional model of collapsing bubble with jet formation and impact is presented in this paper. The strong instabilities of the jetting process, impact, iind toroidal bubble rebound are dampened by a new smoothing scheme based on least squares, thus enabling a smooth transition from a singly connected bubble to a doubly connected toroidal bubble. A high order of mesh regularity is maintained by a mesh refinement procedure. The circulation of the How around the gaseous tube of the toroidal bubble is modelled by a generalization of the vortex ring method of Q. X. Wang et al. (Comput. Fluids 25, 607 (1996)). Although our results indicate some differences from previous axisymmetric results in terms of time to impact and fine features of the evolving toroidal bubble profiles, the essential physics associated with the jet impact. such as the circulation around the torus and the rebound of the toroidal bubble, are well captured in the new model. We also present, for the first time, results for fully three-dimensional bubbles in which buoyancy effects lead to oblique jetting. (C) 2001 Academic Press.