Bubble Formation in Yield-Stress Fluids Using a Coupled Level-Set and Volume-of-Fluid Method

摘要

The bubble formation under the influence of orifice diameter submerged in yield-stress fluids was studied numerically using a coupled level-set (LS) and the volume-of-fluid (VOF) method and was in contrast with that seen in Newtonian fluids. The bubble formation process had a good consistency by virtue of comparing numerical simulation and experiment. The process of bubble formation could be divided into two parts, bubble expansion stage and stretch stage. The influence of orifice diameter and liquid rheological characteristics (consistency coefficient, flow index, and yield stress) on the bubble formation parameters (the bubble formation time, detachment volume, and aspect ratio) was investigated. The results revealed that the bubble detachment volume increases with the increase of orifice diameter, consistency coefficient, flow index, and yield stress. In different kinds of fluids, the formation time and detachment volume of bubbles in the shear-thinning fluid were the lowest, followed by the Newtonian fluid, and finally, in yield-stress fluids.