Abstract
We present the results of three-dimensional direct numerical simulations of the motion of a gas bubble rising in shear-thinning liquids. The simulations are carried out by a coupled level-set/volume-of-fluid (CLSVOF) method which combines some of the advantages of the volume-of-fluid (VOF) method with the level-set (LS) method. In our study, shear-thinning liquids are modeled using the Carreau model, and the motion of a rising gas bubble in shear-thinning liquids depending on Carreau model parameters are three-dimensionally simulated. It is shown that the motion of a rising gas bubble largely depends on Carreau model parameters. The Carreau model parameter, β, specifies the critical value of shear rate for which the viscosity drops off rapidly from the zero shear rate viscosity. When the specified critical shear rate is very high, a rising bubble behaves as if the motion was in a Newtonian fluid system. Otherwise, we observe distinct shear-thinning properties in the bubble motion. Using numerical analysis, we can understand in detail bubble morphology for non-Newtonian two-phase flow systems. We also discuss the effectiveness of numerical analysis for understanding such systems.
