Abstract
The wall effects on the floating motion of bubbles in shear-thinning fluids were investigated with the numerical method. The interface between the bubble and the liquid phase was tracked with the volume of fluid (VOF) method. The Carreau model and the continuous surface tension model were used to calculate the rheological properties of the shear-thinning fluid and to compute the surface tension between gas and liquid phases, respectively. For different rheological indexes, the wall effects on the bubble shape, the liquid-phase flow field and the bubble terminal velocity were studied in detail. The results show that, the strong wall effect or the weak shear-shining effect can hinder the bubble deformation and the formation of wake vortices, and can reduce the bubble terminal velocity. Among all physical parameters, the bubble terminal velocity is most liable to the wall effect. For the strong wall effect and the strong shear-shining effect, the high-shear-rate region will occur near the wall, which results in a significant decrease in the apparent viscosity of the liquid phase near the wall.
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