Numerical Simulation of Mass-Transfer Characteristics of a Bubble Rising in Yield Stress Fluids

The mass-transfer characteristics of bubbles rising in yield stress fluids was investigated numerically using volume-of-fluid and user-defined function methods in this study. The CO2 concentration profiles inside the liquid phase near the bubble equator at different bubble diameters, yield stresses, consistency coefficients, and flow indices were observed. The results revealed that the rate of mass transfer decreased with the increase of yield stress, consistency coefficient, and flow index of the liquid phase and the decrease of bubble diameter. Moreover, two empirical correlations for the drag coefficients and Sherwood numbers were developed by introducing one correction factor X for C-D correlation and another correction factor f(c) for Sherwood numbers for correcting the influence of yield stress behavior on bubble motion and mass transfer, respectively. The predictions of the two correlations were compared with the simulated data, and a satisfactory agreement was found.