MUSIG modeling and evaluation of nitrogen bubble coalescence in a bottom-closed vertical tube

A MUSIG model is numerically resolved for the coalescence process of dispersed small nitrogen vapor bubbles into big bubbles in a bottom-closed vertical tube. The effects of turbulence, laminar shear as well as wake entrainment on bubble collision and coalescence are taken into account. Then photographic experiments are conducted to evaluate the model, using a high-speed CCD camera at an acquiring frequency of 1000 frames/second. Comparison of numerical results against the experimental data demonstrates that the MUSIG model can give satisfactory predictions of the bubble diameter, bubble velocity, as well as the height of Taylor Bubble Formation (TFB). The numerical results also contribute to understanding of the phenomenon observed in the experiments. However, it is also found that beyond the height of TFB, the numerical results deviate from the experimental data, which indicates that beyond that height, the MUSIG model becomes invalid.