NUMERICAL-ANALYSIS OF A SINGLE BUBBLE BY VOF METHOD

In order to examine the feasibility of direct simulation of bubbly flo w, the applicability of the VOF (volume of fluid) method to analyses o f a single rising bubble was examined in this study. Calculated bubble shapes and terminal velocities under wide ranges of Eotvos number and Morton number were compared with the experimental data summarized by Grace et al. Except for the cases in which bubble shapes were spherica l-cap and skirted, the VOF method could predict them well by assigning only eight cells to the bubble diameter. Hence, it was confirmed that some modification of this method will enable us to simulate bubbly fl ow directly under a wide range of flow conditions. The relationship be tween bubble shape and velocity distribution was also examined within the ranges in which the VOF method is valid. It was found that the sec ondary vortex appearing in wobbling bubbles induces a velocity compone nt normal to the bubble interface, and this velocity is one of the cau ses of the wobbling shape of the bubble.