Numerical Simulation for Initial Behavior of Bubbly Flow

Abstract

This papar is concerned with numerical simulation of a bubbly flow which is generated by continuous release of bubbles with various arrangements from the bottom of a vessel in gravitational field. The flow was analyzed as a continuum in which density and viscosity changed owing to existence of the bubbles. The availability of the exact solution of B. B. O.'s equation with constant acceleration during small time interval made it easy to analyze the motion of the bubbles in the flow. The velocity and pressure fields based on one fluid model were calculated using the SIMPLE method. For initially asymmetric arrangement of bubbles or asymmetric release position, the flow tends to be unstable, even if asymmetry is slight. For initially symmetric arrangement, small bubbles, released from symmetric bottom position of a vessel, are caught in vortices generated by rising bubbles and the flow. tends also to be unstable because of the slight difference of number density of the bubbles in the vortices. This tendency becomes to be weak when large bubbles are mixed with the small bubbles.