INFLUENCE OF GAS-DENSITY ON THE STABILITY OF HOMOGENEOUS FLOW IN BUBBLE-COLUMNS

Stability analysis is used to show that an important parameter determining the stability of homogeneous bubbly flows in a bubble column is the Richardson-Zaki exponent n in the bubble swam velocity relationship U(swarm) = upsilon(infinity)(1 - epsilon)n. Analysis of bubble swarm velocity shows that with increasing gas density the value of this exponent decreases; physically this mean that increasing gas density results in reduced interaction between neighboring bubbles and, consequently, reduced chance of propagation of instabilities. This provides a rationalization of the experimental observation that the influence of increased gas density, rho(G), is to delay the transition from homogeneous bubbly flow to churn-turbulent flow.