THE EFFECT OF BUOYANCY ON PHASE DISTRIBUTION IN DISPERSED TURBULENT TWO-PHASE FLOWS

Abstract

Advanced generation three-dimensional (3-D) two-fluid models and computational multiphase fluid dynamic (CMFD) solvers give good predictions of dispersed flows on earth (i.e., at 1 g), where the lift, wall, and turbulent dispersion forces determine the lateral void fraction distribution. However, for microgravity (μ-g) conditions these buoyancy-related forces become quite small and two-fluid model predictions are generally inadequate. This implies that some of the physics lost during ensemble averaging was not included back into the two-fluid model with the closure laws that were used.

Recent modeling advances that include the effect of the phasic velocity fluctuations on the phase distribution are presented. The resultant two-fluid model was evaluated and compared with various data sets for steady, fully developed turbulent conditions using a novel one-dimensional (1-D) CMFD solver that is numerically very efficient. It was found that with the addition of these new physical mechanisms to the closure laws, one is able to achieve good predictions of both the gas/liquid and solid/liquid dispersed phase distribution over a wide range of particle/bubble buoyancies and gravity levels.

Keywords:

• Dispersed two-phase conduit flow
• Phase distribution
• Two-fluid models