NUMERICAL SIMULATION OF BUBBLY FLOW BY AN IMPROVED VORTEX IN CELL METHOD
A simulation method for gas-liquid bubbly flows entraining small bubbles is proposed. It is based on the Vortex in Cell (VIC) method originally presented to simulate incompressible single-phase flows. The staggered grid discretization method and the vorticity correction method, which were proposed for the VIC method simulating single-phase flows by the authors’ prior study, are employed. The liquid velocity field is discretized with vortex elements, and the time evolution of the bubbly flow is simulated by calculating the behavior of each vortex element and the bubble motion through the Lagrangian approach. The proposed method is applied to the simulation of a bubble plume in a water tank to discuss the validity and applicability. Small air bubbles are released successively from the base of the tank, and their rise due to the buoyant force induces the water flow around them. The simulation at the starting period of the bubble release highlights that the rising bubbles induce vortex rings at their top and that a bubble cluster appears owing to the entrainment of the bubbles into the vortex rings. The rising velocity of the top of the bubbles is proportional to the square-root of the flowrate of the released bubbles, being consistent with the existing theoretical and numerical investigations. The simulation also demonstrates that the developed bubble plume having jet characteristics is successfully captured.
gas-liquid two-phase flow, computational fluid dynamics. bubbly flow, bubble plume, vortex method.