Numerical Simulation of Bubble and Droplet Dynamics using Partitioned Solvers

Abstract

Bubbles and droplets can be simulated as a problem involving Fluid-Structure Interaction (FSI). The interface between the liquid and the gas is then conceived as a zero thickness structure. The position of the interface is determined by the equilibrium between surface tension effects and the pressure jump across the interface. Most techniques frequently used for studying bubble and droplet dynamics, such as Level Set or Volume Of Fluid, use monolithic schemes. The flow on both sides of the interface and the position of the interface are calculated in a single code. Here, a partitioned approach is presented. The flow in the liquid is calculated with a black box commercial code. The position of the interface is calculated with a structural solver, using a reduced order model of the fluid solver to obtain implicit coupling between both solvers. The reduced order model, based on modal analysis, is build up during the coupling iterations of a time step. This model is applied to three axisymmetric problems: an oscillating water droplet in air, an air bubble rising in stagnant mineral oil and the growth and detachment of an air bubble from a vertical needle, submerged in quiescent water.