Finite Element Simulation For Two-phase Flow with a Decoupled Fluid Interface
Congress: CHT
ABSTRACT:
In this research, finite element numerical simulation is used to describe bubble dynamics in two-phase flows. The accurate simulation of interface dynamics in two-phase flows is of crucial relevance for numerical analysis of two-phase heat transfer. The simulation is achieved by solving the incompressible Navier-stokes and energy conservation equations for two-phase flows, discretized through the Finite Element Method (FEM), where the interface and the fluid meshes are not explicitly connected. Two meshes are used, a fixed one for the fluid flow, and a moving mesh which describes the interface movement between fluids. Fluid properties are smoothed out to avoid numerical instabilities in the transition from one fluid to another. Surface tension is implemented according to the well-known continuum surface tension model, using the Laplace-Beltrami operator for curvature computation. Surface tension force is added explicitly to the Navier- Stokes equations as a volume force through the gradient of a Heaviside function, therefore the momentum equation is solved using a one-fluid approach. To prove that such an interesting numerical scheme is stable and accurate, we present two test cases, consisting of a bubble rising due to gravity. The first case explores a small difference in viscosity and density and the second one presents a more aggressive difference in properties across both fluids, and a smaller surface tension, exposing a more difficult simulation. Both cases resulted in stable bubbles, with qualitative results agreeable to the literature.