NUMERICAL-METHOD FOR CALCULATION OF SURFACE-TENSION FLOWS IN ARBITRARY GRIDS

This paper outlines a scheme to define and track interfaces in an arbitrary quadrilateral grid by making use of a single fractional volume of fluid (VOF) variable to describe the distribution of the liquid phase in a gas-liquid-particles flowfield. The present methodology, however, represents a substantial refinement over the original VOF programs in that nonorthogonal, body-fitted, and even deforming grids can be used, and the gas and liquid phases can take on totally different properties, including compressibility and incompressibility. The interface is unambiguously defined; it either forms a closed loop or terminates at boundaries with specified wall adhesion angles. Then, local curvatures can be estimated and surface-tension forces determined and applied to the acceleration of local velocities. Furthermore, the availability of the interface orientations with respect to the computational cell boundaries enables a higher-order estimate of the appropriate volume of liquid (as vs gas) that is to be fluxed across a cell boundary. The rewards for this added sophistication are superior liquid contiguity and shape preservation properties compared with simpler interface tracking methods. Examples demonstrating the versatility of the code in two-phase flow applications are presented.