ID 32

A numerical method for handling arbitrary solid boundaries within the DNS multiphase code Free Surface 3D (FS3D)

 

Abstract:

Aim of this work is the implementation of embedded solid boundaries into the program Free Surface 3D (FS3D); our in-house finite volume code for the direct numerical simulation of incompressible multiphase flows. FS3D uses the Volume of Fluid (VOF) method and the Piecewise Linear Interface Calculation (PLIC) scheme for interface tracking and reconstruction. Because FS3D works with Cartesian grids, a method for arbitrary shape boundary representation is shown. Boundaries are represented by their volume fraction and the PLIC scheme is used to approximate the boundary surface. In FS3D scalar variables are stored at cells centers and velocity components are stored at cell faces; so that control volumes for scalar variables and for velocity components are shifted. Since the immersed boundary is treated as a rigid body of infinite density, velocities will be zero if the respective control volumes contain the boundary. Because of that, a linking strategy is necessary to advect the fluid in boundary-crossed cells when the boundary configuration is such that velocities are zero on at least five faces. These cells are marked as slaves and each is merged to a master cell, which is determined by the normal vector to the boundary surface. An averaged velocity field which is discretely divergence free is used for fluid advection in master-slave couples. Simulations for drop advection on a featured wall are shown.