Interface advection with the TAU code and the CICSAM method on arbitrary grids

Abstract

The DLR computational fluid dynamics code TAU is enhanced with the volume-of-fluid method (VOF) for a modelling of fluid interfaces. Within Tau the compressible Reynolds-Averaged-Navier-Stokes equations are discretized by a finite volume technique. TAU works with both structured as well as unstructured grids. In the pre-processing step the primary grid is split into control volumes, which are again subdivided into tetrahedra. These tetrahedra are cut with a predefined interface to initialize the volume-of-fluid distribution. Thus, the algorithms must be implemented to work efficient with both types of discretizations. For the advection of the interface the CICSAM method (Compressive Interface Capturing Scheme for Arbitrary Meshes) is employed which is far easier to implement when the code is desired to work on unstructured as well as structured grids than geometrical-based methods like PLIC. A further advantage of CICSAM when applied in the TAU code is the fact that the cell information of the primary grid is not explicitly needed. The method is implemented to work with the given dual grid control volume information. The performance of the interface advection is evaluated with the transport of a spherical distribution along the edges of a square grid and a rectangular one transported through an oblique, homogenous velocity field. The test cases are conducted on both structured as well as unstructured grids.