An Analysis of the Immersed Boundary Surface Method in foam-extend

Abstract

The Immersed Boundary Surface method is an implementation of the Immersed Boundary method in the latest versions of foam-extend, a fork of the free, open source computational fluid dynamics (CFD) software OpenFOAM. Instead of using body-fitted meshing methods, the Immersed Boundary method merges objects and boundaries into a uniform background mesh. While the Immersed Boundary method contains many different merging approaches, the Immersed Boundary Surface method merges objects represented by triangulated surface meshes into the background mesh in a manner similar to the cut-cell approach. In this thesis, the implementation and limitations of the Immersed Boundary Surface method in foam-extend 4.1 nextRelease branch are investigated and analysed. In foam-extend, the Immersed Boundary method was already implemented in previ ous versions using polynomial fitting and based on the discrete ghost-cell approach, but was heavily modified in version 4.1. A detailed description of the newly im plemented Immersed Boundary Surface method in foam-extend 4.1 nextRelease branch as well as a comparison to the implementation in previous foam-extend versions is given. The impact of using the cut-cell approach on the choice of the background mesh is shown in guidelines for mesh refinement. The limitations of the Immersed Boundary Surface method are investigated using simple test cases, focus ing on the mass conservation. Furthermore, the implemented Immersed Boundary wall functions are compared to established body-fitted wall functions on different test cases.