An Analysis of the Immersed Boundary Surface Method in foam-extend
Typ
Examensarbete för masterexamen
Program
Applied mechanics (MPAME), MSc
Publicerad
2022
Författare
Döhler, Jan Erik
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
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.
Beskrivning
Ämne/nyckelord
CFD, Immersed Boundary Method, Immersed Boundary Surface Method, OpenFOAM, foam-extend, Motion fluxes, Wall functions.