Fluid Field Solver OpenFOAM

OpenFOAM is used to simulate the fluid field within an FSI-analysis. It is an open-source and freely available software package for FVM-analysis. Two specific aspects have to be mentioned: compilation and problem setup. All other aspects are like in standard OpenFOAM.

Compilation

Libraries

OpenFOAM is only available for a Linux environment. To be used within an FSI-simulation, some changes to the standard installation have to be made. First, a standard installation should be performed. The source code can be downloaded from www.openfoam.org. The version, the institute currently works with, is 1.6.x. For the installation, the guidelines on the user guide, the web site, or the forum, can be used. After the installation is finished and tested, some changes to the source code of the OpenFOAM libraries are necessary. These changes are restricted to the parallel communication library of OpenFOAM and necessary for enabling communication with CoMA. There exists an svn-repository, which contains a README-file with general instructions and the new source code files. The svn-repository is hosted on the same server as the carat repository. The current IP is 129.187.141.99 and the folder is named "OpenFOAM". Follow the instructions in the README-file to replace the code parts and recompile everything.

Solvers

After a succesfull installation of OpenFOAM, specific FSI-solvers for OpenFOAM have to be installed, following the typical Foam approach. These solvers can also be found in the svn-repository. There are different solvers for different tasks. The solver named "implicitFsiFoamTurb" is e.g. a solver for implicitly coupled FSI-simulations with turbulence modelling (RANS and LES).

Problem Setup

The problem setup is based on a typical OpenFOAM case used for a single-field analysis on a moving domain. Setting this up is explained e.g. in the OpenFOAM user guide or in the tutorials.

Hint: Do not forget to set the velocity boundary condition of the moving patch to type "movingWallVelocity".

One additional file has to be added to the standard case, the file "couplingProperties" in the constant folder. It contains the following parts:

//name of coupling patches
coupledPatchNames  2(beam_top beam_bottom );
coupledPatchTags   2(1 1);

//density of Fluid
densityFluid  1000.0;

In this case, the interface mesh of the coupled surface consists of two OpenFOAM patches with names beam_top and beam_bottom. Both have the same mesh tag, used to match Carat++ and Foam interface meshes. The density of the fluid has to be specified to evaluate the surface forces correctly.