FAQ/Preprocessing

1 FAQ Section 5: Preprocessing

Preparing the simulations

1.1 How to quickly change the mesh with blockMesh

A description how to achieve this with m4 can be found here: How to quickly change the mesh with blockMesh

1.2 How do I set up a two-dimensional axisymmetric problem?

You use a contributed utility called makeAxialMesh.

1.3 How to export a Fluent mesh in ASCII?

For more information, read these posts:

• ANSYS Meshing & Geometry - ANSYS to Fluent mesh export in ASCII format post #2
• ANSYS Meshing & Geometry - ANSYS to Fluent mesh export in ASCII format post #11
• OpenFOAM Other Meshers: ICEM, Star, Ansys, Pointwise, GridPro, Ansa - Fluent3DMeshToFoam post #48
• OpenFOAM Other Meshers: ICEM, Star, Ansys, Pointwise, GridPro, Ansa - Fluent Mesh (XP32) to OpenFoam

1.4 How to convert Fluent mesh to OpenFOAM?

Read these wiki pages:

• FluentMeshToFoam
• Fluent3DMeshToFoam
• Howto importing fluent mesh with internal walls
• Import a fluent mesh with interfaces

1.5 Why do I always get the error message "cannot find file" when converting a mesh?

For example, you're trying to convert a Fluent mesh to OpenFOAM and you get this error message after you run the conversion utility:

Create time
 
--> FOAM FATAL IO ERROR: 
cannot find file
 
file: /home/ofuser/Desktop/system/controlDict at line 0.
 
    From function regIOobject::readStream()
    in file db/regIOobject/regIOobjectRead.C at line 73.
 
FOAM exiting

Well, the error message should be self-explanatory: it cannot find a file that doesn't exist, namely the file system/controlDict. This is because OpenFOAM's applications almost always need a configured case folder to work in, so that it can know that it can operate within that folder and what are the settings to be used for doing what you want it to do.

Confused? Please read and study the chapter 2 of the OpenFOAM User Guide, which has 3 tutorials which explain most of the bases of what's needed for using OpenFOAM. Then study the tutorial case incompressible/icoFoam/elbow, where you will find a fully prepared cases folder and the file elbow.msh which has the mesh to be converted from Fluent format to OpenFOAM format. The script Allrun that is present in the parent folder incompressible/icoFoam/ has the steps for running this case, but essentially it sums up to running these commands:

fluentMeshToFoam elbow.msh
icoFoam
foamMeshToFluent
foamDataToFluent

The first one is what you're looking for. Then it runs the solver and then it runs the commands for exporting the mesh and then results to Fluent format.