[ncl94]

Hello all,


In OF we see a lot of tutorials using 2D cases (pitzDaily, cavity, etc...), but this problems don't use any internal geometry, like the 3D case of motorBike. In my problem, I want to simulate a tube immersed in a fluid, which due its symmetry I can simulate in 2D, like in the figure below. I was able to do the 3D case, by using snappyHexMesh (like in the motorBike tutorial), but how can I do a similar thing for a 2D case?

[AtoHM]

You take either the front or the back face and use this with the extrudeMesh utility with 1 layer to get a pseudo-2d-mesh which OpenFOAM requires. Google for a template extrudeMeshDict file to use.

[ncl94]

Thank you, @AtoHM ! I was able to find the extrudeMeshDict template. Unfortunately, OF documentation on extrudeMesh is almost nonexistent, making it hard to figure out what are the commands and what they do. I played around with the template but couldn't figure out a way to achieve what I want.


For instance, I have a blockMesh which creates a CV with a box shape defined by the following vertices for main diagonal: (0.25, 0.25, 0.25), (-0.75, -0.25, -0.25). My tube is positioned at (0,0,0) with its longitudinal axis colinear to x-axis. Do you know what commands could I use to get the extrude mesh to be defined by (0.25, 0.25, 0.005), (-0.75, -0.25, -0.005), which mean the thickness I am extruding is 0.01? The code I am using is the following:


extrudeModel linearNormal;

thickness 0.01; // used by plane extrusion

nLayers 1;
expansionRatio 1.0;

linearNormalCoeffs
{
thickness 0.01;
}

[ncl94]

Also, would you know what is the correct procedure? *Meaning the correct order of steps (e.g blockMesh -> snappyHexMesh -> extrudeMesh)

[AtoHM]

I don't really get that part.

Originally Posted by ncl94

For instance, I have a blockMesh which creates a CV with a box shape defined by the following vertices for main diagonal: (0.25, 0.25, 0.25), (-0.75, -0.25, -0.25). My tube is positioned at (0,0,0) with its longitudinal axis colinear to x-axis. Do you know what commands could I use to get the extrude mesh to be defined by (0.25, 0.25, 0.005), (-0.75, -0.25, -0.005), which mean the thickness I am extruding is 0.01?

I have done this with blockMesh > snappyHexMesh > extrudeMesh. There are probably other ways to use it too, but this gave me maximum control of the mesh.
Going from your first post with the image, I assume you want to run this "face" as a 2d simulation. The visible surface is "FRONT" the one on the other side is "BACK", this extrudeMeshDict should give the correct result:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.3.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      extrudeProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
constructFrom patch;
sourceCase "$FOAM_CASE";
sourcePatches (FRONT);
exposedPatchName BACK;

flipNormals false;
 
extrudeModel        linearNormal;
 
nLayers             1;
expansionRatio      1.0;
 

linearNormalCoeffs
{
  thickness .01; //extrude 1 cm
}
 
mergeFaces false;
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

[ncl94]

I tried to be a bit formal I guess haha ... but what I meant is that if I do exactly as in the piece of code you posted in your last reply, I won't slice the middle of the mesh, where my tube is, but it will generate a mesh with 0.01 thickness from the FRONT boundary as in your example. I actually need something to do exactly the same thing but with an offset from the sourcePatch. Anyway, I appreciate the help.