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samiam1000 September 30, 2011 06:37

blockMesh
 
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Dear all,

I wanna simulate the wind over a certain area.

I tried different tutorials and everything seems to work properly. Now I am trying to start with my simulation.

I have a problem with the 1st step, that's to say the "blockMesh".

In fact, I have to create a a block and then I will mesh it. The point is that I don't want to mesh a cube, but a "cube" whose lower face is my terrain. The point is that the edge of my terrain don't have the same altitude z (see the picture).

Does anyone know how I can solve? What should I do? Any hint?

Thanks a lot,

Samuele

Bernhard September 30, 2011 06:51

Maybe you can consider using snappyHexMesh?

samiam1000 September 30, 2011 07:43

Dear Bernhard,

thanks for answering. Well, snappy is what I am gonna use afeter block.

How can I detect the volume that I wanna mesh without defining a block?

Thanks a lot,

Samuele

eysteinn September 30, 2011 08:02

Quote:

Originally Posted by samiam1000 (Post 326226)
Dear all,

I wanna simulate the wind over a certain area.

I tried different tutorials and everything seems to work properly. Now I am trying to start with my simulation.

I have a problem with the 1st step, that's to say the "blockMesh".

In fact, I have to create a a block and then I will mesh it. The point is that I don't want to mesh a cube, but a "cube" whose lower face is my terrain. The point is that the edge of my terrain don't have the same altitude z (see the picture).

Does anyone know how I can solve? What should I do? Any hint?

Thanks a lot,

Samuele

Hi Samuele,

I'm not sure if this is what you are looking for but here goes:

What I would suggest (maybe there are other way and then I would glad like to hear them).

Create a closed surface (stl file ), in your case a box with the bottom as your terrain.
This is your "wind tunnel".
You can name the parts of your surface (e.g. inlet, outlet, terrain and walls )using Blender ( see http://www.cfd-online.com/Forums/ope...cii-stlbs.html ).
Then you create a box in blockmesh that is slightly larger than your stl geometry. When that is all done you move to snappyHexMesh to trim of the excess cells and do refinements of the mesh.

/Eysteinn

grjmell September 30, 2011 08:34

I've done exactly this before.

I did this:
1. create stl file of terrain (position centre at 0,0,0)
2. create blockMesh with the same (or tiny bit smaller) dimensions of your stl in x-y direction and whatever extent you require in z direction
3. find the lowest point in your stl (i.e. lowest z-value)
4. translate stl by that z-value. this makes the lowest point of your stl fall onto the bottom of your blockmesh (say at z=0)
5. run blockmesh and snappy and you have what you need. works fine for me.

samiam1000 September 30, 2011 10:09

Hi all,

I think that both your ideas are good.

I am gonna try grjmell's one since it looks simpler (since it does not involve Blender)..
What I wanna ask to grjmell is why he translates the stl. Can't I create a box where the stl is? Why should I move it to have z=0??
I don't care about this, right??

I will try and then I'll let you know.

Thanks again,

Samuele

grjmell September 30, 2011 11:16

Yes translation is optional as long as you encompass all the stl (z extent) with your blockmesh


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