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Jack February 11, 2003 11:39

mesh in gambit
if we put a small object such as plane in to a big wind tunnel(3D), how can we mesh it so that the mesh around the plane is very dense and becomes coarser and coarser to the wall of wind tunnel.


Marc February 11, 2003 14:27

Re: mesh in gambit
You probably don't want to use tetrahedrons. I would use a C-Grid, which is wrapped around the tip of the plane. Then you have the possibilies to change the density normal to the plane's surface. Also, because of the diverging element edges, you will not get too bad aspect ratios.
Was it possible to understand this? Hope I did not confuse you.
Greetings, Marc

Jack February 11, 2003 21:51

Re: mesh in gambit
hi, marc, thanks for your response. I am still not very clear about how to mesh this 3D problem. what I did is like this. 1 creat the plane (volume 1 ) 2 creat the wind tunnel (Volume 2) 3 Subtract V1 from V2 4 Mesh plane's surfaces 5 mesh volume 2

but it turns out not the one I want. I want the grids around the plane refined, but it seems all the grids are uniform. I think it has nothing to do with the Shape of the grid. it has to be something with the mesh method. thanks!


Marc February 12, 2003 07:27

Re: mesh in gambit
Dear Jack,
I am not a Gambit user, so maybe I got your question wrong. Do you like to mesh with tetraherdrons or hexaherdrons? If you want to create a hex mesh, one volume will not be enought. You will have to divide the region around the plane into so called blocks (which are each hexaherdrons) and then create a block struktured c-grid. Maybe there is another way in Gambit, which I don't know. Meshing with tetrahedrons will be much easier. Mesh the plane, as fine as you like (surface mesh - 2D) , then mesh the outer surface (wind tunnel) much coarser (also 2D). The 3D fluid mesh should then grow from inside (fine) to outside (coarse). Did that help?
Greetings, Marc

ff February 12, 2003 10:47

Re: mesh in gambit
Dear Jack,

Look in gambit UM for "size functions".

This will solve your problem.



Mitja March 4, 2003 07:40

Re: mesh in gambit
I've got the same problem as Jack. I want mesh the Ahmed model in Gambit and I have meshed some extra edges that I have first created on the faces model, in order to refine the grid in particular zones, and second I have mesh the volume ( result of substracting the model from a bigger brick ) but the grid doesn't seem to be refined around the model as I wanted. How can I solve my problem? Have you alredy found the answer Jack?

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