[mickyB]

Hi all,

I've generated a mesh for a wing in ICEM but when I try to run it in CFX an error code 1 is given. The error code says that at least one negative volume element exists in the mesh and gives me the location of this element. So, back in ICEM I've checked out where these negative volume elements are; they're near the interface between two blocks as shown in the picture attached ("Negative volume elements"). ICEM says there are 17 negative volume elements, but 4 of them can be fixed, resulting in 13 left. The blocking pic is also attached.

These negative volume elements only appear when I set the first element layer of the block adjacent to the wingtip less than about 1.2e-5. The first element height needs to be about 5e-6 for the YPlus to be less than one on the wingtip surface. So, I've tried merging any possible double vertices on the interface between the two blocks, re-associate vertices to points and edges to curves, but neither of these methods have worked.

The strange thing is that I've modeled another wing, which is almost identical to this one and the mesh was fine. I thought that I followed the same method for mesh to this wing...

Does anyone have any ideas about what else I can try?

The element qualities of these negative volume elements are about -0.002 so would smoothing be worth checking out? I'm not that familiar with the pros and cons of smoothing. Alternatively, I thought of perhaps splitting the blocks to create a small block around the wingtip to apply the necessary boundary layer suitable elements and leave the elements further away from the wingtip fairly coarse, but I would really prefer to have the same general mesh as the other wing, for comparison's sake.

Thanks,
mickyB

[Far]

where you see the negative element in ICEM CFD? It may be orientation problem and can corrected by providing the correct jacobains

[mickyB]

Thanks for the reply.

The negative volume elements can be seen in the first figure, that shows the mesh. They appear as a few grey elements near the curved surface. These elements occur very close to the interface between two blocks that cover the curved surface (which is the inlet).

Is it possible to manually input something like a Jacobian for a give element?

[Far]

Originally Posted by mickyB

Thanks for the reply.

The negative volume elements can be seen in the first figure, that shows the mesh. They appear as a few grey elements near the curved surface. These elements occur very close to the interface between two blocks that cover the curved surface (which is the inlet).

Is it possible to manually input something like a Jacobian for a give element?

Yes. see this :

[mickyB]

Okay thanks for your help. I've managed to fix the negative volume problem. I did end up prescribing some element parameters, but I also used the smoothing tool.