[ykj5467]

I have meshed and ran a simulation of a jet into a quiescent fluid. The simulation diverged, and I've gone back to try and improve the mesh. I have some skewed elements close to the inlet patch that have been identified using ICEM check mesh.

Attached is a picture of the circular inlet, and the front wall patch. They are both located at x = 0. I would like to add circular rings/inflation layers around the inlet outer edge because that is where skewed elements were identified. I am hoping that improving the surface mesh will lead to better volume meshing close to the inlet, especially in the shear layers.

Any help greatly appreciated.

P.S. I am meshing with unstructured elements because this is a simple test case that'll become more complex and require unstructured meshing.

[Gert-Jan]

I don't understand the problem. Please share a view from the internal mesh.

[ykj5467]

Originally Posted by Gert-Jan

I don't understand the problem. Please share a view from the internal mesh.

Attached is a view of the internal fluid volume mesh from along the mid-plane. The flow is from right to left. You can see 3 inflation layers coming from the orifice (inlet). This mesh is actually stable when ran with adaptive time step and CFL<1, however dt = 1e-5 and therefore it is very slow to run.

I am not happy with the elements near the orifice, but I don't know how to improve them.

I thought improving the surface meshing of the orifice would lead to better cells in the fluid. That is what I was addressing in my original post. If I add prism layers to the orifice, it meshes inflation layers inside the fluid, not around the orifice perimeter (to be expected). Seems a little strange to mesh prism layers into the fluid from an inlet.

[Gert-Jan]

Normally inflation is applied on walls, not on inlets, outlets or interfaces.
In your case you appear to only apply inflation on the inlet of the pipe. Then why not also on the surfaces parallel? Then the mesh will improve.

[ykj5467]

Originally Posted by Gert-Jan

Normally inflation is applied on walls, not on inlets, outlets or interfaces.
In your case you appear to only apply inflation on the inlet of the pipe. Then why not also on the surfaces parallel? Then the mesh will improve.

Thanks for the rapid reply.

I had applied inflation layers to the whole surface surrounding the orifice. This lead to a huge mesh, and at this stage I am looking to test a course mesh before refinement. I can however split the wall patch up and apply inflation layers around a smaller 2D plane surrounding the orifice.

I realise it's more common to apply inflation layers to a wall to resolve large gradients, but I also need refinement close to my inlet, so is it valid to have inflation layers adjacent to an inlet?

Also, could the surface mesh of the orifice be improved?

[Gert-Jan]

In your case I would apply inflation all over. Or at least to a limited extent over the parallel surface, to reduce numer of elelements. Alternatively you set less layers (1?) on the large surface away from the inlet.