[Adithya_11]

Hello
I am generating meshes around an airplane for simulating on Fluent.
My coarse meshes work well.
When I refine the mesh I get pyramid elements in my inflation layers along with the warning of the stair step.

Why do pyramidal elements form? I don't know if I need to refine the surface face sizing or the inflation properties. I have defined the first cell height and inserted x layers.

Could someone tell me why these elements form and how do i get rid of them?

[kjetil]

Pyramid cells do not exist in inflation layers. A single face in a inflation cell can be triangular, but the chape of the cell is extruded so to say.


Is this consistent for the entire structure, or did you leave out certain surfaces by mistake from the named selection?

[siw]

You do not say which meshing application you are using (Fluent Meshing, ANSYS Meshing, SpaceClaim Interactive Meshing, ICEM CFD).

Let's assume you are using ANSYS Meshing. When you select Fluent as the Solver Preference then the advanced inflation layer option Collison Avoidance = Layer Compression (the alternative is Solver Preference = CFX and Collison Avoidance = Stair Stepping).

Pyramids are used to bridge the gap between prisms and tetrahedra when the adjacent columns of prisms do not have the same amount of prism elements, because the side face of a prism is rectangular (4 edges) and the top of a prism and all tetrahedral faces is triangular (3 edges)so the only element that has both triangular and rectangular faces is a pyramid.

[Adithya_11]

Dear kjetil
I get the pyramid elements when I preview only the inflation layers on ANSYS Meshing. I also get some tet elements. Are these elements not in the inflation layers but just visible in the preview?

Thank you for your reply Stuart.
Yes, I am using ANSYS Meshing. I unedrstand the options available and I have layer compression chosen. I still get stairs along with the formation of pyramidal elements. When I refine the area, I get more pyramidal elements.
A better question would be, ' can I proceed with pyramidal elements to Fluent or do I only need tet and wedge?'
I find some answers on the internet that pyramidal elements are not favourable elements to be used in CFD. Is this correct?

[siw]

Fluent will accept pyramid elements. I suggest go with your mesh and do an initial simulation to get a result and investigate if the flowfield in the region of the pyramid elements is not to your liking. Pyrmid elements are just a 'filler' element between the prisms and tetrahedra, so there is probably not many relative the total mesh element quantity. But if you really want zero pyramid elements then experiment with the other advanced inflation layer options (Maximum Height over Base, Maximum Angle etc.) all detailed the Meshing User Guide.

[Adithya_11]

Thank you for your help and reply