[trbprnz]

Hi, I would very much appreciate some help with a meshing problem in Ansys Meshing, to which I am completely new. I am trying to mesh the domain depicted on the left picture (xy-cross-section) as sketched on the right (again, xy-cross-section).
It is a CFD problem where the bottom annular face is the inlet and the top face is the outlet. The annular region needs a fine mesh, which is supposed to get coarser both in the radial and axial direction in the upper tubular part of the domain.
I have so far created three different parts/bodies in Design Modeler and in Meshing I am now trying to implement the following concept:

1. Lower annular part: Combination of a face and sweep feature.
2. Upper annular part: Another sweep with bias in the axial direction such that the mesh gets coarser towards the outlet.
3. Tubular part: Face mesh on the lower conical area with radial bias such that the mesh gets coarser towards the center combined with an axial sweep, which is constrained by the boundaries (mesh of the upper annular part) in order to also get a coarsening towards the outlet.

My questions/issues are:

1. Generally, is the meshing concept reasonable or is there a better/simpler concept I should go for? The limitation here is DM & Meshing though.
2. W.r.t. #2: The bias in the axial direction does not work, the mesh is equally spaced. What am I missing here?
3. W.r.t. #3: The face mesh on the lower conical area is not accepted, the feature is displayed with the forbidden-symbol after meshing. Is it because this face is not a plane? What alternative could I go for in order to get this are meshed with the required coarsening in the axial and radial directions?

Could anyone please provide some hints? Many thanks, best regards, Alex

[Gweher]

Hi Alex,


You can apply bias in the edge direction you want, you can use the edge sizing tool. RMB on Mesh > insert > sizing. Then use the filter selection tool and pick the edges. Then you can specify either the element size or the number of divisions per edge, and use a bias option.



The sweep method needs sometime an additional user input. If it fails you can specify a manual source and target face as well as the default sweep element size.


Regarding the mapped face, the “forbidden” symbol just indicates that this mapped face method is not valid for the geometry you’ve selected. You should always think that a mapped face “needs” 4 different sides (like if you’ve squeezed / deformed an initial rectangle to fit your geometrical boundaries). For instance you cannot apply a mapped face method on a triangular face as you only have 3 edges (in this case you need a quarter o-grid / y-grid approach).


Moreover if you want a radial distribution do not forget that at the axis centre line you’ll end up with degenerated elements (hex with a collapsed edge). So it would be better to use a multizone method with an inflation layer.

[trbprnz]

Hi, many thanks for the hints. Managed to create a reasonable hex mesh w/o the radial refinement, as suggested. Great!