Learning Forum

[shivam321998]

I've a volume of 2x1(m) which encloses the model below, also the model has same length and width(excluding the cylinder which is of 190mm). I've tried tried three strategies until now i.e split the volume, change element order and assembly meshing. All three have given me Orthogonal quality in powers of -4. I was successful once in achieving acceptable quality but that gave me element statistics of 20 million.

[peteroznewman]

Link to your previous discussion.

Use a big computer and 20 million cells are possible.  This blog describes 3 billion cells.

Did you split the volume to the point of having hex mesh?

[shivam321998]

Yep, I tried splitting the entire volume into 16 parts but hex dominant meshing gives low normalized surface-volume ratio. Multizone and sweep aren't possible on the fluid domain, although I'm able to generate structured meshes for the solid domain.

[peteroznewman]

Never use Hex Dominant meshing on fluid volumes. That is only intended for solids.

Don't say sweep isn't possible on fluid domain. You just didn't slice it into enough pieces.

[shivam321998]

Sweeping works when I slice the body into 16 parts but the overall orthogonal quality reduces significantly as compared to tetrahedral patch-confirming method.

[peteroznewman]

Slice up the geometry where the orthogonal quality of the hex elements was low to improve that. Hex elements are your best option to reduce cell count because you can have larger dimensions in the direction of flow and smaller dimensions across the flow where the velocity gradients are high, without compromising orthogonal quality. You can't do that with a tet element.

[shivam321998]

Alright, I'll give it a try. Although, multizone meshing fails on the volume but I'll try to split the volume from multiple directions.

[peteroznewman]

Mulitzone may fail before slicing, but after slicing, each piece should be sweepable. Right click on Mesh to Show Sweepable Bodies.

[soto6942]

Why do you mention that you never have to use hexagonal dominant meshes in fluid volumes? What problems can you include in the results?

[peteroznewman]

Hex dominant mesh control is listed in the ANSYS help guide as for Mechanical only and must not be used for CFD. The reason is it makes large ugly elements on the interior which are more or less harmless to Structural solvers but deadly to CFD solvers.

[soto6942]

 Sorry to do this, but you could see one of the last posts published and own about meshing, I have some doubts about the subject in CFX and your help would be a salvation