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Problem converting from Tetrahedral to Polyhedral Mesh |
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#1 |
New Member
Iakov Bobrov
Join Date: Mar 2020
Posts: 4
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Hi everyone,
I am trying to run my firts ever 3D simulation in Fluent - over a supersonic rocket, and I would like to ask for help with the following. I understood that I would need to implement polyhedral mesh to save time and cut the cells number to be below 500,000 (uni license). For some reason, I do not always get the polyhedral mesh. Often, surface of the rocket is meshed with the polyhedrals but with the lines inside (or triangles?), see below. pic1.PNG pic2.PNG So this way the number of cells adjacent to the rocket actually increases! I noticed that this does not happen when I get rid of the inflation layer, see below. pic3.png Also, attaching a picture with the tetrahedral cells, before converting them. pic5.png Could someone point to me what am I doing wrong, please? And the second question is, I found it really hard to mesh the nosecone, which is a sharp geometry. And the resultant mesh does not represent the geometry - I thought the reason could be that the mesh is not fine enough. Then, is it simply adding as many cells as possible near the sharp tip? I have tried face sizing and the sphere of influence - are there better strategies? pic4.PNG Or is it not to do with the number of cells? Thank you! Last edited by iakov1703; March 24, 2020 at 14:19. |
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#2 |
Senior Member
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There are two aspects of what you are doing and observing. First, Fluent will NOT convert hexahedral cells to polyhedral. So, if the boundary layer mesh is made of hex cells, those will be maintained as it is. If those are made of triangular prisms, then those will be converted. However, that's where the second aspect comes into play. Since you are looking at the mesh on the surfaces, inflation layer will always show rectangles. You have to mark a few cells near the boundary and then display the register. You can use Adapt > Boundary to mark cells. Do not click on Adapt. Just choose the wall of the nose cone, use 1 or 2 cell distance and then click on Mark. Go to Manage > Display and this will display 3D cells. You may have to enable options for displaying it in 3D under the options. All these are accessible from Adapt > Manage.
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Regards, Vinerm PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority. |
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#3 | |
New Member
Iakov Bobrov
Join Date: Mar 2020
Posts: 4
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Quote:
It seems like in Fluent 2019 the option to Mark cells disappeared and I can't even try it now! pict.PNG Since I am inserting the inflation layer on the surfaces, like you said the boundary layer mesh will be made of hex cells, and therefore I will always see rectangles instead of the polyhedral mesh on the rocket surface. Is that correct, please tell me if I misunderstood you? |
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#4 |
Senior Member
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Cell marking is just to help you in seeing the shape of the cells.
Inflation layers, whether made up of hexahedral or triangular prisms, will only show rectangles on the the surfaces. You have to create a surface of revolution, that is shaped like the object itself but is slightly offset from its surface so that you could display the mesh on this surface. But as you can observe from the mesh on the surface of the object, all faces are polygons implying the inflation layer created in mesh is made up of triangular prisms and not hexahedral cells. If inflation layer would have'd been hexahedral, it would show quadrilaterals on surface of the object. But, as mentioned above, sides are always rectangular.
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Regards, Vinerm PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority. |
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#5 | |
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Iakov Bobrov
Join Date: Mar 2020
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Quote:
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#6 |
New Member
Giuseppe
Join Date: Dec 2021
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Hi, i got the exact same problem for polyhedral mesh. Did you find any solution to that?
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#7 |
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Void_CFD-user
Join Date: Feb 2022
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I'll say, simply use Fluent Meshing, it'll solve all your problems, no need to convert tet to poly if you make a poly to begin with. Will also make it easy to take care of the boundary layer at the cone tip.
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