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Mesh Generation-negative voulumes

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Old   April 30, 2005, 20:52
Default Mesh Generation-negative voulumes
  #1
Rajesh G
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I am ending up with negative volumes when the grid is checked using Fluent 6.1. The grid has been generated for a blunt cone using Gambit. The negative volumes appear in the curved portion of the blunt cone. When I increase the no, of nodes the negative volumes are seen to be decreasing. But not disappearing. It would be a great help to me if somebody can suggest a solution for this problem.

Thanking you Rajesh
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Old   May 2, 2005, 22:32
Default Re: Mesh Generation-negative voulumes
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pah
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Hi

I met your prolem and it is colved by increase the No of nodes, especially at the place curve is hight level. Maybe, there are some other solutions but I just know one. Hope it is useful for you.

PAH
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Old   May 2, 2005, 22:38
Default Re: Mesh Generation-negative voulumes
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Rajesh G
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Thank u for ur suggestion. But I can't increase the no of nodes beyond a particular limit as that will affect nodes created in other faces. Is there anything wrong with the creation of the curved edge?

Rajesh
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Old   May 2, 2005, 22:46
Default Re: Mesh Generation-negative voulumes
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pah
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I think, you should control No of node from each edge espicially at the important curves and where is curved egde, then with the faces. I'm beginer in Gambit and Fluent, so I don't have so many experience. I hope usefull for you.

PAH
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Old   May 3, 2005, 08:04
Default Re: Mesh Generation-negative voulumes
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Jason
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It depends on the curvature of the face. A common problem is the tip of a cone... no matter how small the mesh is, there's still a point with a fixed angle, and the mesh can "collapse" in on itself at the tip and create negative volumes. A common way of dealing with this is to split the face in an appropriate way to control the mesh and prevent it from collapsing. This can happen in other curved surfaces as well (the cone was just an easy example). The key is to look at the geometry and try to picture what you want the mesh to look like in the area that's giving you a problem. Once you know what you want it to look like, start splitting the edges and faces to get the appropriate results. If you send me images of your geometry (especially in the problem area) I can try to help.

Goodluck, Jason
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Old   May 5, 2005, 01:11
Default Re: Mesh Generation-negative voulumes
  #6
Rajesh G
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Thank you very much for your prompt reply. Now I can try generating a fresh geometry based on your advice. Actually I have tried spliting the curved space. But it gives more total numebr of nodes in the edge if the edge is divided more. That makes the solution much time consuming and it needs more computational capacity also. Anyway I can try for a compromise between the number of nodes and the time. If that doesnot solve the problem, I will contact to you with the geometry.

Thank you very much.

Rajesh
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