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[ANSYS Meshing] To ask a question about O-grid generation |
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July 11, 2012, 11:40 |
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#21 | |
Senior Member
lnk
Join Date: Feb 2011
Location: Switzerland
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Quote:
If the mesh doesn't follow the geometry, what should I associate the edges at the connection part to? To the circle or the rectangle? I tried both of them but neither of them shows a good result. If I just leave them there without associating, it turns to the result of the picture above (at the previous post) which is same as associating to the rectangle. At this attachment, you can see what if I associate it to the circle. The mesh at some places are missing. Last edited by lnk; July 11, 2012 at 12:16. |
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July 12, 2012, 00:04 |
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#23 |
Super Moderator
Ghazlani M. Ali
Join Date: May 2011
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a little update...
Here is what i tried today: Only one problem: i couldn't do this blocking after i changed the geometry by keeping only the tube and the small box in the middle, i couldn't do it whith the hole geometry. I don't know why... |
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July 12, 2012, 03:53 |
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#24 |
Senior Member
AB
Join Date: Sep 2009
Location: France
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This blocking is nice but doesn't change the fact that the elements at the conection between the circle and the rectangle are very bad. You can't avoid this, unless you change your geometry.
I think what flotus suggested was to redo your geometry by deleting the triangle parts ... because it might not be relevant for your calculation. And then, redo another blocking which would be simpler. Flotus, correct me if I misunderstood you |
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July 12, 2012, 04:03 |
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#25 |
Super Moderator
Alex
Join Date: Jun 2012
Location: Germany
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That is exactly what I meant.
If you give some Information about the flow you want to simulate, then maybe we can figure out how the geometry can be changed without altering the flow field significantly. |
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July 12, 2012, 05:37 |
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#26 |
Super Moderator
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We can modify the blocking in the corner inside the box , but i think there is no option at the two extreme corners where lines have to be tangent to circle.
We can use options: 1) modify the geometry 2. apply tetra meshing in the box surrounding the circular pipe. |
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July 12, 2012, 06:24 |
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#27 | |
Senior Member
lnk
Join Date: Feb 2011
Location: Switzerland
Posts: 118
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Quote:
Best regards and many thanks, lnk |
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July 12, 2012, 10:37 |
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#28 | |
Super Moderator
Ghazlani M. Ali
Join Date: May 2011
Location: Tokyo, Japan
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Quote:
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July 12, 2012, 10:50 |
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#29 |
Senior Member
AB
Join Date: Sep 2009
Location: France
Posts: 323
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It's a quality to be stubborn when you have to deal with blocking
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July 18, 2012, 15:41 |
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#30 |
Senior Member
lnk
Join Date: Feb 2011
Location: Switzerland
Posts: 118
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Hi. Here is the problem we talked about a lot. I'm thinking about why don't we use domain interface to solve this problem? We don't have to make the nodes match at the connection part any more with the domain interface at CFX.
Since I'm fresh to this method, I'm wondering is the domain interface method accurate or not? By this method we can solve every geometry very easily. But life shouldn't be that easy. What's the drawback of the domain interface problem? Best regards, lnk |
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July 18, 2012, 16:30 |
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#31 |
Super Moderator
Alex
Join Date: Jun 2012
Location: Germany
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If you can wait until tomorrow, I can show you a picture which illustrates the drawback of non-conformal interfaces.
The accuracy is poor and the interpolation slows down the solution process. Before adding interfaces, i would rather choose tet or poly meshes. Edit: Here are the results of a simple heat conduction case with nonconformal interfaces. There are three interfaces in X-direction. You can clearly see the discontinuities in the temperature distribution, even when the mesh size on both sides of the interface is similar. Last edited by flotus1; July 19, 2012 at 02:20. |
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July 19, 2012, 04:14 |
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#32 | |
Senior Member
lnk
Join Date: Feb 2011
Location: Switzerland
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Quote:
Thank you very much for your answer. May I ask if the accuracy is always this bad, in what case should we still use it? Best regards and many thanks, lnk |
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July 26, 2012, 04:19 |
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#33 |
Senior Member
lnk
Join Date: Feb 2011
Location: Switzerland
Posts: 118
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Hi
I'd like to test GGI to solve the problem. May I ask which button may I use to unmatch the mesh across the connection part? Best, lnk |
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July 26, 2012, 04:30 |
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#34 |
Super Moderator
Alex
Join Date: Jun 2012
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The two faces of the meshes you are trying to join via an interface have to contain non-conformal nodes.
If the meshes are identical on the two faces, fluent matches the nodes automatically and creates an internal interface. I don't know how to prevent this. So the easiest way is to create meshes with non-matching nodes at the interface. Concerning your first question: as always, it depends on what you are trying to simulate. Non-conformal interfaces are definitely a no-go in a LES for example, but for the steady-state calculation of a global parameter like pressure drop between inlet and outlet the interpolation might be no problem. As you can see, the question cannot be answered universally, so checking the influence for a specific case is definitely a good idea. |
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