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All're symmetrical , but fluid is not symmetrical ? |
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April 21, 2009, 22:38 |
All're symmetrical , but fluid is not symmetrical ?
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#1 |
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lee
Join Date: Apr 2009
Posts: 6
Rep Power: 16 |
Hello , guys !
I've got a weird question : My model is totally axial symmetrical , other info. : Incompressible ideal gas , gravity enabled , and flow direction is opposite towards the gracity . and after my enabling energy equation , starting calculation , converged , the result shows that the fluid vetor is not symmetrical ! The only asymmetry is the grid , will it affect the result ? What more , when species transport model enabled , the fluid looks more symmetrical , and easier to converge , then what's the effection of s-t model ? Thanks for any help ! Regards ! |
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April 22, 2009, 01:35 |
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#2 |
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Maxime Perelli
Join Date: Mar 2009
Location: Switzerland
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Basically, if your domain is symmetric and also your BC... depending on the flowfield properties (Re, etc...) it is possible that the fluid doesn't flow symmetrical.
The von Karman vortex are a good example
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April 22, 2009, 09:11 |
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#3 |
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Andrew
Join Date: Mar 2009
Location: Washington, DC
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Did you try refining your mesh or doing a grid check? - maybe your mesh is too coarse
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April 23, 2009, 00:06 |
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#4 | |
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lee
Join Date: Apr 2009
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Quote:
Actually I've tried laminar , k-e , S-A , and it looks turbulence model is better , despite the velocity is low, and Re is between laminar vs turbulence . So would it poosible caused by turbulence model ? And what's more I'm using Incompressible ideal gas model , which is sensitive with high temperature , and the temperature in my case is more than 1000C , so is there some better density model for this ? Thanks again ! lee |
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April 23, 2009, 00:16 |
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#5 | |
New Member
lee
Join Date: Apr 2009
Posts: 6
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Quote:
I think the mesh is fine enough , and grid check is done . Actually the geometry model is simple , what I'm curious is whether the grid really affect symmetry ? What more , if energy equation is not enabled , the fluid is symmetric depending on the same mesh , so I doubt maybe there's a thing on temperature . well , thanks again ! lee |
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April 23, 2009, 02:07 |
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#6 |
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Maxime Perelli
Join Date: Mar 2009
Location: Switzerland
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If you think that it's linked to the mesh, you can split your model on the symmetry plane, and mesh the splitted domain.
Then copy this volume, with reflect and mesh option. Connect the symmetry planes (which should be superposed). Finally you get your full domain, but with symmetric mesh. Re-compute and check if the solution is symmetric or not
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In memory of my friend Hervé: CFD engineer & freerider |
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April 23, 2009, 02:53 |
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#7 | |
New Member
lee
Join Date: Apr 2009
Posts: 6
Rep Power: 16 |
Quote:
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April 23, 2009, 03:02 |
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#8 |
New Member
lee
Join Date: Apr 2009
Posts: 6
Rep Power: 16 |
Further more , is there a proper density model for gas under high temperature ?
Thanks very much ! lee |
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