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Old   March 12, 2009, 04:39
Default wall has no effect
  #1
Vu, Ha-Hai
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Hi,

I'm trying to do a simple 3D analysis. The flow through a tube with an obstacle inside.

The model includes: Inlet (mass-flow inlet), outlet (outflow), interior1 (tube interior), interior2 (obstacle), tube volume (water), obstacle volume(water), tube wall, obstacle wall.

The solution gets convergence after around 600 iterations. The pressure distribution seems so good.

However, the obstacle has no effect on the flow. (I have done analysis with or without obstacle, the results are the same).

If you guys know the solution, please let me know.

Thanks in advanced.

Vu, Ha-Hai

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Old   March 12, 2009, 10:26
Default Re: wall has no effect
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Jason
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Sounds like a problem with your geometry setup. First two guesses are that you either didn't define the obstacle wall as an actual wall when you wanted to enable the obstacle, or that you didn't setup your volumes properly so that the obstacle volume isn't actually part of the domain.

How did you create your geometry?

Jason
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Old   March 12, 2009, 21:12
Default Re: wall has no effect
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Vu, Ha-Hai
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Hi Jason,

Thanks for your reply.

The geometry has been created through 2 steps: + By using solidworks: Tube and obstacle were created separately, then assembled together by Mate function of Solidworks. The model was saved as in iges format. + By using Gambit: The iges file was imported to Gambit to mesh and setup boundary conditions. There were 2 volumes existing include volume of tube and obstacle. I set them as fluid.

The mesh file was exported to Fluent successfully.

Hai
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Old   March 13, 2009, 14:02
Default Re: wall has no effect
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Jason
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I get that there was two volumes, but the question is if you defined the volumes properly. It should be setup so that if you delete the obstacle volume there will be a large hole in the tube volume where the obstacle used to be.

If this is what happens, then the easiest thing is to delete the volume related to the obstacle and analyze this geometry, rather than having to worry about having your boundary conditions setup correctly to leave the solid mesh of the obstacle.

If this is not what happens then you need to split the tube volume with the obstacle volume. My guess is that this is what's wrong. The two meshes are sharing the same space (the coordinates of the obstacle lay within the domain of the tube), but without having the tube volume split by the obstacle volume, Gambit and Fluent don't know that the obstacle mesh is supposed to influence the tube mesh.

Good luck Jason
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Old   March 13, 2009, 20:36
Default Re: wall has no effect
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Vu, Ha-Hai
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Hi Jason.

Thanks so much for your suggestion. According to your idea, my problem seems to be solved.

Thanks again.

Hai
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