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Old   November 13, 2008, 09:15
Default Free Surface Position
  #1
Jennifer
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Hi

I wonder if anyone can help me. I am trying to run a simulation based on a torpedo floating on the surface of the sea. I am not planning on implemeting waves to the calculation yet but it is a thought for the future. My problem is that I cannot seem to get the free surface in the correct position. I have set the CEL Expressions and even run a number of simulations (rough ones) to try and get a picture of where the free surface lies but it is not in the right position (in the middle of the torpedo). Also If anyone can tell me how to upload a picture to a post I can post a couple of pictures to explain what i am talking about more clearly.

Can anyone help with this, How do I move the free surface into the correct position and what boundary condition should I use for the side of the model, i thought opening would be best but I dont know the values to use. I am relatively new to CFX and have not been using it for long.

Many thanks

Jen
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Old   November 14, 2008, 08:08
Default Re: Free Surface Position
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latslosh
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Hi,

Best if you check what your mesh looks like (i.e. how many elements depth-wise) near the free surface - are you using structured or unstructured?

Cheers, latslosh
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Old   November 16, 2008, 17:46
Default Re: Free Surface Position
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Chebeba
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Make shure your mesh is dense around where you expect the surface to be. You should calculate about 4 mesh cells in the precision you want to determine the surface level at.

For example, if you want to calculate the surface level within 10mm, you should have 2-3 mm mesh size in the surface normal direction. Parallel to the surface the mesh can be less dense, that's why structured mesh is usually superior in this application.
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Old   November 17, 2008, 02:51
Default Re: Free Surface Position
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pmp77
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Hello,

here is how to post pictures:

http://www.cfd-online.com/Wiki/Ansys...ible_answer.3F

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