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-   -   Free Surface Position (http://www.cfd-online.com/Forums/cfx/26653-free-surface-position.html)

 Jennifer November 13, 2008 09:15

Free Surface Position

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

 latslosh November 14, 2008 08:08

Re: Free Surface Position

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

 Chebeba November 16, 2008 17:46

Re: Free Surface Position

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.

 pmp77 November 17, 2008 02:51

Re: Free Surface Position

Hello,

here is how to post pictures: