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About how to apply boundary conditions read from a file

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Old   December 15, 2013, 20:48
Question About how to apply boundary conditions read from a file
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Sang-jin Lee
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Hi everyone
I'm a novice Fluent user but have to do something impressive with Fluent UDF.

What I have to do is FSI analysis with Fluent. I have developed a customized structure solver which works with Fluent by exchanging boundary conditions.

Given a fluid model, after finishing Fluent analysis new force values of nodes on a given surface(FSI surface) should be extracted(node id, coordinates and force value for each node) and saved in a text file and then, structure solver starts to solve with the new force conditions and generates new displacement and velocity conditions for the same surface and saves them in a text file. Fluent, in turn, reads the file and apply them on the surface and starts to analyze to generate new force conditions. (I heard that in this case dynamic mesh should be applied.)

This is what I have to do. I've finished developing structure solver but stopped at interacting with Fluent. I want to get some UDF examples for extracting forces on each nodes to a file and applying displacement and velocity conditions for each node from a file. Can you give me comments or advices for the issue?
I'm lost and don't know where I should go.

Any comments or advices will be appreciated.
Thank you.

Last edited by sangjin lee; December 16, 2013 at 03:27.
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Old   January 14, 2014, 06:57
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Andrew Hallow
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Quote:
Originally Posted by sangjin lee View Post
Hi everyone
I'm a novice Fluent user but have to do something impressive with Fluent UDF.

What I have to do is FSI analysis with Fluent. I have developed a customized structure solver which works with Fluent by exchanging boundary conditions.

Given a fluid model, after finishing Fluent analysis new force values of nodes on a given surface(FSI surface) should be extracted(node id, coordinates and force value for each node) and saved in a text file and then, structure solver starts to solve with the new force conditions and generates new displacement and velocity conditions for the same surface and saves them in a text file. Fluent, in turn, reads the file and apply them on the surface and starts to analyze to generate new force conditions. (I heard that in this case dynamic mesh should be applied.)

This is what I have to do. I've finished developing structure solver but stopped at interacting with Fluent. I want to get some UDF examples for extracting forces on each nodes to a file and applying displacement and velocity conditions for each node from a file. Can you give me comments or advices for the issue?
I'm lost and don't know where I should go.

Any comments or advices will be appreciated.
Thank you.
First of all, in Fluent, you can only obtain forces on faces (via pressure and directed face area). Thus, if you need the resultant force at a node on a surface, then you should loop over each adjacent face of that node, get the face force, and finally average them out.

That done, you can loop over all nodes of the surface, and write the following information to a file: node id (integer), resultant force (3 x real), current coordinates (3 x real). That information can then be readily passed on to the structural solver for a FEM solution of the displacement.

That should get you started. Let me know how it goes!
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