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Negative volume in mesh due to contact

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Old   September 9, 2015, 15:28
Default Negative volume in mesh due to contact
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Ahmed Jalal
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I am simulating a ball inside a valve that its motion is determined by a UDF.

When the ball gets close to the wall I get errors about negative volumes. I tried refining the mesh, decreasing the time step, improving Flow Courant Number and relaxation factors. Also, I added the contact detection specifying the boundaries but I still get the same error.

Do I need to compile a UDF for the contact detection?

If so, any advice or push in the right direction would be appreciated.

Thanks
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Old   April 4, 2017, 12:50
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saurabh kumar gupta
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Hi Ahmad,
I hope you have found solution for your problem. i am new to contact detection. as i can see in contact detection you have to specify zones where possibly can happen.

in my case there are two rigid body which are rotating about their own hinge point and in opposite direction. and i need to restrict their motion between 0-55 degree. so would you guide me how can i make this setting and how to write udf for this case.

Regards
Saurabh
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Old   April 4, 2017, 18:00
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Ahmed Jalal
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Saurbah,

I actually switched to Star CCM+, which made my life much simpler when it came to contacts and rigid body motion.

I am not sure about the UDF to restrict the angle. I am sure it is a simple code but I am not an expert in it.

Good luck
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Old   April 4, 2017, 18:29
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saurabh kumar gupta
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Thanks for reply, I will be thankful if you can provide whatever information you have regarding contact detection. Because I am not getting any.
Is it possible to do 6DOF simulation in star CCM+.
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Old   April 4, 2017, 19:24
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Ahmed Jalal
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Yes and it is very simple. There are multiple modules to show how to set it up if you do a quick search.

Mainly through DFBI (Dynamic Free Body Motion) and Overset Mesh.
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contact detection, dynamic mesh, negative volume error, udf

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