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Divergence in UDF for density case

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Old   February 14, 2022, 02:01
Default Divergence in UDF for density case
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Sai Krishna
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Hi All,
I have to simulate high pressure liquid flow with custom density equation. For this I am trying to validate my UDF approach. I considered ideal gas equation in a UDF and trying to compare the results with available ideal gas method in Fluent. Though UDF is not showing any error in interpretation, but simulation is diverging in no time. Changing the courant number and under relaxation factors just postponed the divergence.
I am attaching UDF and residuals pics of the same. Can anyone let me know what can be the issue in this?

Note: Actual eqn is the one which I need to incorporate finally

Thanks and regards.
Attached Images
File Type: jpg initial error.jpg (79.9 KB, 5 views)
File Type: png udf.png (6.1 KB, 4 views)
File Type: jpg final error.jpg (76.3 KB, 3 views)
File Type: png actual equation.png (68.1 KB, 3 views)
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Old   February 15, 2022, 01:53
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Alexander
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AlexanderZ will become famous soon enoughAlexanderZ will become famous soon enough
check mesh quality
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Old   February 15, 2022, 03:06
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Sai Krishna
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Quote:
Originally Posted by AlexanderZ View Post
check mesh quality
Thanks for the response @Alexander.
I have already simulated ideal gas model on the same mesh and it ran smoothly. Problem arising when Iam considering UDF.
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