pressure outlet BC for turbulence parameters

alinik · June 23, 2017, 12:18

Hi all,

I am re-writing k-omega turbulence model using UDF (UDS) and have achieved limited success.
The problem is I am not sure what kind of boundary condition do I have to set for transported quantities (k and omega) at the outlet location?

Any kind of help is much appreciated.

Thanks,
Ali

vcvedant · July 12, 2017, 14:23

Hi Ali,

You can define flux as zero for both k and omega at the outlet. You should define outlet as "pressure outlet".
I am writing UDF for low-Reynolds model but my solution always diverges, can you send me your code that would be really helpful. My email is: cfdmaster2017@gmail.com

Thanks,
Vedant

pachi · July 23, 2017, 11:17

Hii vcvedant,

am working on fluid structure interaction in the flexible pipe..

FSI is working for low magnitude of pressure (0 to 12Pa) UDF boundary condition in the fluent. however when i define higher pressure in the UDF file FSI fails to work.

Getting error like..

1) "Update failed for the Solution component in System Coupling. The coupled update for System, Fluid Flow (Fluent), threw an exception".

2) "System coupling run completed with errors. Transient Structural (Solution 1) reported: One or more elements have become highly distorted. Excessive distortion of elements is usually a symptom indicating the need for corrective action elsewhere. Try ramping the load up instead of step applying the load (KBC,1). Please do not save the project if you would like to recover to the last saved state".

Thank You

June 23, 2017, 12:18	pressure outlet BC for turbulence parameters	#1
alinik Senior Member ali Join Date: Oct 2009 Posts: 318 Rep Power: 17	Hi all, I am re-writing k-omega turbulence model using UDF (UDS) and have achieved limited success. The problem is I am not sure what kind of boundary condition do I have to set for transported quantities (k and omega) at the outlet location? Any kind of help is much appreciated. Thanks, Ali

July 12, 2017, 14:23		#2
vcvedant Member Vedamt Chittlangia Join Date: Feb 2016 Posts: 64 Rep Power: 9	Hi Ali, You can define flux as zero for both k and omega at the outlet. You should define outlet as "pressure outlet". I am writing UDF for low-Reynolds model but my solution always diverges, can you send me your code that would be really helpful. My email is: cfdmaster2017@gmail.com Thanks, Vedant pachi likes this.

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July 23, 2017, 11:17		#3
pachi New Member Prashanth Join Date: Jun 2016 Posts: 20 Rep Power: 9	Hii vcvedant, am working on fluid structure interaction in the flexible pipe.. FSI is working for low magnitude of pressure (0 to 12Pa) UDF boundary condition in the fluent. however when i define higher pressure in the UDF file FSI fails to work. Getting error like.. 1) "Update failed for the Solution component in System Coupling. The coupled update for System, Fluid Flow (Fluent), threw an exception". 2) "System coupling run completed with errors. Transient Structural (Solution 1) reported: One or more elements have become highly distorted. Excessive distortion of elements is usually a symptom indicating the need for corrective action elsewhere. Try ramping the load up instead of step applying the load (KBC,1). Please do not save the project if you would like to recover to the last saved state". Thank You