CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > FLUENT

UDF for turbulence model implementation

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   April 12, 2014, 02:30
Exclamation UDF for turbulence model implementation
  #1
Member
 
Luca
Join Date: Mar 2011
Location: Germany
Posts: 38
Rep Power: 6
marluc is on a distinguished road
Hallo,

I have just written a UDF for the AKN model (Abe-Kondoh-Nagano).
I tested it for a channel flow, a backward facing step and a ribbed duct.
Upon reaching a convergent solution with a k-e model with enhanced wall treatment I switch off the calculation of the turbulence transport equations and, after initialization of the UDS, I solve for their transport equations, in order to compute the user-defined turbulent viscosity to use in the momentum equations.

My problem is when I first start with the UDS because I often get AMG solver divergence at the first iteration. So I first set the URF to very low values and solve for each UDS separately and without the momentum equations activated. Then I start increasing the URF and later I activate the flow calculation as well.

I am wondering if someone has the same problem when dealing with UDS for a user defined turbulence model.
Furthermore, when using the AKN model implemented in Fluent I can keep the default URF for momentum, k and e and the calculation converges. Does someone have an explanation for this? (actually Fluent and I should solve the same equations!)

Thank you in advance for your answers.
L.
marluc is offline   Reply With Quote

Reply

Tags
turbulence modeling, udf, uds

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
UDF VOF model on Fluent baechtel Fluent UDF and Scheme Programming 6 February 19, 2013 01:56
Water subcooled boiling Attesz CFX 7 January 5, 2013 04:32
Problem with udf radiation model in 2d combustion model..???? shshiva17 FLUENT 0 July 28, 2009 09:44
UDF for Herschel-Bulkely model emad Fluent UDF and Scheme Programming 5 July 20, 2009 08:16
Real gas model with UDF Ed FLUENT 4 September 18, 2003 10:42


All times are GMT -4. The time now is 11:55.