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April 12, 2014, 02:30 |
UDF for turbulence model implementation
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#1 |
Member
Luca
Join Date: Mar 2011
Location: Italy
Posts: 62
Rep Power: 15 |
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. |
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July 10, 2017, 18:12 |
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#2 |
Member
Vedamt Chittlangia
Join Date: Feb 2016
Posts: 64
Rep Power: 9 |
Hello Luca,
Though this is an old post but were you able to get the solution to the problem. I face similar issue with AKN model. Thanks |
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turbulence modeling, udf, uds |
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