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-   -   udf for an additional source term (http://www.cfd-online.com/Forums/fluent-udf/108708-udf-additional-source-term.html)

bivas108 October 31, 2012 00:37

udf for an additional source term
 
how to define or write an udf for x_momentum source in between two adjacent cells:confused:

skbasak October 31, 2012 00:49

Problem for Y plus in wind turbine analysis
 
Dear All
I am new in this site. I don't know how to post a new issue thats why i am using this reply.

Now I am using k-omega SST model to simulate the vertical axis wind turbine. I did not check the Y+ value before. Now how does it will effect for the wake study (downstream velocity region)?

Is there any particular range that this value should be lie within this range?

Thanks in advance.

davidwilcox October 31, 2012 13:16

Hi Bivas108,
you would first need to create different zones in your mesh. I'm not sure if you used ICEM to create your mesh but you can do it there. Once you have two zones ( in your case, 2 different cells), you can introduce a source term in one cell. There are few examples of udf source terms online that you can refer to but create the two zones first if you want to apply them. Hope this help. :)

davidwilcox October 31, 2012 13:19

Hi Sanjit,
pertaining to your question as to what value the Y+ should be. In most papers, y+ is set to 1. Be careful though, if you were to use the standard wall function in Fluent, any Y plus value below 11.3 ( i think) can deteriorate the solution. Again, it depends on your reynolds number.

skbasak October 31, 2012 13:43

K-omega SST model y+ value
 
In fluent I saw while I use this SST model there is no option for near wall treatment. As this model is a combination of k-epsilon and k-omega model it automatically optimizes the near wall treatment.

I am doing vertical axis wind turbine simulation focusing on wake. As for this concern how important is this to study the near wall treatment?

The Reynolds number I calculated from the blade relative speed is 595304.639. And this is a turbulent flow as found the range for the Reynolds number from at least 10000 to 500000.
http://www.aerodrag.com/Articles/ReynoldsNumber.htm

Any suggestion or comments on this are welcome.

Thanks in advance.


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