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-   -   UDF DEFINE_UDS_FLUX problem (http://www.cfd-online.com/Forums/fluent-udf/43989-udf-define_uds_flux-problem.html)

Tim March 3, 2007 23:51

UDF DEFINE_UDS_FLUX problem
 
Hi,

I am trying to add a uds equation into my simulation of two phase flow. I define my flux term with DEFINE_UDS_FLUX, the result is awful. I compared the result of default "mass flow rate" and a very simple flux function, which are supposed to yield similar results. But the difference is very big, the UDF even don't converge. Could you please help me out with it?

DEFINE_UDS_FLUX(my_uds_flux,f,t,i) { return F_FLUX(f,t); }

Thank you very much.

Tim

Tim March 4, 2007 14:55

Re: UDF DEFINE_UDS_FLUX problem
 
I am using Fluent 6.3. Here, my uds is hooked to the dispersed phase. I tried it on the continue phase, the "mass flow rate" option and F_FLUX gave consistent results. only when i hook it to the solid phase with the udf difined flux, the computation blow out. Any suggestion will be heartily appreciated.

Tim

Tim March 5, 2007 12:12

Re: UDF DEFINE_UDS_FLUX problem
 
hi, someone told me that to get the right flux, the return value of F_FLUX must time the area of the face. Is it correct, I could not find it in the user guide.

759599290 October 28, 2012 08:56

Hi,Tim
I am checking what does F_FLUX return now. I have noticed that F_FLUX is a scalar rather than a vector. In udf manual of fluent 6.3, there is a paragram that use vec(velocity) dot vec(Face Area) to represent F_FLUX, according to this, it seems that F_FLUX itself returns the value of mass flow rate through the given face, its unit might be kg/s. But when I use the code in the udf mannul to check this idea, i found that F_FLUX(f,tf) is not equal to vec(velocity) dot vec(Face Area). if you get some useful information about F_FLUX, i hope you can share with us.


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