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July 21, 2011, 16:43 
changing a variable (turbulence dissipation rate) formolation

#1 
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Join Date: Nov 2010
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Hi
I must modify eps (C_D) in one part of my work. I simulating a slurry bubble column and I have to modify my turbulence dissipation rate by this formula: eps(modify)=eps(original)*exp(A*alpha) eps(modify):turbulence dissipation rate that I need to use in my calculations eps(original): turbulence dissipation rate that fluent calculates A: constant alpha: volume fraction of particles and I need to change eps to these formula just in my population balance aggregation and breakage kernels. can I do this with a udf? which macro I must use? I know that I can wrote the kernels in udf and hook them to populaton balance model but I want to just change the eps it is more easily and I can use the original code of fluent that have less problems thank you 

July 22, 2011, 03:50 

#3 
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Hi
Thank you amir but I am new in writing UFD, an I have an other question. I want to change eps just in one of fluent parts, and I don't want to write a udf for whole part. you see: for example in population balance model I choose lou aggregation equations that is avalable in fluent just by using population balance model and choose lou kernel for it from a drop down list. but I want to send my eps(modify)" that I wrote the equation of that on the last post" instead of eps(original) to the part of lou equations. I know how to save the my eps(modify) in a UDM, after that how I can send it to the lou equations instead of eps(original) ( that I think using the C_D macro for that in the fluent ) in other word, I want to change or modify one of the fluent equations, is this possible? or I must write whole part of the equation again in a UDF? excuse me for my poor English 

July 22, 2011, 08:23 

#4 
Senior Member

Hi,
I haven't used this model before and I don't know about its characteristics, but I have some suggestions:  first look for capability of hooking any UDF in your desired model description.  I think it would be possible to change C_D for using in this eq. and then retrieving previous value (because I don't know about this model, I'm not sure about)  If you can interpret this model as a conservation eq., then you can use UDS template of FLUENT instead. (again I'm not sure about its nature) Amir 

March 28, 2014, 09:31 
modified dissipation term in kw SST

#5 
Member
Ali.E
Join Date: Sep 2010
Location: Lisboa
Posts: 82
Rep Power: 8 
Hello all,
I want to modify the dissipation term of kequation by UDF. Which macro can be used? Actually, I must change the formulation of dissipation term in kequation and then, Fluent uses the modified dissipation term instead of itselfs. My turbulence model is kw SST and I just manipulate Y_k (dissipation term of k). Original: Y_k=ro*beta_s*k*w; Modified: Y_k=ro*beta_s*k*w/delta; (delta is wall distance) It would be appriciated if anyone makes a comment to how I do this task. 

November 4, 2016, 15:50 

#6  
Senior Member
ali
Join Date: Oct 2009
Posts: 213
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Hi,
Did you find a solution to this problem that you had? Quote:


November 7, 2016, 06:53 

#7 
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Ali.E
Join Date: Sep 2010
Location: Lisboa
Posts: 82
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