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July 29, 2013, 04:50 
UDF : heat source located in a solid

#1 
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Hello,
I am an user of FINE/Open. I would like to make a comparison with Fluent. Therefore, I need a little help in Fluent. In my domain, I have a fluid part and a solid part. In the solid, I'd like inserting a localized heat source in function of x, y and z. Is it possible? (and in the definition of the coordinates, it slightly exceeds? eg, due to an imprecise geometry, my xcoordinate exceeds of 1 mm, how Fluent work?) You can help me to construct the udf ? if I have this coordonates for the heat source :  x : x=0 to 0.001  y : y=0 to 0.0015  z : z=0.001 to 0.00012 vol=0.001*0.0015*0.0002; HS=10/vol; thanks a lot ! 

July 29, 2013, 10:59 

#2  
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Alex
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Yes, defining a local heat source via UDF is possible. Here is part of a UDF I used for a similar purpose:
Code:
#include "udf.h" DEFINE_SOURCE(sourceterm,c,t,dS,eqn) { real x[ND_ND]; //some variable declaration real source; C_CENTROID(x,c,t); //reads the position of the cell centroid and writes it to the field x source = 1.0 //instead of the constant heat source, apply whatever function f(x[0],x[1]x[2],...) you need return source; //returns the value of the heatsource for the cell } The DEFINE_SOURCE macro used here loops automatically over all cells in the domain. Consequently, the source term is applied cellwise which means it has a conatant value in a cell. I am sure you can work out the exact function using a few ifstatements. x[0] holds the xcoordinate, x[1] the ycoordinate and x[2] the zcoordinate of the cell centroid. Edit: Quote:


July 30, 2013, 04:08 

#3 
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Thank you ! The code is correct like this? (indeed, I made little mistake for the z coordinate)
#include "udf.h" DEFINE_SOURCE(sourceterm,c,t,dS,eqn) { real x[ND_ND]; real source; real vol; C_CENTROID(x,c,t); if(x[0]=>0 && x[0]<=0.001 && x[1]=>0 && x[1]<=0.0015 && x[2]=>0.001 && x[2]<=0.0012) { vol=0.001*0.0015*0.0002; source=10/vol; } else { source=0; } return source; } 

July 30, 2013, 05:21 

#4 
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Alex
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Looks fine.


July 30, 2013, 07:55 

#5 
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It's strange, I have no warning in the compilation, but the temperature in the solid doesn't increase. An idea?


July 30, 2013, 08:22 

#6  
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Alex
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Quote:
Simply interpreting the UDF does not acrivate any source terms. source_term.jpg 

July 30, 2013, 08:27 

#7 
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Yes yes, I find the error. I was stupid, I made a mistake in one of the coordinates. Thank you for your help !


October 8, 2013, 18:56 

#8 
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David Aliaga
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Hey hi! i have the same problem, i need to put on mi domain a constant heat, momentum and mass source on a localized point on the cell zone ( in this case water liquid). Cause of the options of Fluent it self only allows to loop the source on all the fluid cell zone, i realized that i haved to find the way to program with UDF to indicate just a certain point, in this case the centroid of the cell. I also intempted to make two bodies and assign the fluid zone to both, but the all turns real messy with the zones that are created. My question is, this udf will help me with my problem? wich are the steps for writing my udf. IŽll really appreciated your help =D


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