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December 11, 2012, 14:40 
Mass Weighted Average

#1 
Member
Brock Lee
Join Date: Sep 2012
Location: Midwest
Posts: 37
Rep Power: 5 
Hey guys, I'm looking to calculate a mass weighted average over a faceZone for pressure using swak4foam. Specifically, this is the equation I'm trying to implement...
Capture.PNG My question comes when trying to implement. Is it possible in swak4foam to divide a sum by a sum within one expression? Can I do two sums separately and divide them? So far I've only seen expressions that can do one accumulation, such as the one below for mass flow rate... Code:
massin { type swakExpression; valueType faceZone; zoneName interiorinlet1; expression "phi*flip()"; accumulations ( sum ); verbose true; autoInterpolate true; } 

December 11, 2012, 18:32 

#2 
Member
Brock Lee
Join Date: Sep 2012
Location: Midwest
Posts: 37
Rep Power: 5 
Ok, I think I found an equivalent expression. The following function I believe does what I need it to do...
Code:
p_stat2 { type swakExpression; valueType faceZone; zoneName interiorinlet1; expression "(p*phi*flip())/sum(phi*flip())"; accumulations ( sum ); verbose true; autoInterpolate true; } Also, does anyone know if when you have backflow on a face, does it register as negative mass flow using the phi*flip() formulation? Last edited by GRAUPS; December 12, 2012 at 13:37. 

December 12, 2012, 19:48 

#3  
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Bernhard Gschaider
Join Date: Mar 2009
Posts: 3,915
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Quote:
Yes. You should get the correct backflow if you use flip() (the sign of phi depends on the orientation of the face. Multiplying with flip() "removes" that dependence)
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December 12, 2012, 20:34 

#4  
Member
Brock Lee
Join Date: Sep 2012
Location: Midwest
Posts: 37
Rep Power: 5 
Quote:
Fantastic, just wanted to make sure. Thanks for your replies. 

Tags 
mass weighted average, swak4foam, swakexpression 
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