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March 1, 2010, 05:09 
calcMassFlow problems

#1 
Member
Jérémy Bulle
Join Date: Nov 2009
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Hello,
I'm trying to use the "calcMassFlow" utility but I have some questions :  Currently, he calculates the massflow every 50 timestep but my case only writes data every 500 timestep. How to change this for calcMassFlow so that it calculates the massflow every 500 timestep instead of 50?  The massflow is exactly 2 times the massflow fluent calculates for the same case (1.34 wheras it should be 0.67). I've made a third dimension of 1 meter because fluents uses a 3rd dimension of 1 meter to calculate its massflow. Where is my problem? Thanks a lot for the help 

March 1, 2010, 10:20 

#2  
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Bernhard Gschaider
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Quote:
That utility can only work with written timesteps, so I'm a bit amazed that you get output more often About the factor 2: you're not by any chance using an incompressible solver and the density of your fluid is 0.5? The other suspect is that in the dictionary you've got a scaleFactor 2 (because of reusing that from a symmetric case for instance). Bernhard 

March 1, 2010, 13:37 

#3 
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Jérémy Bulle
Join Date: Nov 2009
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Yep that's this utility
About the rho, I set it to 1.2 for air About the scale it's commented So I don't understand why I get such results ... 

March 2, 2010, 13:59 

#4 
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Bernhard Gschaider
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March 2, 2010, 14:11 

#5 
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Jérémy Bulle
Join Date: Nov 2009
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Well I don't see where I could have go wrong ...


March 2, 2010, 15:47 

#6 
Assistant Moderator
Bernhard Gschaider
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Me neither (because I don't know the case). One thing you try is to use foamDataToFluent (see UserGuide) to get data into Fluent and check whether the you get the expected value or the calcMassFlowvalue there Bernhard


March 2, 2010, 16:41 

#7 
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Jérémy Bulle
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Oh I'll try this!
Thank you! 

March 2, 2010, 17:00 

#8 
Member
Jérémy Bulle
Join Date: Nov 2009
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I tried this and I get 0 in fluent so this must be a problem in the conversion.
I made "foamDataToFluent" and "foamMeshTofluent" then I select fluent3ddp and tried to do report> fluxes > massflow but that doesn't work ... Normaly it's a 2D case but apparently when I select 2ddp this doesn't work since openfoam works with 3D meshes and specific boundary conditions. Maybe it's because of that ... ? 

March 3, 2010, 10:45 

#9  
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Bernhard Gschaider
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Quote:
Bernhard 

March 23, 2010, 05:21 

#10 
Member
Jérémy Bulle
Join Date: Nov 2009
Posts: 93
Rep Power: 9 
Now that I've made my case 3D, I no more have any problem ... Something had to be wrong with the 2D case, yet I paid attention to the third dimension ...


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