# How to transform (mass flow rate) boundary condition from 3D to 2D?

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 October 18, 2012, 03:26 How to transform (mass flow rate) boundary condition from 3D to 2D? #1 New Member   Nurul Join Date: Sep 2012 Posts: 15 Rep Power: 6 Hello everybody, I'm using CFD-Fluent to simulate gasification. In my case, mass flow rate that enter gasifier column is 0,0074 kg/s of coal. I want to simulate with 2D geometry. Only half of the domain with is modeled because of symmetry. Is it same the number of mass flow rate in 3D and 2D? Is the mass flow rate used in 2D unchanged (0,0074 kg/s)? Or the mass flow rate must be devided to transform in 2D? I hope you can help me. Thanks. Last edited by nurul efha; October 18, 2012 at 04:09.

 October 20, 2012, 13:29 #2 Member     Join Date: Mar 2011 Posts: 64 Rep Power: 7 Hi. Are you using 2D Ax-symmetric? If yes, mass flow should be divided by (2*PI). You are just modeling 1 rad of the whole circle. __________________ Saeed Sadeghi Ansys Fluent CFD Consultant

October 21, 2012, 17:59
#3
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misagh
Join Date: Apr 2012
Posts: 63
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Quote:
 Originally Posted by nurul efha Hello everybody, I'm using CFD-Fluent to simulate gasification. In my case, mass flow rate that enter gasifier column is 0,0074 kg/s of coal. I want to simulate with 2D geometry. Only half of the domain with is modeled because of symmetry. Is it same the number of mass flow rate in 3D and 2D? Is the mass flow rate used in 2D unchanged (0,0074 kg/s)? Or the mass flow rate must be devided to transform in 2D? I hope you can help me. Thanks.
HI
You had better use intensive property for your simulation and further calculation.it is an easy way to get rid of changing units in 2.d or 3.d . i mean instead of using mass flow rate(which is an extensive property) just use velocity(intensive property)
good luck

October 21, 2012, 20:47
#4
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Nurul
Join Date: Sep 2012
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Quote:
 Originally Posted by eng_s_sadeghi Hi. Are you using 2D Ax-symmetric? If yes, mass flow should be divided by (2*PI). You are just modeling 1 rad of the whole circle.
I'm using 2D planar...

October 21, 2012, 20:49
#5
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Nurul
Join Date: Sep 2012
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Quote:
 Originally Posted by misagh HI You had better use intensive property for your simulation and further calculation.it is an easy way to get rid of changing units in 2.d or 3.d . i mean instead of using mass flow rate(which is an extensive property) just use velocity(intensive property) good luck

I think so. Thanks...

October 27, 2012, 14:03
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Nick
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Quote:
 Originally Posted by eng_s_sadeghi Hi. Are you using 2D Ax-symmetric? If yes, mass flow should be divided by (2*PI). You are just modeling 1 rad of the whole circle.

Can you expand on this ? I have always entered the full mass flow for axisymetric problems, not a 1 rad slice...

Quick search to find a Fluent manual online, reveals the following, (v6.3)

http://hpce.iitm.ac.in/website/Manua...ug/node227.htm

Quote:
 Note that for axisymmetric problems, this mass flow rate is the flow rate through the entire ( -radian) domain, not through a 1-radian slice.
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July 31, 2016, 19:11
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John
Join Date: Jul 2011
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Quote:
 Originally Posted by Nickul Can you expand on this ? I have always entered the full mass flow for axisymetric problems, not a 1 rad slice... Quick search to find a Fluent manual online, reveals the following, (v6.3) http://hpce.iitm.ac.in/website/Manua...ug/node227.htm
Totally agree with Nickul about Mass flow rate (e.g. for v16.2):
"Note that for axisymmetric problems, this mass flow rate is the flow rate through the entire ( $2\pi$-radian) domain, not through a 1-radian slice."
https://www.sharcnet.ca/Software/Ans...low_Inlet.html

Only Mass Flux is through the 1-radian slice: "mass flux is the flux through a 1-radian slice of the domain."

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