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-   -   How to transform (mass flow rate) boundary condition from 3D to 2D? (https://www.cfd-online.com/Forums/fluent/108251-how-transform-mass-flow-rate-boundary-condition-3d-2d.html)

 nurul efha October 18, 2012 03:26

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

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.
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.

 misagh October 21, 2012 17:59

Quote:
 Originally Posted by nurul efha (Post 387244) 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

 nurul efha October 21, 2012 20:47

Quote:
 Originally Posted by eng_s_sadeghi (Post 387678) 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...

 nurul efha October 21, 2012 20:49

Quote:
 Originally Posted by misagh (Post 387797) 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...

 Nickul October 27, 2012 14:03

Quote:
 Originally Posted by eng_s_sadeghi (Post 387678) 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:
 http://hpce.iitm.ac.in/website/Manua.../ug/img741.gif Note that for axisymmetric problems, this mass flow rate is the flow rate through the entire ( http://hpce.iitm.ac.in/website/Manua.../ug/img742.gif-radian) domain, not through a 1-radian slice.

 villager July 31, 2016 19:11

Quote:
 Originally Posted by Nickul (Post 388853) 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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