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.

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'm using 2D planar...

I think so. Thanks...

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."

Mass flow rate and mass flux conversion from 3d to 2d axisymmetric.
 

Hello there,
I have a doubt of similar type
I have a 3d model which is now converted to 2d axisymmetric model.
In 3d I know the mass flux and mass flow rate, how do I convert both of these values to 2d.
Also I have to give supersonic pressure as input too. Now I know pressure condition in 3d. How do I find it in my 2d axisymmetric model?

Thank you!

If you have say a 3D pipe which you have turned into 2D axissymmetric then all the BCs are the same for 3D and 2D. The reason people struggle with 2D is when they two-dimensionalize a hummingbird.


Mass flow is the same in 2D axisymmetric and 3D (but not the same for 2D non-axisymmetric). Mass flux and pressure is the same always.