Honeycomb Porous medium

ahmed ibrahim · August 25, 2021, 14:36

Hello everyone
I'm working on a project to reduce the heat transfer in plate in a square pipe. i have to create a porous medium in this plate. my question is, how to define the honeycomb parameters in CFX ?

ahmed ibrahim · August 27, 2021, 05:21

can anyone help me please

ghorrocks · August 27, 2021, 05:44

Have you looked in the documentation and read what parameters CFX needs to define a porous region? I would have thought that was the obvious place to start.

If you have read the documentation - then what are you having troubles defining?

ahmed ibrahim · September 9, 2021, 21:01

Hello Ghorrocks,
thank you for your Answer. I have red the documentation and what parameters CFX needs to define a porous region. I understood that a Honeycomb or Perforated plat are Anistropic Porous medium and they could have Directional Loss Coefficient. Ialso have red some letrature about Honeycomb/ Perforated plate and i saw in some of them the Kperm was 5.73 mm/s ( which i couldnt implement in CFX ) and some of them was 1E-5,-6, -9 , -10 ,,,,,m^2 which i could implement in CFX.
I still dont understand how CFX understand that these numbers are for honeycomb or other thing.
one honeycomb can have many deffirent values.
how can i define it exactly to get the result i want.

siw · September 11, 2021, 06:40

Do you have the experimental data for the pressure drop ( $\Delta p$ ) across the plate as a function of volumetric flow rate (

) or superficial velocity ( $U_{s}$ )? This is the velocity associated with the volumetric flow rate and frontal area ( $Q=AU_{s}$ ), not the true velocity within the porous media and the area of the filter pathways.

For a subdomain you can input permeability in units of [m^2] and loss coefficient in units of [1/m], but the latter might not be significiant. Let us assume you have a plot of $\Delta p$ vs

and curve fitted to give $\Delta p=aQ+bQ^{2}$ which is also $\Delta p=aAU_{s}+b\left(AU_{s}\right)^{2}$ . CFX-Solver Theory Gude explains the Darcy-Forchheimer equation. You can then determine your $K_{perm}$ and $K_{loss}$ from the curve fit, fluid properites ( $\rho$ and $\mu$ ) and filter thickness ( $\Delta n$ ):

$aA=\frac{\mu \Delta n}{K_{perm}}$

$\rightarrow$

$K_{perm}=\frac{\mu \Delta n}{aA}$
$bA^{2}=K_{loss} \frac{\rho}{2} \Delta n$

$\rightarrow$

$K_{loss}=\frac{2bA^{2}}{\rho \Delta n}$

Use the directional streamwise multipler to ensure this is applied to the streamwise direction only.

August 25, 2021, 14:36	Honeycomb Porous medium	#1
ahmed ibrahim New Member Ahmed Ibrahim Abdalla Join Date: Aug 2021 Posts: 3 Rep Power: 4	Hello everyone I'm working on a project to reduce the heat transfer in plate in a square pipe. i have to create a porous medium in this plate. my question is, how to define the honeycomb parameters in CFX ?

August 27, 2021, 05:44		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Have you looked in the documentation and read what parameters CFX needs to define a porous region? I would have thought that was the obvious place to start. If you have read the documentation - then what are you having troubles defining? __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

September 11, 2021, 06:40		#5
siw Senior Member Stuart Join Date: Jul 2009 Location: Portsmouth, England Posts: 733 Rep Power: 25	Do you have the experimental data for the pressure drop ( $\Delta p$ ) across the plate as a function of volumetric flow rate () or superficial velocity ( $U_{s}$ )? This is the velocity associated with the volumetric flow rate and frontal area ( $Q=AU_{s}$ ), not the true velocity within the porous media and the area of the filter pathways. For a subdomain you can input permeability in units of [m^2] and loss coefficient in units of [1/m], but the latter might not be significiant. Let us assume you have a plot of $\Delta p$ vs and curve fitted to give $\Delta p=aQ+bQ^{2}$ which is also $\Delta p=aAU_{s}+b\left(AU_{s}\right)^{2}$ . CFX-Solver Theory Gude explains the Darcy-Forchheimer equation. You can then determine your $K_{perm}$ and $K_{loss}$ from the curve fit, fluid properites ( $\rho$ and $\mu$ ) and filter thickness ( $\Delta n$ ): $aA=\frac{\mu \Delta n}{K_{perm}}$ $\rightarrow$ $K_{perm}=\frac{\mu \Delta n}{aA}$ $bA^{2}=K_{loss} \frac{\rho}{2} \Delta n$ $\rightarrow$ $K_{loss}=\frac{2bA^{2}}{\rho \Delta n}$ Use the directional streamwise multipler to ensure this is applied to the streamwise direction only.

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August 27, 2021, 05:21		#2
ahmed ibrahim New Member Ahmed Ibrahim Abdalla Join Date: Aug 2021 Posts: 3 Rep Power: 4	can anyone help me please

September 9, 2021, 21:01		#4
ahmed ibrahim New Member Ahmed Ibrahim Abdalla Join Date: Aug 2021 Posts: 3 Rep Power: 4	Hello Ghorrocks, thank you for your Answer. I have red the documentation and what parameters CFX needs to define a porous region. I understood that a Honeycomb or Perforated plat are Anistropic Porous medium and they could have Directional Loss Coefficient. Ialso have red some letrature about Honeycomb/ Perforated plate and i saw in some of them the Kperm was 5.73 mm/s ( which i couldnt implement in CFX ) and some of them was 1E-5,-6, -9 , -10 ,,,,,m^2 which i could implement in CFX. I still dont understand how CFX understand that these numbers are for honeycomb or other thing. one honeycomb can have many deffirent values. how can i define it exactly to get the result i want.