# Porous medium Settings(porosity settings) in CFX

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 November 12, 2017, 23:40 Porous medium Settings(porosity settings) in CFX #1 New Member   Ali Join Date: Apr 2016 Posts: 24 Rep Power: 8 Hi all, I want to simulate a porous material which is "anisotropic". For that I have to input meaningful porosity settings. Since it is an anistropic case, I have to choose the "Directional Loss". In this way I have to input : 1- Directional Loss : X-component , Y-component, Z-component 2- Permeability and Resistance Loss coeff. both in streamwise and transverse. I have two questions regarding these mentioned points : 1- What are exactly these X, Y, and Z components in the Directional Loss part and how are they calculated? (I could not find it in CFX Help) 2- I have an anistropic porous domain. So I have to have three different Permeability and Resistance Loss coefficients in each axis-->(x,y,z), but in the settings we can only specify Streamwise and Transverse Loss. So why is it like that ? I am looking forward to your help please

 November 14, 2017, 15:30 #2 Member   Join Date: Oct 2017 Posts: 89 Rep Power: 7

 November 14, 2017, 16:05 #3 New Member   Ali Join Date: Apr 2016 Posts: 24 Rep Power: 8 thank you for your comment, but I already went through the help and it does not answer my question.

February 18, 2018, 02:03
#4
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Bruno Raviolo
Join Date: Sep 2015
Posts: 6
Rep Power: 9
Quote:
 Originally Posted by vortex69 1- What are exactly these X, Y, and Z components in the Directional Loss part and how are they calculated? (I could not find it in CFX Help) 2- I have an anistropic porous domain. So I have to have three different Permeability and Resistance Loss coefficients in each axis-->(x,y,z), but in the settings we can only specify Streamwise and Transverse Loss. So why is it like that ?
I'm not sure if an answer at this time might actually still help, but here we go. I've already questioned myself about these parameters when I was modelling a curved wall made entirely of perforated bricks to allow unchecked windflow across a room.

1 - As of a directional loss model, you must inform the fluid's correct direction (streamwise) in the porous medium. In order to do this, CFX asks about this direction's vectorial components, which are based on the coordinate system from your model.

At least in my own workflow, I've faceted the single-curvature wall's geometry reasonably and then extracted the normal from each face, which thus gave me X, Y and Z components. I did this completely outside ANSYS, and only after that I informed CFX.

2 - Should my memory still be accurate, the directional loss model in CFX gives you three methods to calculate resistance loss. Once you realize that all inputs depends on the streamwise direction, things get easier.

Just be advised that the Resistance Loss coefficient is particulary nasty, as in real life it isn't a fixed calculated value, but rather heavily influenced by the angle of attack.

September 7, 2019, 01:51
#5
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Jerry
Join Date: Sep 2019
Location: Queensland, Australia
Posts: 17
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Quote:
 Originally Posted by ZeroState I'm not sure if an answer at this time might actually still help, but here we go. I've already questioned myself about these parameters when I was modelling a curved wall made entirely of perforated bricks to allow unchecked windflow across a room. 1 - As of a directional loss model, you must inform the fluid's correct direction (streamwise) in the porous medium. In order to do this, CFX asks about this direction's vectorial components, which are based on the coordinate system from your model. At least in my own workflow, I've faceted the single-curvature wall's geometry reasonably and then extracted the normal from each face, which thus gave me X, Y and Z components. I did this completely outside ANSYS, and only after that I informed CFX. 2 - Should my memory still be accurate, the directional loss model in CFX gives you three methods to calculate resistance loss. Once you realize that all inputs depends on the streamwise direction, things get easier. Just be advised that the Resistance Loss coefficient is particulary nasty, as in real life it isn't a fixed calculated value, but rather heavily influenced by the angle of attack.
Hi Bruno,

Thank you for your answer. I have the same questions as Ali did. After reading your reply, I am still confused about directional loss. Can you explain how to set the value of directional loss for X, Y and Z component? Actually, I know the permeability for X, Y and Z direction of my porous medium.

Your detailed explanation will be highly appreciated.

 Tags anisotropic material, ansys cfx, cfx, porous domain, porous medium