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-   -   How to define the porous inertial resistance and viscous resistance of porous media? (http://www.cfd-online.com/Forums/star-ccm/103787-how-define-porous-inertial-resistance-viscous-resistance-porous-media.html)

pinfan143 June 27, 2012 00:54

How to define the porous inertial resistance and viscous resistance of porous media?
 
hello everyone


I have two questions about porous media. can you help me? thanks a lot.
1. How to define the porous inertial resistance and viscous resistance of porous media? what value can I use to input in ccm+?



for example. I know air flux ,pressure drop and the shape of the porous media.


(1). A cuboid, the thickness is c, and the Flow direction is thickness direction ,then i can use excel to analog polynomial curve: y=aX˛+bX.(y=static pressure drop,X= flow velocity)


(2). A cylinder, the thickness is c, and the flow direction is along radial direction form out to the inner. Of course i can use excel to analog polynomial curve: y=aX˛+bX.


but what can i do the next?


2. You know when I calculate the flow velocity, I need to use the air flux to divide by section area. It is very easy to gain the section area in cuboid model, but what about the cylinder??

siara817 June 28, 2012 03:33

Usually the resistances are in the order of thousands, except for the direction that the fluid can move easier ( for example in the case of filter, the resistance will be in the order of 10). good luck

abdul099 July 6, 2012 18:24

For the cylinder, I would use the average velocity as long as there is no huge difference between min and max velocity. So when you divide the volume flow rate by some cross sectional area, use the mantle area of a cylinder with the mean radius.
Calculate a and b and put it in the region values. For the radial direction of a cylinder, you might create a cylindrical coordinate system first.
When you don't want to allow a flow in axial or tangential direction, put a maximum of 1000 times the resistance in radial direction. Otherwise it might get unstable.

pinfan143 July 10, 2012 00:15

Quote:

Originally Posted by abdul099 (Post 370161)
For the cylinder, I would use the average velocity as long as there is no huge difference between min and max velocity. So when you divide the volume flow rate by some cross sectional area, use the mantle area of a cylinder with the mean radius.
Calculate a and b and put it in the region values. For the radial direction of a cylinder, you might create a cylindrical coordinate system first.
When you don't want to allow a flow in axial or tangential direction, put a maximum of 1000 times the resistance in radial direction. Otherwise it might get unstable.

Thank you very much. your reply is so important and precious to me.

sahra July 19, 2015 16:06

Hi
I'm trying to model vegetation as 3D porous media. As I am an architecture, have some queries, hope someone can help me out.


Is there any relationship between pressure drop and pressure loss coefficient?
I do not know how to set these two parameters in fluent: Viscous resistance coefficients and Inertial resistance. How can I get these?


Thanks.

MBdonCFD July 21, 2015 11:52

sahra, I have a spreadsheet I can share. send me a private message with your email address.


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