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-   -   viscous resistance coefficients in Porous media (http://www.cfd-online.com/Forums/fluent/33717-viscous-resistance-coefficients-porous-media.html)

choyong May 12, 2004 22:50

viscous resistance coefficients in Porous media
 
I have a question about setting resistance coefficients in a porous media problem.

Based on my experiment, I knew some info on pressure drop, so I calculated permeability(alpha called in Fluent 6.1). In Fluent 6.1 pannel, is it correct that i put 1/alpha as a resistance coefficients? The value is 8682372. (alpha=0.000000115). I got a converged solution, but I am not sure whether I did it right.

Last question is about what the physical/superficial velocity is in perous media. I read a old manual(6.0), which did not explain well about physical velocity. Which is recommeded to set a porous media problem?

Million thanks in advance.

cho

co2 May 13, 2004 11:44

Re: viscous resistance coefficients in Porous medi
 
cho:

settting up of coeff is explained very well in the fluent manual. please read 6.19.6 User Inputs for Porous Media carefully -- you dont need anyones advice on that -- if you have specific question about the content of this page, let know.

now about physical vel -- the way i understand it is as follows : please some one correct me if i am wrong.

porous media is basically just a momentum sink and generally in all the porous media related equations, we need superficial vel. that is not the actual vel with which you fluid is moving in the pores -- but physical velocity kind of gives you a measure of that actual fluid velocity.


Allan Walsh May 14, 2004 10:50

Re: viscous resistance coefficients in Porous medi
 
How about your local pressures calculated in Fluent? Match with experimental?

zhhjll June 21, 2011 18:08

I want to model a micro filter, This filter (membrane) is rectangular (105 cm) with the thickness 12e-5. so,I calculate this parameters from Ergun equation which D=1e-6, because of the Micro filter type. is this assumption true??
i think this is very thin filter so there in not flow through in the membrane, in this situation is inertial coefficieant higher in Y direction? or not?when i set y-direction inertial coefficient higher than x-direction got better answer! is this resonable?

I am looking forward to hearing from you.
Sincerely yours

dreamlifter747 September 14, 2013 06:18

hello guys,
 
I have trouble finding the alpha and beta values for modelling plasma (blood ) flow through a porous media which acts as the filter. All i have is the porosoity report and material properties.
Is it possible to calculate the inertial and viscous co-efficients ?

A CFD free user September 16, 2013 02:34

@dreamlifter747
I suppose that you should consider your own experimental set-up to extract the interest variables. Refer to Fluent theory guide.

quantities September 16, 2013 03:37

The superfical velocity = volume flow rate / flow area of porous media.
physical velocity = superfical velocity / porosity.
If you have some experiment data of pressure drop, you can fit them by a quadratic function: dP = a*v^2 + b*v + c. (v is superfical velocity)
The inertial coeff. = 2*a/density;
viscous coeff. = b/dynamic viscosity.

will321321 April 22, 2014 01:46

@quantities

I am getting a negative value for permeability since my graph has a negative linear coeff. and I cannot input a negative value for permeability in the porous media should I just neglect it being negative?

Thank you in advance.

-will

isaac2014 December 15, 2014 16:15

Quote:

Originally Posted by quantities (Post 451933)
The superfical velocity = volume flow rate / flow area of porous media.
physical velocity = superfical velocity / porosity.
If you have some experiment data of pressure drop, you can fit them by a quadratic function: dP = a*v^2 + b*v + c. (v is superfical velocity)
The inertial coeff. = 2*a/density;
viscous coeff. = b/dynamic viscosity.

hi
tnx about your this comment
can u say to me what is your source?for this note?

macfly December 15, 2014 21:01

Look at equation (7-2) here: https://www.sharcnet.ca/Software/Flu...sect_porous_mv

In quantities' post, a corresponds to \frac{C_2\rho}{2} in (7-2) and b corresponds to \frac{\mu}{\alpha}. I'm not sure about the c in quantities's equation.


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