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

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.

How about your local pressures calculated in Fluent? Match with experimental?

[zhhjll]

I want to model a micro filter, This filter (membrane) is rectangular (10×5 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]

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]

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

[quantities]

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]

@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]

Originally Posted by quantities

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]

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

In quantities' post, corresponds to in (7-2) and corresponds to . I'm not sure about the in quantities's equation.