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viscous resistance coefficients in Porous media

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Old   May 12, 2004, 22:50
Default viscous resistance coefficients in Porous media
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choyong
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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
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Old   May 13, 2004, 11:44
Default Re: viscous resistance coefficients in Porous medi
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co2
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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.

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Old   May 14, 2004, 10:50
Default Re: viscous resistance coefficients in Porous medi
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Allan Walsh
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How about your local pressures calculated in Fluent? Match with experimental?
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Old   June 21, 2011, 18:08
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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
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Old   September 14, 2013, 06:18
Default hello guys,
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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 ?
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Old   September 16, 2013, 02:34
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I suppose that you should consider your own experimental set-up to extract the interest variables. Refer to Fluent theory guide.
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Old   September 16, 2013, 03:37
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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.
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Old   April 22, 2014, 01:46
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@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
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Old   December 15, 2014, 16:15
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Quote:
Originally Posted by quantities View Post
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?
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Old   December 15, 2014, 21:01
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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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