# viscous resistance coefficients in Porous media

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 May 12, 2004, 22:50 viscous resistance coefficients in Porous media #1 choyong Guest   Posts: n/a 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 Takue likes this.

 May 13, 2004, 11:44 Re: viscous resistance coefficients in Porous medi #2 co2 Guest   Posts: n/a 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.

 May 14, 2004, 10:50 Re: viscous resistance coefficients in Porous medi #3 Allan Walsh Guest   Posts: n/a How about your local pressures calculated in Fluent? Match with experimental?

 June 21, 2011, 18:08 #4 New Member   zohreh Join Date: Feb 2011 Location: Tehran Posts: 20 Rep Power: 14 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

 September 14, 2013, 06:18 hello guys, #5 New Member   Anonymous Join Date: Jun 2013 Posts: 9 Rep Power: 11 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 ?

 September 16, 2013, 02:34 #6 Senior Member     A-A Azarafza Join Date: Jan 2013 Posts: 226 Rep Power: 13 @dreamlifter747 I suppose that you should consider your own experimental set-up to extract the interest variables. Refer to Fluent theory guide. __________________ Regard yours

 September 16, 2013, 03:37 #7 New Member   Join Date: Sep 2013 Location: Shanghai China Posts: 6 Rep Power: 11 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. A CFD free user likes this.

 April 22, 2014, 01:46 #8 New Member   Join Date: Apr 2014 Posts: 29 Rep Power: 11 @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

December 15, 2014, 15:15
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isaac
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Quote:
 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
can u say to me what is your source?for this note?

 December 15, 2014, 20:01 #10 Senior Member   François Grégoire Join Date: Jan 2010 Location: Canada Posts: 392 Rep Power: 16 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.