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Porous Media Pressure Jump Coefficient

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Old   April 14, 2014, 03:01
Default Porous Media Pressure Jump Coefficient
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Hi Guys,

Can someone please help me on how to calculate the pressure jump coeff. (C2) in the equation
below. I have already calculated a value using Idelcik's book but I'm still not sure whether the value I calculated is correct or not.
By the ways I am simulating perforated plates ,for gas distribution, with circular holes which I intend to replace with a porous media to cut the simualtion time.



Any Help is Appreciated, Thank You Very Much.
-will
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Last edited by will321321; April 15, 2014 at 22:08.
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Old   April 14, 2014, 09:29
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Edmund Singer P.E.
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That is a function of your device. Is there data for it?

I have used this website for generic perforated plates before.

http://www.iperf.org/pressure.html

I have also built smaller cfd models of the device only and ran CFD to get those coefficients which I then use in larger models without the device.
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Old   April 14, 2014, 21:27
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Hi Singer1812,

Thank you very much for your help, unfortunately I dont have any Data on the perforated plate (experimental data) because I am trying to design the device (Perforated Plate) through CFD.

If you dont mind, can you please help me on how to get C2 by using a smaller scale model?. I mean I can get the Pressure drop of the plate but how about the C2.

Please bear with me, Thank you.

-will

Last edited by will321321; April 15, 2014 at 22:08.
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Old   April 15, 2014, 09:11
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Edmund Singer P.E.
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Perhaps I am not understanding.

If you have the pressure drop (I assume you have it for various flow rates), then getting C2 and mu/alpha for that equation is a simple curve fit. MS excel will do that for you, use 2nd order polynomial fit and force the fit to go through zero.
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Old   April 15, 2014, 20:52
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Hello Springer,

Now I Understand... its the method that is descrided in the fluet manual (Deriving the Porous Coefficients Based on Experimental Pressure and Velocity Data).

One more question Sir, I am calculating a Negative Value for permeability should I just use the value as it is or neglect the negative value.

Thank you so much.
-will

Last edited by will321321; April 15, 2014 at 23:49. Reason: Additional Question
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Old   April 24, 2014, 10:31
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Hi guys,

I have an update and another problem on my work.
With Singer's earlier help, I have now calculated the permeability and resistance coefficient (C2) of the more or less 50% plate porosity from a separate test simulation (DP = 1.9545 V^2 + 0.0216 V). But I again ran into a problem and was hoping that someone more knowlegable could help me.

PROBLEM BACKGROUND:
I have a negative system ductwork with perforated plate along the entire cross-section serving as screen (where an induced fan is located further down stream of the layout). My setup is to have the outlet as negative pressure and inlet boundary defined as massflow rate. when I used the calculated permeability and C2 into the simulation, the resulting pressure at the inlet becomes positive! Which should not be since the entire system is under suction from the ID-Fan.

Any help would be most welcome.:c onfused:

Thank you.

-will
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