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Momentum source / porous loss

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Old   May 14, 2011, 06:53
Default Momentum source / porous loss
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ijk
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Hi all,

I am modelling a radiator and want to account for the pressure loss across it.

I have data of pressure loss vs velocity.

From that data and the depth of the radiator, I worked out my linear and quadratic resistance coefficients.

I then set up a test case to see if the CFX model gave me sensible results.
I set up a tunnel with the radiator in the middle and a velocity inlet of 10m/s. I used free slip walls.

The pressure drop from CFX was 266 Pa and it should be 230. Can anyone please suggest why the two are different?

Thanks,

ijk
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Old   May 14, 2011, 08:54
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siw
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Have you tried the CFX Catalytic Converter tutorial? That deals with flow through a porous medium and could assist in setting up your model.
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Old   May 15, 2011, 18:51
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http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F
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Old   May 16, 2011, 08:15
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Got it solved.

It was a bug in Excel - I plotted a polynomial trendline in excel and the coefficients it gave me were wrong.
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Old   May 20, 2011, 08:38
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Greg
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I'm trying to do the same thing - I have pressure drop vs. flow rate across a filter, and I need to include this loss in my CFX model. Can you share the spreadsheet or at least point me to the equations?

Thanks!
Greg
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Old   May 20, 2011, 10:30
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ijk
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I modelled the flow through a radiator so in my case the flow can only go in one direction. Therefore I used the directional loss model.

I simply plotted (pressure drop/depth of radiator) vs. velocity and fitted a second order polynomial to the data points. (this was the problem in excel)

The coefficients are the linear and quadratic resistance coefficients.
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