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Old   August 17, 2005, 08:21
Default Pressure Loss Definition.
  #1
Chirag
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My problem domain has a sub domain (a perforated grid plate) in flow stream. For this, I know %age open area. How can I define it in CFX so that I can get exact flow behavior?
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Old   August 17, 2005, 08:37
Default Re: Pressure Loss Definition.
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Indrajit
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U can create the same geomety using thin surface, that will be ideal one
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Old   August 17, 2005, 09:02
Default Re: Pressure Loss Definition.
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Chirag
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Thanks Indrajit.

But, how will I define pressure drop or %age opening for a thin surface? Also I can't model thousands of holes on that surface (perforated grid plate), as that will increase mesh size tremendously.

Is there any other way out?

Thanks again.
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Old   August 17, 2005, 18:31
Default Re: Pressure Loss Definition.
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Glenn Horrocks
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Hi,

Use a momentum source, or possibly a porous material. This will give you a number of pressure loss models to choose from so you can select the most appropriate one.

Glenn Horrocks
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Old   August 17, 2005, 23:51
Default Re: Pressure Loss Definition.
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Chirag
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I am trying to do it with "Momentum Source/Porous Loss Model" only. But I do not understand how to define X, Y & Z Cartesian Components under "Directional Loss Model" (when only available data to you is %age opening in grid plate)? Also, what else shall be defined in "Linear Resistance Coefficient" / "Quadratic Resistance Coefficient"?
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Old   August 18, 2005, 07:12
Default Re: Pressure Loss Definition.
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Michael Bo Hansen
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I tend to use the Handbook of Hydraulic Resistance by Idelchik when I have to determine the pressure drop coefficient of grids and other flow restrictions.
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Old   August 19, 2005, 13:50
Default Re: Pressure Loss Definition.
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Robin
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With CFX 10.0 there is a new "Pourous" Domain object. This allows you to specify both the volume fraction and the pressure drop characteristics.

Regards, Robin
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