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-   -   Simulating inlet consisting of many small holes (http://www.cfd-online.com/Forums/openfoam-solving/58467-simulating-inlet-consisting-many-small-holes.html)

christian October 14, 2008 10:53

I wonder if someone could help
 
I wonder if someone could help me with the following. Air is pumped into a room through a plate with a lot of small holes. If I don't account for this, the velocity will be wrong given a specific volume flow which I know.

On the other hand, accounting for these tiny holes through meshing is out of the question. So what can I do? The area of the inlet will be too big if I disregard the fact that the inlet really is a perforated plate.

But what if I increase the fluid density on the inlet. Then the momentum (rho*U) will be correct as well as the volume flow (U*A). I mean, inside the domain, density is evaluated from other properties (I'm using bouyantSimpleFoam and buoyantFoam), not solved as a transport equation. This should work, right or wrong? But there will be a momentum over the entire inlet, in reality this momentum only occurs through the holes of the perforated plate. Consequences?

Hope to hear your comments.

Best regards,
Christian Lindbäck

uwe October 15, 2008 01:35

Hi Christian, why don't you
 
Hi Christian,

why don't you model the perforated plate as a porous zone? If you have different volume flows the pressure drop over the plate will change automatically.

Uwe

christian October 15, 2008 02:11

Hi Uwe, What I want is to s
 
Hi Uwe,

What I want is to set a volume flow V on an inlet with area A. However, due to the fact that the inlet is a perforated plate, I would want the velocity not to be U = V/A but V/(f*A) where f is an area factor between 0 and 1. Another option would be to increase the density at the inlet boundary so that the momentum is correct.

How can I do this with a porous zone?

uwe October 15, 2008 02:56

Hi Christian, why don't you
 
Hi Christian,

why don't you extend the computational domain and set the inlet at a certain distance of the porous plate?

Uwe


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