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-   -   Help: Porous media inputs (http://www.cfd-online.com/Forums/fluent/47675-help-porous-media-inputs.html)

William March 20, 2008 11:01

Help: Porous media inputs
 
Hi, I a 4th year mechanical engineering student.

As part of my 4th year investigation, I am modelling an axi-symmetric simulation of a thin perforated disc in a water flow of 0.5m/s.

The disc has about 19% porosity (total hole area). What boundary conditions (in the porous zone BC tool) would best simulate the disc and how can I equate this value of porosity directly to the user inputs in Fluent 6.3?

Help would be very much appreciated.

Thanks in advance!

Isaac March 20, 2008 14:47

Re: Help: Porous media inputs
 
If you just have this thin disc inside a pipe for example and you're trying to simulate the restriction provided by this flow, I think it is better to use a porous jump condition for the disc instead of modeling it as a porous medium. The solution tends to be numeically more stable using the jump BC. Look at Fluent's user guide to specify parameters for a PJ boundary. It should be fairly straight forward.

William March 20, 2008 15:34

Re: Help: Porous media inputs
 
Cheers for the response,

The disc is modelled in a huge domain to simulate open flow.

So far my simulations using porous media with arbitrary input BC values have failed to create any velocity normal to the flow or recirculation. Which seems odd.

I'm quite interested in investigating the edge effects and wake formation around the disc. Will a PJ give an accurate representation of the flow dynamics around the disc?

Raj March 24, 2008 00:50

Re: Help: Porous media inputs
 
William, porous media or porous jump cannot predict the local effects i.e. effects close to the object in consideration. These options mainly meant to capture the effects of porous plate in the whole domain not to see the local effects as one expects. If local effects are very important for ur simulation then think of modeling and meshing the plate (if u dont have any constraint in doing so!), this is sometimes called as detailed way of modeling the porous plates.

Regards Raj


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