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-   -   porous media: Fluent or Star-CD? (http://www.cfd-online.com/Forums/main/5509-porous-media-fluent-star-cd.html)

 Igor December 5, 2002 16:16

porous media: Fluent or Star-CD?

I need to model flow of incompres. viscous Newtonian fluid through porous media.

Problem: Rigid porous media is located between two cylinder surfaces and may rotate as a solid body. Fluid flows through sidewalls from inside to outside the media and goes out into a pipe on sidewall of other fixed cylinder with the same axis as porous one. There is another rotating cylinder with perforated sidewalls may be included inside inner (empty?) space of porous cylinder. Inlet flow occurs from orifice in center of topside of the system. FLow of fluid in pure fluid region suppose to be turbulent with Re about 10,000 Gaps between cylinders are not so big. About 1/20 of radii.

Questions are that:

1.In General: which code Fluent or Star-CD is best choice?

I read just on-line documentations about FLuent and my understanding (may be I am wrong) is

FLuent allows model porous media using two sinks (located in space occupied by porous media) in momentum equation of pure fluid. Linear term is associated with Darcy's law, and quadr. term is associated with Forchcheimer.

2.Does the equation contain Brinkman-like term similar to standard viscousity dissipation term? May be I missed this and it does. So, is this possible to use tensor form of effective Brinkman viscousity?

3.Darcy's coeff can be established in tensorian form but Forchheimer cannot. Is this so?

4.If I set Forchheimer coeff in zero, is that possible to specify slip velocity on the boundary between porous media and pure fluid flow ( I'm assumening there is not Brinkman viscosity as well in this case)? If it's not then which boundary conditions (actually- slip velocity value)are applied there by default?

5.Could I specify Coriolis forces inside porous media as a user's subroutine if I use moving bodyfitted reference frame or Fluent does this automaticaly?

6.Could I specify different dissipative terms (representing porous media) instead of standard terms?

7.Does velocity in momentum equation contain an adjustment of its value in accordance with porosity (somthing like v_porous=v_pure/porosity)?

8.Could I set simultaneously turbulent regime of flow in region of pure fluid flow and laminar regime inside porous media?

I read a little about Star-CD and it looks like it has some advantage because it allow establish different models in different regions simultaniously. I mean that Star-CD for instance is able to solve full Navier-Stoks system in pure fluid flow area and say Darcy's equation in form "vector of velocity= coefficient*gradient of pressure" in area of porous media and then it somehow makes these two solution coupled. Is my understanding right? Of course, all questions from above are still interestng for me in this case too.