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-   -   Laminar Model (http://www.cfd-online.com/Forums/cfx/79112-laminar-model.html)

danillocafaldo August 12, 2010 20:54

Laminar Model
 
Hi,

I want to know if when I set the turbulence model to laminar CFX will solve exactly the Navier Stokes Equations.
CFX user guide says:

"Laminar flow is governed by the unsteady Navier-Stokes equation. The laminar option does not apply a turbulence model to the simulation and is only appropriate if the flow is laminar"

So, the fact thar it doesn't apply a turbulence model means that the equation that is solved is the NSE?
It seems true, but could be false I think.

What I want to simulate is a Mixing Layer. I will start with a tangent hyperbolic profile and analyse its development until it gets turbulent, so I have a laminar flow.

I want to know what CFX does solve for this case.

Thanks

ghorrocks August 13, 2010 06:13

Sounds like you need to read a basic CFD textbook. The laminar model is the Navier Stokes Equations, when you apply a turbulence model you then are talking about the Reynolds (or Fauve) averaged Navier Stokes equations. I recommend you read a CFD textbook to understand what the previous sentence is saying.

If your flow is laminar or just getting transitional a laminar model is probably OK. Sometimes you need the turbulence transition model, depends on the case. CFX supports both approaches.

danillocafaldo August 13, 2010 08:24

Thank you ghorrocks.

I'm starting my CFD study now I have a lot to learn.

I asked this because one told me that in CFX solver the laminar model was not implemented with the NSE but also with a RANS with such parameters that approximate the NSE.
Theoretically I know that laminar means NSE, without turbulence, but me question was how do the solver see this.

Regards

Josh August 13, 2010 15:28

Off-topic, but I thought I'd let you know you have a very cool name, Mr. dos Reis.

ghorrocks August 14, 2010 07:36

Quote:

I asked this because one told me that in CFX solver the laminar model was not implemented with the NSE but also with a RANS with such parameters that approximate the NSE.
I don't understand what you are saying here but when the laminar flow model is selected CFX does a numerical simulation of the Navier Stokes equations. When you select a Reynolds or Fauve averaged model it fires up the RANS. I have no idea what your friend is talking about.

danillocafaldo August 16, 2010 10:43

Ok Ghorrocks.
Thank you very much for your answer.

Thanks Josh.


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