Numerical Problems with Non-Linear RAS models

cfdmarkus · February 9, 2010, 05:15

Hi all,

I am trying to simulate the flow in a channel with periodic hills using a nonlinear RAS model and simpleFoam (incompressible).
The mesh is of good quality and I am using upwind schemes for all quantities apart from the non-linear stress term:
div(nonlinearStress) Gauss linear;

My problem is that I get massive oscillations in almost all flow quantities, see attached pictures!

I am quite sure that the oscillations are caused by using: div(nonlinearStress) Gauss linear;
Therefore, I have tried to use a limited version (e.g. div(nonlinearStress) Gauss limitedLinear 1; ) but this does not work.

Does anyone know how a bounded version of Gauss linear can be used on div(nonlinearStress)?

Many Thanks
Markus

ingcorra · August 18, 2015, 05:48

I have implemented several nonlinear models and I am facing exactly the same issue with all of them. Have you found a solution?

RicardoFE95 · November 12, 2018, 17:08

I am facing the same issue while running LienCubicKE model. Not only are oscillations ocurring but the normal Reynolds stress in the stream direction is showing negative values which is nonphysical. I'll attach pictures of the fields once I'm able to. While running the other NLEVM available ShihQuadraticKE I am not running into these issues.

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August 18, 2015, 05:48		#2
ingcorra New Member My Name Join Date: Jan 2013 Posts: 13 Rep Power: 13	I have implemented several nonlinear models and I am facing exactly the same issue with all of them. Have you found a solution?

November 12, 2018, 17:08		#3
RicardoFE95 New Member Join Date: Apr 2018 Posts: 4 Rep Power: 8	I am facing the same issue while running LienCubicKE model. Not only are oscillations ocurring but the normal Reynolds stress in the stream direction is showing negative values which is nonphysical. I'll attach pictures of the fields once I'm able to. While running the other NLEVM available ShihQuadraticKE I am not running into these issues.