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Boundary conditions for LaunderGibsonRSTM discussion

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Old   April 26, 2012, 06:43
Default Boundary conditions for LaunderGibsonRSTM discussion
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ms
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Hi everyone,

I've set up an incompressible, steady-state simulation of a static body in a freestream using the LaunderGibsonRSTM model for turbulence solving with simpleFoam and would like some discussion regarding appropriate boundary conditions. I am not using wall functions and have what I think is a good mesh of hexas in the boundary layer and tets outside. It is a half mesh,
with symmetry on all walls except the input and output. At the moment I'm using the following boundaryField entries:

0/R: noslipwall{type fixedValue; value uniform (0 0 0 0 0 0);}
inlet{type freestream; freestreamValue uniform (0 0 0 0 0 0};}
symmetry{type symmetryPlane;}
outlet{type freestream; freestreamValue uniform (0 0 0 0 0 0};}

0/U: noslipwall{type fixedValue; value uniform (0 0 0);}
inlet{type freestream; freestreamValue uniform (10 0 0);}
symmetry{type symmetryPlane;}
outlet{type freestream; freestreamValue uniform (10 0 0);}

0/p: noslipwall{type zeroGradient;}
inlet{type freestreamPressure;}
symmetry{type symmetryPlane;}
outlet{type freestreamPressure;}

0/epsilon: noslipwall{type fixedValue; value uniform 1E-10;}
inlet{type freestream; freestreamValue uniform 0.13;}
symmetry{type symmetryPlane;}
outlet{type freestream; freestreamValue uniform 0.13;}

0/k: noslipwall{type fixedValue; value uniform 1E-10;}
inlet{type freestream; freestreamValue uniform 0.1;}
symmetry{type symmetryPlane;}
outlet{type freestream; freestreamValue uniform 0.1;}

0/nut: noslipwall{type fixedValue; value uniform 1E-10;}
inlet{type calculated; value uniform 0.22;}
symmetry{type symmetryPlane;}
outlet{type calculated; value uniform 0.22;}

Do these boundary conditions seem reasonable? I'm using low relaxation values and the solution ticks for some time and then blows up with epsilon being bounded: this makes me doubt the boundary conditions; hence the request for discussion! Please,
any comments about past working cases using this turbulence model would be greatly appreciated!

As a footnote, I'm using the following solvers:

U: smoothSolver. p: GAMG. epsilon: PBiCG. R: PBiCG.
Best regards,

Mark.

Last edited by anothr_acc; April 26, 2012 at 09:27.
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Old   April 27, 2012, 10:17
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Equally, if somebody could give me a source of examples (other than $FOAM_TUTORIALS) I'd be happy to look further myself.
Best regards,
Mark.
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Old   April 30, 2012, 06:08
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Also, I've refined my mesh through the boundary layer and I'd like to turn off the wall functions used with this turbulence model. I've changed my constant/polyMesh/boundary file from using `wall' at the walls of my body, to `patch' in an attempt to do this and set U, R,
epsilon, k, nut to zero; and p to zeroGradient.

Is this the approach other people use to turn off the wall functions?

Best regards,

Mark.
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Old   May 14, 2014, 17:54
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Mark, did you ever figure this out? I'm having the same problem!
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