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#1 |
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Banned
ehsan
Join Date: Oct 2012
Location: Iran
Posts: 1,106
Rep Power: 0 ![]() |
where does this formula that is used for yPlus come from?!
I have not seen such expression so far but differently.where can I find an article or page about such expression? Code:
turbulence {
type executeIfObjectExists;
objectName k;
checkType true;
// checkType false;
objectType volScalarField;
objectShouldExist true;
// writeDebug true;
readDuringConstruction false;
functions {
yPlusField
{
type expressionField;
outputControl timeStep;
outputInterval 1;
fieldName yPlus;
expression "pow(0.09,0.25)*sqr(k)*nearDist()/mu";
autowrite true;
}
yPlusWall
{
type patchExpression;
expression "pow(0.09,0.25)*sqr(k)*dist()/mu";
accumulations (
min
max
average
);
patches (wall);
verbose true;
}
}
}
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#2 |
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Banned
ehsan
Join Date: Oct 2012
Location: Iran
Posts: 1,106
Rep Power: 0 ![]() |
i have found that this expression is y star not y plus.
How such an obvious mistake has been made here in a tutorial of OpenFOAM? |
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#3 |
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Banned
ehsan
Join Date: Oct 2012
Location: Iran
Posts: 1,106
Rep Power: 0 ![]() |
how can modify it to true expression?very important to me.
(my case is compressible,kOmegaSST turbulence model) |
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#4 |
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Banned
ehsan
Join Date: Oct 2012
Location: Iran
Posts: 1,106
Rep Power: 0 ![]() |
in mutkWallFunctionFvPatchScalarField the equation uses for y-plus is related to y-star not y-plus
Code:
y-star=pow(0.09,0.25)*sqr(k)*nearDist()/mu Code:
y-plus=rho*u_star*y/mu which u*=aqrt(taw_w/rho) in the code of mut : Code:
forAll(mutw, faceI)
{
label faceCellI = patch().faceCells()[faceI];
scalar yPlus =
Cmu25*y[faceI]*sqrt(k[faceCellI])/(muw[faceI]/rhow[faceI]);
if (yPlus > yPlusLam_)
{
mutw[faceI] = muw[faceI]*(yPlus*kappa_/log(E_*yPlus) - 1);
}
}
thanks.
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#5 |
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Banned
ehsan
Join Date: Oct 2012
Location: Iran
Posts: 1,106
Rep Power: 0 ![]() |
I reported this as a bug:
http://www.openfoam.org/mantisbt/view.php?id=835 could anyone help.the answer is not acceptable to me.I want to know the true yPlus in a turbulent kOmegaSST with yplus<=1 to be sure that separation regions and adverse pressure gradients are calculated and included truely not through some "wall-function rough estimations". maybe someone dosn't want to use wall functions. I want "y plus" exactly and only "y plus" not "y star" or any other thing instead of "y plus" ![]() could anyone help? please don't hesitate. (I have see some modified files for yPlusRAS but they don't work in 2.2.0 version) |
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