# yplus postProcessing formula

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 April 26, 2013, 08:16 yplus postProcessing formula #1 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,210 Rep Power: 19 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; } } }``` __________________ Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked.

 April 26, 2013, 22:18 #2 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,210 Rep Power: 19 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? __________________ Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked.

 May 2, 2013, 14:18 #3 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,210 Rep Power: 19 how can modify it to true expression?very important to me. (my case is compressible,kOmegaSST turbulence model) __________________ Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked.

 May 5, 2013, 08:34 #4 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,210 Rep Power: 19 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)` y-star is related to turbulent kinetic energy while y-plus relates to friction velocity(that relates to wall skin friction in its own) 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.``` __________________ Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked.

 May 5, 2013, 11:16 #5 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,210 Rep Power: 19 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) __________________ Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked.

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