Hello,
I was taking a look
Hello,
I was taking a look at the calculation of yplus with the checkYPlus utility, but isn't this in fact a check for ystar? Ystar = rho*Cmu^0.25*sqrt(k)*y/mu yplus = rho*sqrt(tau_w/rho_w)*y/mu Thus Ystar is related to the turbulent kinetic energy and yplus to the wallshearstress, or am I now overlooking something? kind regards Guido 
Hey Guido
I'm running some calculations with RSTMs and while checking y+ for the first cell I recognized the same. Checking via the yPlusRAS command creates totally different values than the calculation with: y+ = Utau*y/nu with Utau = SQRT(Tau_wall/rho) Meanwhile did you figured out something to avoid this curio? Thanks and regards, Sven 
although its old.but I have found that yPlusRAS uses y* furmula in return of y+.could anyone guide me or give an explanation on why?:)

Quote:
Check out this post, Niklas has came up with a solution by modifying the file yPlusLES.C: http://www.cfdonline.com/Forums/ope...tml#post280296 best 
thanks Mojtaba.
but my case is compressible.do you know how to change the incompressible yPlus code? and also it doesn't compile in OF 2.2.0: Code:
ehsan@Ehsancom:~/Desktop/yPlus$ wmake 
Quote:
Which file did you use to compile? 
the second file he has put there.are they only for LES?

1 Attachment(s)
Quote:
the uploaded file is the utility I used for incompressible flows using RAS models. 
it gives this error.maybe it should modified for 2.2.0 version.
Code:
ehsan@Ehsancom:~/Desktop/yPlus$ wmake 
Quote:
There is no nutWallFunctionFvPatchScalarField.H inside yPlus.C that it can't find. instead nutkWallFunctionFvPatchScalarField.H is used. Are you sure you are using the file I uploaded? I don't know if it has changed in OF 2.2 or not. maybe its dependency issues. 
yes.I use that file.
can anyone help how change it to adapt to 2.2.0 version? 
in mutkWallFunctionFvPatchScalarField the equation uses for yplus is related to ystar not yplus
Code: Code:
ystar=pow(0.09,0.25)*sqr(k)*nearDist()/mu Code:
yplus=rho*u_star*y/mu which u*=aqrt(taw_w/rho) in the code of mut : Code: 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); } } 
could anyone have a look to resolve the error?
Code:
ehsan@Ehsancom:~/Desktop/yPlus$ wmake 
Hi Mojtaba,
I used your yPlus utility. I ran a case using KKLOmega turbulence model with simpleFoam solver. I ran your yPlus utility after the simulation was completed. For every time step I am getting values of yPlus as "min=0, max=0, average=0". How to fix this? Also, the yPlusRAS utility that comes with OF2.1.1 also has the problem of reporting y* instead of y+? Regards, Mayank 
Hi,
My understanding of this issue is that the quantities of yplus and ystar are approximately the same for equilibrium turbulent boundary layers. In equilibrium turbulent boundary layers, the friction velocity u_tau is approximately equal to Cmu^0.25*sqrt(k) in the loglaw region, which is exactly the definition of u_star. However, in local nonequilibrium conditions such as separation and reattachment, a deviation exists between u_tau and u_star, as u_tau is no longer approximately equal to Cmu^0.25*sqrt(k). I look forward to anyone correcting me if I am wrong here. 
As regards OpenFOAM , nutLowReWallFunctions/mutLowReWallFunctions calculates yplus according to the wall shear stress and the friction velocity. Other wall functions for nut/mut, such as mutkWallFunction, calculates yplus in the way of calculating ystar.
You can borrow the code for the calculation of yplus in nutLowReWallFunctionFvPatchScalarField.C/mutLowReWallFunctionFvPatchScalarField.C to write your own utility or function object to calculate yplus. 
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