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|ID||Project||Category||View Status||Date Submitted||Last Update|
|0000835||OpenFOAM||[All Projects] Bug||public||2013-05-05 12:44||2014-02-10 13:18|
|Status||closed||Resolution||no change required|
|Target Version||Fixed in Version|
|Summary||0000835: mistake equation in yPlusRAS command|
|Description||in the code of yPlusRAS command the equation that is used is for y-star not y-plus and this causes some troubles.|
proposed to make another command for y-star and modify yPlusRAS command(I haven't tested for yPlusLES but probably it has the issue too)
|Tags||No tags attached.|
|The yPlusRAS command does not evaluate y+ directly but calls the yPlus function from the nut or mut BC.|
edited on: 2013-05-05 13:39
in mutkWallFunctionFvPatchScalarField the equation uses for y-plus is related to y-star not y-plus
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
label faceCellI = patch().faceCells()[faceI];
scalar yPlus =
if (yPlus > yPlusLam_)
mutw[faceI] = muw[faceI]*(yPlus*kappa_/log(E_*yPlus) - 1);
|Each nut/mut BC provides a consistent y+ function which takes into account the potentially extreme non-linear distribution of the near-wall velocity particularly for wall-functions. The simple nieve funcion for y+ using a simple estimate for the near-wall velocity gradient is appropriate for the laminar BC and for low-Re models in which the near-wall distributions are resolved.|
that you tell is true.but when having separation regions or high adverse pressure gradients in wall its more accurate that we use finer mesh near wall so that y-plus be around 1 to resolve viscous sub layer.this way we can include wall phenomenas exactly in return of have a coarser mesh and use wall-functions instead.
so,its good to have a real yPlus postProcessing tool as well as yStar for those that want to use coarser mesh and wall-functions and need it with true name.
Each nut/mut BC provides a consistent y+ function, for example compare the y+ functions in
Each provides a y+ function consistent with the wall-function formulation and hence the post-processing utility returns the y+ distribution used by and consistent with the wall-function.
the view is understandable in genaral.but 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 dosen't want to use wall functions at all when he has a low-Re grid mesh.
I want "y plus" exactly and only "y plus" not "y star" or any other thing instead of "y plus".
> kOmegaSST with yplus<=1
You need a low-Re form of kOmegaSST which does not use wall-functions and the nut/mut BC of which will provide the consistent y+.
so is there such version of kOmegaSST in OpenFOAM?
if i understand correctly then you say if anyone use yPlusRAS(or yPlusLES) he/she get an appropriate and correct value of y-plus regardless of using wall-functions or not(even if wall functions are not implemented it works well).is it so?
are you intending y-star values are a good estimate for y-plus values in all situations,or i'm wrong?
|We have not yet been sponsored to implement a low-Re version of kOmegaSST but we have implemented kkLOmega which is a low-Re k-omega model with support for transision. If you would like us to implement a low-Re version of kOmegaSST for you contact us via enquiries and we can discuss a contract to cover it. We would also implement appropriate BCs and the correspending y+ function for post-processing.|
is kkLOmega suitable for internal flow with a finer mesh near the wall and regions far the wall?
I did an enquiry.
Low Reynolds-number k-kl-omega turbulence model for
Turbulence model described in:
D. Keith Walters, Davor Cokljat
"A Three-Equation Eddy-Viscosity Model for Reynold-Averaged
Navier-Stokes Simulations of Transitional Flow"
J. Fluids Eng. 130(12), 121401 (Oct 24, 2008)
|2013-05-05 12:44||immortality||New Issue|
|2013-05-05 12:54||henry||Note Added: 0002159|
|2013-05-05 12:54||henry||Status||new => closed|
|2013-05-05 12:54||henry||Assigned To||=> henry|
|2013-05-05 12:54||henry||Resolution||open => no change required|
|2013-05-05 13:34||immortality||Note Added: 0002160|
|2013-05-05 13:34||immortality||Status||closed => feedback|
|2013-05-05 13:34||immortality||Resolution||no change required => reopened|
|2013-05-05 13:39||immortality||Note Edited: 0002160||View Revisions|
|2013-05-05 14:23||henry||Note Added: 0002161|
|2013-05-05 14:23||henry||Status||feedback => closed|
|2013-05-05 14:23||henry||Resolution||reopened => no change required|
|2013-05-05 14:47||immortality||Note Added: 0002162|
|2013-05-05 14:47||immortality||Status||closed => feedback|
|2013-05-05 14:47||immortality||Resolution||no change required => reopened|
|2013-05-05 15:00||henry||Note Added: 0002163|
|2013-05-05 15:00||henry||Status||feedback => closed|
|2013-05-05 15:00||henry||Resolution||reopened => fixed|
|2013-05-05 16:19||immortality||Note Added: 0002164|
|2013-05-05 16:19||immortality||Status||closed => feedback|
|2013-05-05 16:19||immortality||Resolution||fixed => reopened|
|2013-05-05 16:24||henry||Note Added: 0002165|
|2013-05-05 16:24||henry||Status||feedback => closed|
|2013-05-05 16:24||henry||Resolution||reopened => no change required|
|2013-05-05 18:01||immortality||Note Added: 0002166|
|2013-05-05 18:01||immortality||Status||closed => feedback|
|2013-05-05 18:01||immortality||Resolution||no change required => reopened|
|2013-05-05 18:37||henry||Note Added: 0002167|
|2013-05-05 18:37||henry||Status||feedback => closed|
|2013-05-05 18:37||henry||Resolution||reopened => no change required|
|2013-05-05 19:33||immortality||Note Added: 0002168|
|2013-05-05 19:33||immortality||Status||closed => feedback|
|2013-05-05 19:33||immortality||Resolution||no change required => reopened|
|2013-05-05 19:37||henry||Note Added: 0002169|
|2013-05-05 19:37||henry||Status||feedback => closed|
|2013-05-05 19:37||henry||Resolution||reopened => no change required|