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Computing and printing y+

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Old   February 17, 2013, 18:04
Default Computing and printing y+
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Greg Power
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Has anyone generated code within SU^2 (or as a post-processing tool) to compute and print the y+ values at the first point adjacent to a viscous wall for turbulent flow?
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Old   February 21, 2013, 05:08
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Thomas D. Economon
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Hi Greg,

I don't personally have a snippet of code that can compute y+ within SU2, but just in case you are unfamiliar with it, the Pointwise website has a y+ calculator to give a quick estimate (http://www.pointwise.com/yplus/) based on flat plate theory.

Perhaps other folks have written a utility for this in SU2?

T
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Old   February 22, 2013, 09:38
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This kind of utility would be a good addition to SU2! It would make creating plots like figure 4 of this tutorial pretty easy:

http://adl.stanford.edu/docs/display...ent+Flat+Plate

As far as I know, the only way to reproduce this figure is by manually post-processing a TECPLOT output file. Being able to directly output local y+ would be pretty helpful in assessing the suitability of a grid for a particular problem!
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Old   February 27, 2013, 15:44
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Kevin Holst
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+1

I'd also like to see an easy y+ calculator added to SU2.
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Old   March 6, 2013, 12:25
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Francisco Palacios
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Quote:
Originally Posted by grjmpower View Post
Has anyone generated code within SU^2 (or as a post-processing tool) to compute and print the y+ values at the first point adjacent to a viscous wall for turbulent flow?
Hi Greg,
Thanks for you feedback,

We have added that capability in the current version of the code
http://su2.stanford.edu/download/svn/SU2_Rev1206.zip

Best,
Francisco
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Old   March 13, 2013, 14:57
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Greg Power
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Francisco,

Thanks! However, I downloaded the link above and did not see the y+ calculation output. Do I need an input parameter to turn this on?

I also downloaded 2.0.1 and did not see any y+ calculation method.


Greg
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Old   March 21, 2013, 19:43
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I haven't tried it out yet, but a look at the v.2.0.2 code seems to indicate that the Y+ output is now present (SU2_CFD->src->output_structure.cpp):

Code:
   
 
  if ((solver == NAVIER_STOKES) || (solver == RANS)) {
   for(iPoint = 0; iPoint < geometry->GetnPoint(); iPoint++) {
    aux_friction[iPoint] = 0.0;
    aux_heat_transfer[iPoint] = 0.0;
    aux_y_plus[iPoint] = 0.0;
   }
   for (iMarker = 0; iMarker < config->GetnMarker_All(); iMarker++)
    if (config->GetMarker_All_Plotting(iMarker) == YES) {
     for(iVertex = 0; iVertex < geometry->nVertex[iMarker]; iVertex++) {
      iPoint = geometry->vertex[iMarker][iVertex]->GetNode();
      aux_friction[iPoint] = FlowSolution->GetCSkinFriction(iMarker,iVertex);
      aux_heat_transfer[iPoint] = FlowSolution->GetHeatTransferCoeff(iMarker,iVertex);
      aux_y_plus[iPoint] = FlowSolution->GetYPlus(iMarker,iVertex);
     }
    }
  }
 
....
 
 
/*--- Write the skin friction coefficient variables ---*/
   if ((solver == NAVIER_STOKES) || (solver == RANS) || (solver == FREE_SURFACE_NAVIER_STOKES) || (solver == FREE_SURFACE_RANS)) {
    if (geometry->node[iPoint]->GetBoundary()) {
                    if (incompressible) SurfFlow_file << " " << aux_friction[iPoint] << " " << aux_y_plus[iPoint];
                    else SurfFlow_file << " " << aux_friction[iPoint] << " " << aux_heat_transfer[iPoint] << " " << aux_y_plus[iPoint];
                }
Implemented here (SU2_CFD->src->solution_direct_mean.cpp):

Code:
                /*--- Compute y+ and non-dimensional velocity ---*/
                FrictionVel = sqrt(fabs(WallShearStress)/Density);
                YPlus[iMarker][iVertex] = WallDistMod*FrictionVel/(Viscosity/Density);
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Old   March 22, 2013, 01:35
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I tried it and its even available in this version:
http://su2.stanford.edu/download/svn/SU2_Rev1206.zip

You need to open the surface file and you will see the variable called y-plus together with cp, cf and heat transfer coefficient.
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