# Computing and printing y+

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 February 17, 2013, 18:04 Computing and printing y+ #1 New Member   Greg Power Join Date: Jan 2013 Posts: 9 Rep Power: 5 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?

 February 21, 2013, 05:08 #2 Super Moderator   Thomas D. Economon Join Date: Jan 2013 Location: Stanford, CA Posts: 270 Rep Power: 6 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

 February 22, 2013, 09:38 #3 New Member   Join Date: Jan 2013 Posts: 12 Rep Power: 5 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!

 February 27, 2013, 15:44 #4 New Member   Kevin Holst Join Date: Nov 2012 Posts: 4 Rep Power: 5 +1 I'd also like to see an easy y+ calculator added to SU2.

March 6, 2013, 12:25
#5
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Francisco Palacios
Join Date: Jan 2013
Location: Long Beach, CA
Posts: 342
Rep Power: 6
Quote:
 Originally Posted by grjmpower 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

Best,
Francisco

 March 13, 2013, 14:57 #6 New Member   Greg Power Join Date: Jan 2013 Posts: 9 Rep Power: 5 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

 March 21, 2013, 19:43 #7 New Member   Join Date: Jan 2013 Posts: 12 Rep Power: 5 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);```

 March 22, 2013, 01:35 #8 Senior Member   Join Date: Nov 2010 Posts: 133 Rep Power: 7 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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