# yplus for film cooling in gas turbine blades

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 April 19, 2013, 18:44 yplus for film cooling in gas turbine blades #1 New Member   omar Join Date: Apr 2010 Posts: 23 Rep Power: 9 Hi everybody i`m modelling film cooling in a gas turbine blade with cooling holes in leading edge, i dont know wich one must be the y plus value for heat transfer in the blade surface. Iwas reading in numeca manuals that a value of y plus .1 is suitable, b my mesh is structured but isnt so fine, and i was reading that with values of y+> 30 i can reach good results in heat transfer, i'm simulating in fluent 14, using k-e, can anybody suggest me a y plus value to work in my simulation. thanks in adavance

 April 20, 2013, 04:17 #2 New Member   Esteban Join Date: Jul 2012 Posts: 13 Rep Power: 7 Hi, I alsol don't really know but once your computation is launched, you can adapt the mesh thanks to your results. Tab : Adapt -> y+/y*->choose to refine or coarsen -> mark to show you if your values seem modify something and adapt to change your mesh only in FLUENT itself. Valio

 April 20, 2013, 09:38 #3 New Member   omar Join Date: Apr 2010 Posts: 23 Rep Power: 9 thanks a lot Valio, i'm goint to refine the mesh in Fluent, can i refine the mesh before to start a new simulation or i need to reach the convergence first? and now that the mesh is refined is my y+ (.1) correct or i need to try with a new y plus value?. thanks again friend

 April 20, 2013, 10:40 #4 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,358 Blog Entries: 6 Rep Power: 45 Or you can use Yplus calculator to find the first layer distance and over all boundary layer thickness from flat plate boundary layer thickness formula. Length may be chord length of blade or any local length of film cooling holes. For heat transfer calculation I heard Y+ should be less than 1, even of order 0.1. Check literature.

April 20, 2013, 11:57
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Esteban
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Quote:
 Originally Posted by galapago thanks a lot Valio, i'm goint to refine the mesh in Fluent, can i refine the mesh before to start a new simulation or i need to reach the convergence first? and now that the mesh is refined is my y+ (.1) correct or i need to try with a new y plus value?. thanks again friend
Before to refine with Fluent, you need to get the first result.
Your mesh is not enough good, so it will not really converge (residual oscillation)

Once your mesh refined, launch again the computation and you can do again, computation/result/refine/computation etc until the "perfect" convergence
Your y+ depend of what you want, if you want a good resolution in the boundary layer, you need a really small y+ but I can't tell you the best choice

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