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-   -   [GAMBIT] Asking Y plus (http://www.cfd-online.com/Forums/ansys-meshing/70095-asking-y-plus.html)

teguhtf November 14, 2009 07:10

Asking Y plus
 
Dear All,
In simulating airfoil, i use y+ = 1 for thin layer. However, I don't know the correct value of grow ratio b/a and number of row in GAMBIT??
Help me out this problem!!!:)
Thanks
teguhtf

PSYMN November 15, 2009 17:16

Problem Dependent.
 
These are up to the user and are highly problem dependent. If you don't already have a preference, then you should start with a ratio of 1.2 (most common).

As for number of layers, this should be enough to capture the thickness of your boundary layer velocity profile, but not so thick that it causes you too much meshing trouble.

Try 5, or try 21, solve, and look at the boundary layer velocity profiles... Which works best for your type of model? You want to see a smoothly transitioning boundary layer profile that goes from 0 at the wall up to the free-stream velocity (should approach asymptoticly )before the top of the prism stack.

Was 21 layers overkill or does it look like you need more?

teguhtf November 21, 2009 21:11

Thank you for your reply,
Well, My problem is How to get Right value of Cd & Cl between experiment and
simulation. Can you explain the Y+ value of other boundary condition?? Do you have reference?? Btw, I've try
5 to 10 layers. But it doesn't work!!:( My simulation is just 2D so i can use prism.
Thanks for helping
Teguh


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