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May 15, 2016, 15:46 |
how to report y+ in paper?
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#1 |
New Member
Join Date: Feb 2016
Posts: 20
Rep Power: 10 |
As the title says, when you write an paper, you will mention your turbulence model(k-w SST) and y+. But here y+ is area-weighted average of the whole wall region? or Maximum value? The reason why I ask it is that I will have a a higher y+(1~2) on the other side of the wall when I create a flow angle in transonic flow but the overall area-weighted average is still below 1(0.72)...Anyone has suggestions on how to report y+? or I just report the 'maximum area-weighted average y+ in all cases is 0.72'?
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May 16, 2016, 10:31 |
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#2 |
Senior Member
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,673
Rep Power: 65 |
This is also why it's sooooo important to plan your approach. I've always found that it was much better to report cell sizes for this exact reason. In other words, what were your meshing constraints that eventually gave rise to the mesh that would produce such a solution? Cell sizes are unambiguous and give you all the information that you need to repeat the problem, whereas y+ changes depending on the solver and settings used.
The maximum and average value of y+ gives some useful guidelines. The location where the maximum y+ occurs is also very useful, because it tells the next person where they want to focus their attention. Presenting y+ works really well in a presentation, but in a paper, just give me the damn grid spacing and I'll know what your resolution is. I only need to know y+ to understand what modelling regime you are in. e.g. if your mesh is globally y+>30 or globally y+<5. Or some hybrid. The rest of the information is just details. In general, nobody cares if your mesh has an average y+ of 0.1, 0.11, or 0.23. Although there is a "cool factor" to showing off that your y+ is smaller than the next person, do we really need a dick measuring contest in scientific publications? What matters is that y+ ~1. If you are just targeting y+ ~1 then simple state so. If y+ is very important to your particular scenario, a detailed 1D line plot of y+, 2D contour plot, or full 3D surface plot might be better suited than trying to report a simple number. For example, what information do you want to convey? Use the appropriate figure for doing so. The real question is: what actually matters? |
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