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Unable to get Yplus less than 1

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Old   December 23, 2019, 01:06
Default Unable to get Yplus less than 1
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Zohaib Altaf
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Hello!

I am working on a developing flow through diffusing duct of aircraft.
Boundary conditions: pressure inlet & mass flow outlet
Model: k-omega SST
I am stuck in the results of yplus i.e.
Area weighted average of yplus at wall = ~70
As, model demands y+<1. I have checked different mesh sizes (b/w 1-20 million cells) but unable to get y+<1.
1st cell height = ~ 1x10^-6
Layers=~ 42
Height ratio = 1.2

Please help me in this. Thanks
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Old   December 25, 2019, 07:25
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Jo„o de Sousa Bomfim Neto
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Hi. How you obtained y+ value?
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Old   January 1, 2020, 02:44
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Using area weighted average over the wall
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Old   January 2, 2020, 06:03
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Quote:
Originally Posted by zohaibaltaf.6 View Post
Using area weighted average over the wall

Why "area weighted average"?


Fluent has plot tools to plot the Y+ over a wall.
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Old   January 16, 2020, 12:59
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thank you, i have also used plot tool and it shows different values at different patches
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Old   January 16, 2020, 13:01
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Quote:
Originally Posted by zohaibaltaf.6 View Post
thank you, i have also used plot tool and it shows different values at different patches
And somwhere it is close to 1 but other locations have higher y+ around 70
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Old   January 17, 2020, 01:40
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It's clear what you have to do to get a smaller wall y+. Make smaller cells there.


You probably will never get the wall y+ <1 globally. You can tinker with it for a month and you might end up with one location where it is 2.
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developing flow, diffusers, duct flow, k-w sst, yplus

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