Unable to get Yplus less than 1

zohaibaltaf.6 · December 23, 2019, 01:06

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

Joao Bomfim · December 25, 2019, 07:25

Hi. How you obtained y+ value?

zohaibaltaf.6 · January 1, 2020, 02:44

Using area weighted average over the wall

Roh · January 2, 2020, 06:03

Quote:

Originally Posted by zohaibaltaf.6

Using area weighted average over the wall

Why "area weighted average"?

Fluent has plot tools to plot the Y+ over a wall.

zohaibaltaf.6 · January 16, 2020, 12:59

thank you, i have also used plot tool and it shows different values at different patches

zohaibaltaf.6 · January 16, 2020, 13:01

Quote:

Originally Posted by zohaibaltaf.6

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

LuckyTran · January 17, 2020, 01:40

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.

December 23, 2019, 01:06	Unable to get Yplus less than 1	#1
zohaibaltaf.6 New Member Zohaib Altaf Join Date: Aug 2019 Location: Pakistan Posts: 9 Rep Power: 6	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

January 17, 2020, 01:40		#7
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,704 Rep Power: 66	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. zohaibaltaf.6 likes this.

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December 25, 2019, 07:25		#2
Joao Bomfim New Member João de Sousa Bomfim Neto Join Date: Oct 2017 Location: Maranguape, Ceará, Brasil Posts: 27 Rep Power: 8	Hi. How you obtained y+ value?

January 1, 2020, 02:44		#3
zohaibaltaf.6 New Member Zohaib Altaf Join Date: Aug 2019 Location: Pakistan Posts: 9 Rep Power: 6	Using area weighted average over the wall

January 16, 2020, 12:59		#5
zohaibaltaf.6 New Member Zohaib Altaf Join Date: Aug 2019 Location: Pakistan Posts: 9 Rep Power: 6	thank you, i have also used plot tool and it shows different values at different patches