y+ value for k-epsilon Model

yoser · July 26, 2018, 02:40

Hi all
I am working on 3D simulation for my model and used k-ε TM with standard wall function. So,the values of y+ <30. Is it true y+ value that for models mentioned k-epsilon? If not, what is the certain range of y+ value for this TM.

Thanks,

LuckyTran · July 26, 2018, 02:43

There are blending functions to make the wall functions play nice so that you don't strictly need to make any y+ criteria except small. But it's nicer to have a globally y+<10 or so such that everything is in the linear regime or avoid the buffer region between 10-30 and make all your y+>30. The y+ criteria isn't actually for the turbulence model but for the wall function being used.

yoser · July 26, 2018, 03:05

Thank you to fast reply LuckyTran. You mean my result value for y+ is not true and shoud be in range less than 10.

LuckyTran · July 26, 2018, 11:52

Sorry I don't understand your question. y+ is y+, you get what you get. If you want a desired y+ then you need to go back and remesh. My point is that you can have just about any value of y+ and still have quite a reasonable result.

July 26, 2018, 02:40	y+ value for k-epsilon Model	#1
yoser New Member Yoser Join Date: Jul 2018 Posts: 5 Rep Power: 9	Hi all I am working on 3D simulation for my model and used k-ε TM with standard wall function. So,the values of y+ <30. Is it true y+ value that for models mentioned k-epsilon? If not, what is the certain range of y+ value for this TM. Thanks,

July 26, 2018, 02:43		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,836 Rep Power: 68	There are blending functions to make the wall functions play nice so that you don't strictly need to make any y+ criteria except small. But it's nicer to have a globally y+<10 or so such that everything is in the linear regime or avoid the buffer region between 10-30 and make all your y+>30. The y+ criteria isn't actually for the turbulence model but for the wall function being used. yoser likes this.

July 26, 2018, 11:52		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,836 Rep Power: 68	Sorry I don't understand your question. y+ is y+, you get what you get. If you want a desired y+ then you need to go back and remesh. My point is that you can have just about any value of y+ and still have quite a reasonable result. yoser likes this.

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July 26, 2018, 03:05		#3
yoser New Member Yoser Join Date: Jul 2018 Posts: 5 Rep Power: 9	Thank you to fast reply LuckyTran. You mean my result value for y+ is not true and shoud be in range less than 10.