[Other] Two different y+ values for same mesh, one with wall function and the other without

faiazk · October 16, 2019, 12:05

Hello Everyone,

Hope you all are doing good. I have been working with OpenFOAM for a year now. I am looking into use of wall functions and appropriate yplus range for my problem. I have one specific question. I am using K omega SST model for my case.

I created a mesh; used wall functions in one case and used no wall function in the other case. I was trying to see the impact of this on my results. With the same mesh, when I used yPlus utility to check yPlus values I found two different values. They are:

1. with wall function: yplus: 56
2. No wall function: yplus: 12

Is this meaningful? Based on the use of wall functions in Openfoam, should the yplus value vary for same mesh?

Please let me know.

Thanks

Regards,
Faiaz

Carlo_P · October 16, 2019, 17:37

The yplus value can be different for the same mesh if the speed next to the wall change.
The speed can change do if your simulation has different set up, such as using wall function and not using wall function.

You can avoid the use of wall function if y+ is less then 1, otherwise, you should use.

Check this post: Wall function usage

October 16, 2019, 12:05	Two different y+ values for same mesh, one with wall function and the other without	#1
faiazk New Member Faiaz Khaled Join Date: Oct 2017 Location: United States of America Posts: 17 Rep Power: 8	Hello Everyone, Hope you all are doing good. I have been working with OpenFOAM for a year now. I am looking into use of wall functions and appropriate yplus range for my problem. I have one specific question. I am using K omega SST model for my case. I created a mesh; used wall functions in one case and used no wall function in the other case. I was trying to see the impact of this on my results. With the same mesh, when I used yPlus utility to check yPlus values I found two different values. They are: 1. with wall function: yplus: 56 2. No wall function: yplus: 12 Is this meaningful? Based on the use of wall functions in Openfoam, should the yplus value vary for same mesh? Please let me know. Thanks Regards, Faiaz

October 16, 2019, 17:37		#2
Carlo_P Senior Member Carlo_P Join Date: May 2019 Location: Italy Posts: 176 Rep Power: 8	The yplus value can be different for the same mesh if the speed next to the wall change. The speed can change do if your simulation has different set up, such as using wall function and not using wall function. You can avoid the use of wall function if y+ is less then 1, otherwise, you should use. Check this post: Wall function usage