Yplus Range

sasanghomi · July 3, 2018, 01:50

Dear friends,

Is there any reference in which I can find the instructions for Y+ in CFX software program? I know that in Fluent User Guide everything is clarified but in CFX software program I cannot find a comprehensive reference for acceptable rage of Y+ in different turbulent models.

Any help is appreciated deeply.

Best Regards

ghorrocks · July 3, 2018, 19:57

y+ is a universal definition so guidelines for Fluent will apply to CFX as well, assuming you are using them on equivalent turbulence models and wall functions.

But in short: If you are using wall functions then you must get y+>11. The exact y+ you need will be problem dependent so you need to do a sensitivity analysis to find that.

If you are integrating to the wall you need y+<1, but not too much smaller than 1.

Gert-Jan · July 4, 2018, 03:53

And if you use SST, you can live with a Yplus ranging from 0.1 up to 300.

siw · July 5, 2018, 03:29

Everyone who has questions about modelling boundary layers and y+ requirements should read these posts at LEAP Australia:

Tips & Tricks: Turbulence Part 1 - Introduction to Turbulence Modelling
https://www.computationalfluiddynami...nce-modelling/

Tips & Tricks: Turbulence Part 2 - Wall Functions and Y+ requirements
https://www.computationalfluiddynami...-requirements/

Turbulence Part 3 - Selection of wall functions and Y+ to best capture the Turbulent Boundary Layer
https://www.computationalfluiddynami...oundary-layer/

Turbulence Part 4 - Reviewing how well you have resolved the Boundary Layer
https://www.computationalfluiddynami...oundary-layer/

Tips & Tricks: Estimating the First Cell Height for correct Y+
https://www.computationalfluiddynami...t-cell-height/

sasanghomi · July 6, 2018, 06:18

Thank you so much for your comprehensive response.

July 3, 2018, 01:50	Yplus Range	#1
sasanghomi Senior Member Sasan Ghomi Join Date: Sep 2012 Location: Denmark Posts: 292 Rep Power: 16	Dear friends, Is there any reference in which I can find the instructions for Y+ in CFX software program? I know that in Fluent User Guide everything is clarified but in CFX software program I cannot find a comprehensive reference for acceptable rage of Y+ in different turbulent models. Any help is appreciated deeply. Best Regards

July 3, 2018, 19:57		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 18,017 Rep Power: 146	y+ is a universal definition so guidelines for Fluent will apply to CFX as well, assuming you are using them on equivalent turbulence models and wall functions. But in short: If you are using wall functions then you must get y+>11. The exact y+ you need will be problem dependent so you need to do a sensitivity analysis to find that. If you are integrating to the wall you need y+<1, but not too much smaller than 1. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

July 5, 2018, 03:29		#4
siw Senior Member Stuart Join Date: Jul 2009 Location: Portsmouth, England Posts: 746 Rep Power: 27	Everyone who has questions about modelling boundary layers and y+ requirements should read these posts at LEAP Australia: Tips & Tricks: Turbulence Part 1 - Introduction to Turbulence Modelling https://www.computationalfluiddynami...nce-modelling/ Tips & Tricks: Turbulence Part 2 - Wall Functions and Y+ requirements https://www.computationalfluiddynami...-requirements/ Turbulence Part 3 - Selection of wall functions and Y+ to best capture the Turbulent Boundary Layer https://www.computationalfluiddynami...oundary-layer/ Turbulence Part 4 - Reviewing how well you have resolved the Boundary Layer https://www.computationalfluiddynami...oundary-layer/ Tips & Tricks: Estimating the First Cell Height for correct Y+ https://www.computationalfluiddynami...t-cell-height/ AtoHM likes this.

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July 4, 2018, 03:53		#3
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,996 Rep Power: 29	And if you use SST, you can live with a Yplus ranging from 0.1 up to 300.

July 6, 2018, 06:18		#5
sasanghomi Senior Member Sasan Ghomi Join Date: Sep 2012 Location: Denmark Posts: 292 Rep Power: 16	Thank you so much for your comprehensive response.