[ANSYS Meshing] What is the criteria of Y plus

sakura006 · July 27, 2018, 12:07

I am performing a mesh independent study for a CFD model of a room (50ft x 18ft x 10ft). So the grid size is comparatively large, about 5in near the wall. I use the k-e standard turbulence model and standard wall function. Based on the simulation, I get a histogram of Y plus of the wall.

Y plus histogram of the wall
yplus.PNG
The average of y plus of the wall is 63

I read the fluent manual, I know that the y plus of the wall should be ranged from 30 to 300. My question is, should the average value of y+ be between 30 to 300, or the whole range of y+ be between 30 to 300? Is this mesh valid for k-e standard turbulence model with the standard wall function?

sakura006 · July 30, 2018, 10:09

Can anyone help me?

Gnak · July 30, 2018, 12:14

Far as I know when using a wall function, you should ensure that your prism layers are generated outside of the viscous sublayer & buffer layer.

That means that your y+ value should be greater than 30 and less 300 so that it remains within the log-law region.

Hope this helps, you should read up on the wall function that you are using for more info

Nam

Christophe · July 30, 2018, 22:14

Pretty sure FLUENT recommends Enhanced wall treatment for cases like this. That can handle a wide variety of y+ values much better.

July 27, 2018, 12:07	What is the criteria of Y plus	#1
sakura006 New Member Beichao Hu Join Date: Nov 2017 Posts: 9 Rep Power: 8	I am performing a mesh independent study for a CFD model of a room (50ft x 18ft x 10ft). So the grid size is comparatively large, about 5in near the wall. I use the k-e standard turbulence model and standard wall function. Based on the simulation, I get a histogram of Y plus of the wall. Y plus histogram of the wall yplus.PNG The average of y plus of the wall is 63 I read the fluent manual, I know that the y plus of the wall should be ranged from 30 to 300. My question is, should the average value of y+ be between 30 to 300, or the whole range of y+ be between 30 to 300? Is this mesh valid for k-e standard turbulence model with the standard wall function?

July 30, 2018, 12:14	Law of the wall	#3
Gnak New Member Nam Join Date: Jan 2018 Location: Canada Posts: 11 Rep Power: 8	Far as I know when using a wall function, you should ensure that your prism layers are generated outside of the viscous sublayer & buffer layer. That means that your y+ value should be greater than 30 and less 300 so that it remains within the log-law region. Hope this helps, you should read up on the wall function that you are using for more info Nam

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July 30, 2018, 10:09		#2
sakura006 New Member Beichao Hu Join Date: Nov 2017 Posts: 9 Rep Power: 8	Can anyone help me?

July 30, 2018, 22:14		#4
Christophe Member Join Date: Jan 2015 Posts: 62 Rep Power: 11	Pretty sure FLUENT recommends Enhanced wall treatment for cases like this. That can handle a wide variety of y+ values much better.