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-   -   Help with y+ (http://www.cfd-online.com/Forums/ansys/100227-help-y.html)

xdonu April 21, 2012 22:33

Help with y+
 
Hi,
I have an aircraft mesh in ICEM with prism i need to know how can i set ICEM to create a mesh with an specific y+, this is because i need to create 3 different mesh with y+=1, y+=2, y+=30.

Thanks

Far April 22, 2012 09:48

Here are the some hints :


1. Initial height = Y+ of the first cell

2. Total height = Total thickness of the boundary layer.

tanglei April 23, 2012 00:00

hi
I thinck you can only check the exactly value of Y+ until the simulation is done. before your simulation, you can only compute a Y+, but thia value may far from the real value.
and there is a website may be help
http://geolab.larc.nasa.gov/APPS/YPlus/

xdonu April 23, 2012 02:02

thank you both for your replies, i tried the way that far said by giving the initial height as if were the y+ it did not work sometimes with too low y+ like 4/9 or 2/3 it create a surface orientations issue which i couldn't fix, i agree with tanglei that there is no a method to specified a y+ directly from icem but i found a tool to get close if anyone has the same issue you could tell icem to create the initial height automatically by giving it a valuo of 0, when the mesh is computed go to edit mesh-split mesh and select split prism set the option of "fix initial height(this would be de ds that many calculator's give you when you choose the y+)" then apply, after this i always check the mesh for possible errors. Run your simulation in fluent and you should be close enough to change this value as you see fit if necessary.

xdonu April 23, 2012 12:58

I would like to add something that a ansys representative told me so if anyone else have this issue could work it out


In ICEM, you can create inflation layers (prism) and control the height of the first layer of prism, growth rates and number of layers of prism if you are creating a tetra -prism mesh. You can enter the height based on your Y+ requirements.

If you doing hexa, you can run a n o-grid through the model to capture inflation layers and controls the spacing under premesh parameters. You can set the spacing based on your Y+ requirements

There is no tool to specify your Y+ values in ICEM. You control it by specifying the element heights

I hope this would help to anyone with this issue

Far April 23, 2012 13:01

Quote:

Here are the some hints :


1. Initial height = Y+ of the first cell

2. Total height = Total thickness of the boundary layer.

Isn't already mentioned above :rolleyes:


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