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-   -   Regarding Y+ (https://www.cfd-online.com/Forums/star-ccm/70235-regarding-y.html)

muthuvelcfd November 18, 2009 04:16
Regarding Y+
 
hi friend i have one doubt where i have to give the value of y + in starccm during simulation

aerospaceman November 18, 2009 19:28
Hey there,

As I understand it, you control your Y+ by the prism layer meshing settings.

There you can specify 1st wall thickness, total boundary layer thickness, number of cells etc.

These, as you know from your aerodynamics theory,then control your Y+.

If you want a more detailed explanation, let me know and I can supply you with the equations or links to them.

Hope this helps.

madcfd December 9, 2009 08:04
hi aerospaceman,

I am wondering how to figure out the boundary layer thickness for a nozzle flow.
Could you give me a detailed explanations, if possible with equations.

nvtrieu January 3, 2010 00:36
How to control the y+ value in Star-CCM+ ?
 
Quote:
Originally Posted by aerospaceman (Post 236813)
Hey there,

As I understand it, you control your Y+ by the prism layer meshing settings.

There you can specify 1st wall thickness, total boundary layer thickness, number of cells etc.

These, as you know from your aerodynamics theory,then control your Y+.

If you want a more detailed explanation, let me know and I can supply you with the equations or links to them.

Hope this helps.
Hello Aerospaceman,

I've been working with Star-CCM+ V3.06. I would like to know how to estimate the y+, as you said by using "prism layer mesher" right? so could you tell me more clearly?
thanks in advance!

email: trieuckgt@gmail.com
MSN: trieu.dut@livemail.com
YM: trieu_tme@yahoo.com

abdul099 January 7, 2010 08:24
Hi

i'm not sure, if i've understood your problem the right way.
A good estimation for the near wall prism layer of a flat plate could be found by using the tool on http://geolab.larc.nasa.gov/APPS/YPlus/ .
I'm doing simulation on an airfoil, so i specify the near wall prism layer thickness, using the value calculated by this tool, and it works very well.

After the simulation, you should do a scalar plot of the y+ value and adjust the near wall prism layer thickness if the y+ does not meet the requirements.

greetings

asherah February 21, 2010 14:41
Quote:
Originally Posted by abdul099 (Post 241778)
Hi

i'm not sure, if i've understood your problem the right way.
A good estimation for the near wall prism layer of a flat plate could be found by using the tool on http://geolab.larc.nasa.gov/APPS/YPlus/ .
I'm doing simulation on an airfoil, so i specify the near wall prism layer thickness, using the value calculated by this tool, and it works very well.

After the simulation, you should do a scalar plot of the y+ value and adjust the near wall prism layer thickness if the y+ does not meet the requirements.

greetings
Hiya thank you for sharing that calculator, in that calculator, there is a refrence length, and output, what are they?

Many thanks

Asherah

Maddin February 22, 2010 02:02
The output is the thickness of the first layer. For CCM you must calc it with the stretching factor and the numbers of layer.

Knigge46 February 13, 2015 04:53
Y+ Calculator
 
Hi Folks,
I don't know if you noticed, but CFD-Online has it's own Y+-Calculator!
It's very handy and gives you the near wall thickness as an ouput for your desired Y+-value.
It also gives a link to the wiki, where the formulas are explained in detail.


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