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Old   October 14, 2010, 02:59
Default Concept behind Y+
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siddharth jain
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hello all,

can anybody explain me the concept behind Y+...........how do we set the value of Y+.....and how we calculate ?

what if the value of Y+ is very large or very less........?

thanx...........
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Old   October 15, 2010, 05:36
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dst
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Hi sidspark12,

all depends on your turbulence model. Wrong y+ parameters can(!) lead to wrong functioning of turbulence model (but, not so easy, as usual - everything depends on everything).

Let's say that one general approach (but not the rule) for y+ for two-equation models is
y+ ~ 1 for k-w
y+ ~ 30 for k-e

Of course, it is quite difficult to have constant y+ in all the surfaces, but usually you can try to be near to that values.

For y+ information you can check in solver's manuals - like in CFX manual or Fluent manual.

Regards,
DST
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Old   October 15, 2010, 07:03
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Hello DST

thanx...a ....lot...

Right now i am solving the case of FRANCIS TURBINE. for that i am using k-e model......and the value of y+ is around 12........now in my case the value of y+ is not same for every element because of the bldae design. .........now as u said in k-e model the value of y+ is near 30..........so how should i improve the value of y+.......?

after this i will also solve the same case with k-w model........

thanx......
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