[sanjiiv]

Hi scholars,
please tell me whats the need and purpose of refining the mesh and changing the values of y+ in turbulence flow model.
what is the limits of y+ for general and different problems,and how to calculate the value of y+ for different problems based on flow models.
finally, what is the purpose of Y*

thank you ,

[LuckyTran]

y* and y+ are both inner variables but use slightly different velocity scales for the inner velocity.

Depending on the model, the near-wall turbulence models used need a certain y+ or y*. Hence, your mesh should be fine or coarse enough to meet that criteria. These criteria depend entirely on your models you select (whether explicitly or implicitly).

[rdajohansson]

Y+ is calculated from the shear stress at the wall and can therefor be zero in some cases like stagnation and separation point. That's why there are a y* which is calculated from kinetic energy instead.