Question

Let y be the distance from the wall, ut be the shear velocity and ν be the kinematic viscosity. Which of these equations define y^+?

(a) y^+=y/utν

(b) y^+=utν/y

(c) y^+=(y ut)/ν

(d) y^+=ut/yν

I have been asked this question during an internship interview.

This intriguing question comes from Turbulence Modelling topic in division Turbulence Modelling of Computational Fluid Dynamics

Answer 1

Correct answer is (c) y^+=(y ut)/ν

The explanation: y^+ is the ratio of the product of the distance from the wall boundary and the shear velocity to the kinematic viscosity. This is given by the equation y^+=y ut/ν. This is why the value of y^+ increases with the distance from the wall.