Question

The mixing length for a 2-D turbulent boundary layer depends on ____________

(a) the distance from the wall and the boundary layer thickness

(b) the distance from the wall and von Karman’s constant and dimensionless distance

(c) von Karman’s constant

(d) the boundary layer thickness

This question was addressed to me at a job interview.

This key question is from Mixing Length Turbulence Model topic in chapter Turbulence Modelling of Computational Fluid Dynamics

Answer 1

Correct option is (b) the distance from the wall and von Karman’s constant and dimensionless distance

Easiest explanation: The mixing length for a 2-D turbulent boundary layer is given by κy[1-exp⁡(y^+/26)]. Where, κ is the von Karman’s constant which is equal to 0.41. y is the distance from the wall. y^+ is the dimensionless distance.