Question

How does the turbulent boundary layer vary with respect to the Reynolds number?

(a) Rex^–\(\frac {1}{5}\)

(b) Rex^–\(\frac {1}{4}\)

(c) Rex^–\(\frac {1}{2}\)

(d) Rex^-2

I have been asked this question in an interview for internship.

Question is from Turbulence Modelling topic in chapter Boundary Layers, Laminar & Turbulent Boundary Layers, Navier Stokes Solutions of Aerodynamics

Answer 1

The correct choice is (a) Rex^–\(\frac {1}{5}\)

The explanation is: The turbulent boundary layer thickness in an incompressible flow is given by:

δ = \(\frac {0.37x}{Re_x^{-1/5}}\)

Thus the turbulent boundary layer thickness varies as Rex^-1/5 whereas in case of laminar flow, it varies as Rex^-1/4.