Question

The boundary layer thickness for turbulent flow at a distance x with Reynolds number Rex is δ. Which is____

(a) Directly proportional to \(\sqrt[5]{x}\)

(b) Inversely proportional to \(\sqrt[5]{Re_x}\)

(c) Directly proportional to Rex

(d) Inversely proportional to x

This question was addressed to me in my homework.

My query is from Turbulent Flow in division Incompressible Flow over Airfoils of Aerodynamics

Answer 1

Right choice is (b) Inversely proportional to \(\sqrt[5]{Re_x}\)

Easy explanation: The boundary layer thickness for an incompressible, turbulent flow over a flat plate, at a distance x where Reynolds number is Rex is given by δ=\(\frac {0.37x}{\sqrt[5]{Re_c}}\). Thus, the thickness is indirectly proportional to \(\sqrt[5]{Re_x}\).