Question

The skin-friction coefficient for turbulent flow Cf is proportional to Rec. The proportionality constant is_____

(a) 0.074

(b) 0.64

(c) 0.33

(d) 1.328

I had been asked this question in an international level competition.

The question is from Turbulent Flow topic in division Incompressible Flow over Airfoils of Aerodynamics

Answer 1

Correct choice is (a) 0.074

The best explanation: The coefficient of skin-friction drag for turbulent flow is given as Cf=\(\frac {0.074}{\sqrt[5]{Re_c}}\) where Rec is the Reynolds number at the trailing edge. The required constant is 0.074. For laminar flows, the constant of proportionality is different.