Question

The total skin-friction drag coefficient for laminar flow with Reynolds number at the trailing edge being Rec=40000 and chord length is 1m, is _____

(a) 0.01328

(b) 0.00664

(c) 0.02656

(d) 0.664

The question was asked during an interview for a job.

My question is based upon Laminar Flow topic in portion Incompressible Flow over Airfoils of Aerodynamics

Answer 1

The correct choice is (a) 0.01328

The explanation: The total skin-friction drag coefficient for laminar flow is twice the value of the skin-friction drag coefficient for laminar flow, Cf=\(\frac {1.328}{\sqrt{Re_c}}\). Putting the given values, we get the answer as 0.01328.