Question

Define circulation.

(a) Line integral around a closed loop enclosing the airfoil

(b) Line integral around an open loop enclosing the airfoil

(c) Line integral around an in loop enclosing the airfoil

(d) Line integral of airfoil

This question was addressed to me by my school principal while I was bunking the class.

My question comes from The Kutta-Joukowski Theorem topic in chapter Inviscid & Incompressible Flow of Aerodynamics

Answer 1

Correct choice is (a) Line integral around a closed loop enclosing the airfoil

Explanation: Circulation is defined as the line integral around a closed loop enclosing the airfoil of the component of the velocity of the fluid tangent to the loop. To calculate the force on an airfoil, outside the boundary layer the vorticity is zero, everywhere the circulation is the same around every circuit.