Question

According to d’Alember’s paradox, what happens when the flow over a body is irrotational?

(a) Results in infinite drag

(b) Results in zero drag

(c) Results in formation of vortices behind the body

(d) Results in body forces

The question was posed to me by my college professor while I was bunking the class.

My enquiry is from Irrotational Flow in portion Velocity Potential Equation of Aerodynamics

Answer 1

Correct option is (b) Results in zero drag

The explanation: In real life scenario, it is impossible to have only irrotational region over the body. The flow comprises of both rotational and irrotational region. According to d’Alember’s paradox, having irrotational and inviscid flow throughout results in zero drag which is impossible in real life hence it’s a paradox.