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

Results in zero drag

Results in infinite drag

Results in body forces

Results in formation of vortices behind the body

Correct Answer : Results in zero drag

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.

Recently Updated in Aerodynamics Questions

If the Laplace equation is satisfied by the velocity potential, then the fluid flows.

True

False

Can Not Say

None of the above

Correct Answer : Option (A) : True

Explanation : For the fluid to flow, it is essential for the velocity potential ? to satisfy the Laplace equation. If the condition is not met, the fluid does not flow and has zero velocity.

Thus, the condition for the fluid to flow is :

What is the nature of the flow having a velocity potential?

Viscous

Inviscid

Rotational

Irrotational

Correct Answer : Option (D) : Irrotational

Explanation : For irrotational flow, curl of velocity vector yields zero. In case the curl of any vector is zero i.e.∇ × V = 0, where V is a vector, it is also expressed in the form of ∇ζ where ζ is a scalar function. In case of irrotational flow, velocity potential ? is the scalar function. Hence if the flow has a velocity potential, it automatically implies that it is irrotational.