Question

If ∇*V is not equal to zero, then the flow is __________

(a) steady

(b) unsteady

(c) rotational

(d) irrotational

I have been asked this question by my college professor while I was bunking the class.

My doubt is from Angular Velocity, Vorticity, Strain topic in division Aerodynamics – Fundamental Principles and Equations of Aerodynamics

Answer 1

Correct answer is (c) rotational

For explanation I would say: In rotational flow, the fluid element has a finite angular velocity which means the element can undergo rotation and as well as distortion. The amount of distortion depends on the velocity field.