Question

The efficiency of the vane is given by_________

(a) 1-V2^2/ V1^2

(b) 1-(V2^2/ V1^2)

(c) V2^2/ V1^2

(d) 1- V1^2

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

My question is taken from Force Exerted by a Jet on a Series of Vanes in portion Impact of Jets and Jet Propulsion of Fluid Mechanics

Answer 1

Right choice is (a) 1-V2^2/ V1^2

To explain: In a velocity triangle at the inlet and the outlet, the control volume is moving with a uniform velocity. Therefore, the momentum theorem of the control volume is at a steady flow. Thus, the efficiency of the vane is given by 1-(V2^2/ V1^2).