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

I got this question by my school teacher while I was bunking the class.

My question is based upon Drag on a Sphere topic in division Boundary Layer Flow & Forces on Sub-merged Bodies of Fluid Mechanics

Answer 1

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

The explanation is: 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).