GATE 2019 ME (ME2) – Question 53

Fluid Mechanics · Flow through pipes, head losses, bends and fittings · 2 marks · Numerical answer

Water flows through equal-circular-section pipes A and B of lengths 1.0 and 2.0 m respectively. Both flows are laminar and fully developed. Their frictional head losses are equal. Find volume-flow ratio QB/QA, to two decimal places.

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: .48 to .52

Explanation

Hagen–Poiseuille gives $\Delta p=128\mu LQ/(\pi D^4)$. Equal pressure drop, diameter and fluid imply constant LQ. Therefore $Q_B/Q_A=L_A/L_B=\mathbf{0.50}$.