Question

Question #1 : a) Why liquids are usually transported in circular pipes? b) Which fluid at room temperature requires a larger pump to flow at a specified velocity in a given pipe; water or engine oil? Why? c) Consider the flow of air and water in pipes of the same diameter, at the same temperature, and at the same mean velocity. Which flow is more likely to be turbulent? Why? d) How is head loss or energy loss related to pressure loss? For a given fluid, explain how you would energy loss to pressure loss. e Explain why the friction factor is independent of the Reynolds number at very large Reynolds numbers.

Answer 1

(1) Answer:- Fluids are usually flow in circular pipe because pipes with a circular cross section can with stand large pressure differences between the inside and outside without undergoing any distortion.

(2) Answer:- Engine oil requires larger pump because oil has much larger density compare to water.

(3) Answer:- Reynolds number(Re) = V*D/(kinematic viscosity)

Kinematic viscosity(v) of water is less than kinematic viscosity of air. Water will be more turbulent than air.

(4) Answer:- Head loss (h_L) = (pressure loss P_L ) /(pg)

Head loss related to pressure loss(P_L)

We know that

h_L = (V₁ – V₂)²/(2g)

here we see this due to change in head loss energy loss is also changed. By help of above formula we can change energy loss to pressure loss.

(5) Answer:- At very large Reynolds numbers the friction factor is independent of the Reynolds number. Because the thickness of laminar sub layer decreases with increasing Reynolds number.