The difference in the water surface level of two reservoirs which are connected by a siphon is 8 m. The length of siphon is 600 m and its diameter 0.3 m. If the siphon is running full, then what is the discharge ? (Take f = 0.02)

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UPSC ESE (Prelims) Civil Engineering 19 Feb 2023 Official Paper
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  1. 3.242 m3/s
  2. 2.117 m3/s
  3. 1.842 m3/s
  4. 0.137 m3/s

Answer (Detailed Solution Below)

Option 4 : 0.137 m3/s
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ST 1: UPSC ESE (IES) Civil - Building Materials
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Detailed Solution

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Concept:

Discharge can be calculated by the expression for head loss for pipes:

\(h_f=\frac{8Q^2}{\pi^2g}\times\frac{fL}{D^5}\)

where, 

Q = discharge

f= friction factor

g = acceleration due to gravity

D = diameter of pipe

L = length of pipe

Calculation:Given

hf = 8 m

L = 600 m

D = 0.3 m

g = 9.81 m/s2 

Head loss for pipe is

\(8=\frac{8Q^2}{\pi^2\times9.81}\times\frac{0.02\times600}{0.3^5}\)

\(Q=0.14m^3/s\)

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