Water flows through a pipe line of 12 cm diameter under a pressure of 20 N/cm² with average velocity of 4 m/s. Find the total energy in pressure head per unit weight of water at the cross-section which is 10 m above the datum line.
The total energy or pressure head of liquid in pipe line by Bernoulli’s equation is:
H=z+\frac{P}{w}+\frac{V^{2} }{2g} (i)
Substituting the given values of head, depth of flow and velocity head in Eq. (i), we get
H=10+\frac{20 \times (10)^{4} }{1000 \times 9.81}+\frac{4^{2} }{2 \times 9.81 }
Therefore, H= 31.2 m of water