Question Bank • QB_EXP_SWCE_PIP_011 NAT • 2 Marks

Section 4: Soil and Water Conservation Engineering

Pipe Flow, Darcy-Weisbach & Minor Losses

Subtopic: Friction head loss and Darcy-Weisbach equation

Question Statement:

Water flows through a commercial pipe of length $450\text{ m}$ and internal diameter $15\text{ cm}$ at an average velocity of $1.8\text{ m/s}$. Taking the Darcy friction factor $f = 0.02$ and acceleration due to gravity $g = 9.81\text{ m/s}^2$, the head loss due to friction is ________ $\text{m}$ (round off to two decimal places).

Answer Key:

9.91

Step-by-Step Solution & Explanation

Using Darcy-Weisbach equation: $h_f = \frac{f L v^2}{2 g D}$ Given $f = 0.02$, $L = 450\text{ m}$, $v = 1.8\text{ m/s}$, $D = 0.15\text{ m}$: $h_f = \frac{0.02 \times 450 \times (1.8)^2}{2 \times 9.81 \times 0.15} = \frac{29.1600}{2.9430} = 9.91\text{ m}$
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