Question

A rectangular channel is 6m wide and discharges $30m^3{s}^{-1}$. The upstream depth is 2.0m, acceleration due to gravity is $10m{s}^{-2}.$ Then, What is the specific energy (approximate)?

• A. 0.3
• B. None of these
• C. 2.5
• D. 2.3

Answer 1

The correct option is D 2.3

We know that
Q = AV
$\Rightarrow$ 30 = 6 $\times$ 2 $\times$ V
$\Rightarrow$ V = 2.5 m/s
The specific energy may be given as

$E=y+\frac{V_1^2}{2g}$

$=2+\frac{{\left(2.5\right)}^2}{2\times 9.81}=2.3m$