Question

A hydraulic jump occurs in a 4 m wide rectangular channel carrying a discharge of 5 cumec at a slope of 0.004, the depth of flow after the jump is 1.2 m. What is the depth of flow before the jump ?

• A. 0.20 m
• B. 0.50 m
• C. 0.60 m
• D. 0.40 m

Answer 1

The correct option is A 0.20 m

Given, B = 4m, Q = 5 cumecs, S = 0.004

$y_2=1.2m$

$F_2=\frac{V_2}{\sqrt{g{y}_2}}=\frac{Q_2}{B{y}_2\sqrt{g{y}_2}}$

$=\frac{5}{4\times 1.2\sqrt{9.81\times 1.2}}=0.303$

$y_1=\frac{y_2}{2}[\sqrt{1+8F_2^2}-1]$

$=\frac{1.2}{2}[\sqrt{1+8\times (0.303{)}^2}-1]$

$=0.19m$