Question

The sequent depth ratio in a hydraulic jump formed in a rectangular horizontal channel is 10. The Froude number of the supercritical flow is

• A. 10.4
• B. 12.2
• C. 7.42
• D. 4.21

Answer 1

The correct option is C 7.42

$\begin{array}{cc}\frac{y_2}{y_1}& =10\\ \frac{y_2}{y_1}& =\frac{1}{2}[-1+\sqrt{1+8F_1^2}]\\ 10& =\frac{1}{2}[-1+\sqrt{1+8F_1^2}]\\ 20& =-1+\sqrt{1+8F_1^2}\\ 21& =\sqrt{1+8F_1^2}\\ 441& =1+8F_1^2\\ 8F_1^2& =440\\ F_1& =\sqrt{\frac{440}{8}}=7.42\end{array}$