Answer
given,
width of trapezoidal channel, b = 6 ft
depth of water, d = 3 ft
discharge,Q = 250 ft³/s
now, we have to calculate Froude number
[tex]F_r = \dfrac{Q}{A\sqrt{gD}}[/tex]
Where D is the hydraulic radius
[tex]D = \dfrac{A}{P}[/tex]
[tex]F_r = \dfrac{Q}{A\sqrt{g\times \dfrac{A}{P}}}[/tex]
P is the width of the channel
P = b + 2 z d
P = 6 + 2 x 1 x 3
P = 13 ft
A = d(b + z d) = 3 (6 + 3) = 27 ft²
g = 32.2 ft/s²
now,
[tex]F_r = \dfrac{Q}{A\sqrt{g\times \dfrac{A}{P}}}[/tex]
[tex]F_r = \dfrac{250}{27\sqrt{32.2\times \dfrac{27}{13}}}[/tex]
F_r = 1.087
F_r > 1
Froude number is greater than 1 so, the flow is Super critical flow.
