Question

The flowrate through a rectangular channel is 20 cfs. The upstream width of the channel is 10 ft, and the depth of the water in the channel is 1 foot. Will there be a jump down stream?
a. Yes
b. No

Answer 1

To solve this problem we will use the Froude number that relates the Forces of Inertia with the Forces of Gravity. There will be jump in the downstream only if Froude Number (Fr) is greater than 1 at upstream. Our values are given as,

$Q = 20cfs\\w= 10ft\\D= 1ft$

Then the velocity would be:

$V = \frac{Q}{wD}V = \frac{20}{10*1}V = 2ft/s$

The number of Froude is given as,

$Fr = \frac{V}{gD}^{1/2}$

Where,

V = Velocity

g = Gravity

D = Diameter

Replacing we have that

$Fr = \frac{2}{32.2}^{1/2}\\Fr = 0.352\\Fr$

There will be no Jump, correct answer is B.