Practice Question: Estimating Flow Rate in Open Channel at Critical Velocity

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Solution

For a rectangular open channel, critical velocity is given by:

\[v_c=\sqrt{gy_c}\]

Therefore, critical depth, yc 

\[y_c=\frac{v^2_c}{g}\]

 

\[y_c=\frac{8^2}{32.2}\approx 2\ ft\]

Flow area:

\[A=by_c=12\times 2=24\ ft^2\]

 

Flow rate:

\[Q=VA=8\times 24=192\ \frac{ft^3}{sec}\]

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