Question

Water flows at 10 m3/s in a 5-m-wide channel. What is the height of a suppressed rectangular (sharp-crested) weir that will cause the depth of flow in the channel to be 2 m

Answer 1

Hw = 1.01 meters

Step-by-step explanation:

Given data:

flow rate = 10 m^3

depth of flow in channel = 2 m

Determine the height of a suppressed rectangular weir ( Hw ) using the following expressions

expression for the elevation of of water surface above crest of weir

H = 2 -
`H_(w)` ------ ( 1 )

expression for the height of the weir ( Hw )

Hw = 2 -
`( (Q)/(C_(w) b)) ^{(3)/(2) }` ---------- ( 2 )

expression for the weir coefficient ( Cw )

Cw =
`(2)/(3) C_(d) √(2g)` -------------- ( 3 )

expression for the coefficient of discharge ( Cd )

Cd = 0.611 + 0.075
`(H)/(Hw)` ---------- ( 4 )

Finally to determine the value of Hw we apply the trial and error method

in the trial and error method the value of LHS = RHS for the number chosen to be true