Question on flow rates over a weir.

[jason_mcc]

Homework Statement

Hi everyone. All help is appreciated.

The discharge over a rectangular notch is to be 0.14m³/sec when the water level is 0.23m above the sill. If the coefficient of discharge is 0.6 calculate the width of notch required.

Answer: 0.716m

Homework Equations

I think it is Q=\frac{2}{3}b\sqrt{2g}H^{\frac{2}{3}}C_d

where Q=flow rate, H=height of water level above bottom of notch, b=width of notch.

The Attempt at a Solution

Q=\frac{2}{3}b\sqrt{2g}H^{\frac{2}{3}}C_d

0.14=\frac{2}{3}b\sqrt{2g}0.23^{\frac{2}{3}}0.6

0.14= 2/3 x b x 4.429 x 0.375 x 0.6

0.14= 0.664 b

b= 0.21m

which is wrong. Anyone know what I'm doing wrong?

 

[nvn]

jason_mcc: There is a typo in your given relevant equation. Change H^0.66667 in your relevant equation to H^1.5.

 

[jason_mcc]

jason_mcc: There is a typo in your given relevant equation. Change H^0.66667 in your relevant equation to H^1.5.

Thanks, got it now.