1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Question on flow rates over a weir.

  1. Jan 2, 2009 #1
    1. The problem statement, all variables and given/known data

    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


    2. Relevant equations

    I think it is Q=[tex]\frac{2}{3}[/tex]b[tex]\sqrt{2g}[/tex]H[tex]^{\frac{2}{3}}[/tex]Cd

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

    3. The attempt at a solution

    Q=[tex]\frac{2}{3}[/tex]b[tex]\sqrt{2g}[/tex]H[tex]^{\frac{2}{3}}[/tex]Cd

    0.14=[tex]\frac{2}{3}[/tex]b[tex]\sqrt{2g}[/tex]0.23[tex]^{\frac{2}{3}}[/tex]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?
     
  2. jcsd
  3. Jan 2, 2009 #2

    nvn

    User Avatar
    Science Advisor
    Homework Helper

    jason_mcc: There is a typo in your given relevant equation. Change H^0.66667 in your relevant equation to H^1.5.
     
  4. Jan 2, 2009 #3
    Thanks, got it now.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?