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Homework Help: Orifice equation check pls

  1. Dec 6, 2008 #1
    1. The problem statement, all variables and given/known data

    How much water will flow through a hole with diameter 1cm?we have a tubular container, water column 10 meters high- at the bottom is a hole with a diametr of 1 cm. the tube is constatly being refilled so the height of the water column remains the same - 10 meters.how much water per minute will flow through the hole having in mind the pressure the water above will exert on the small hole? please give me an answer in liters.

    3. The attempt at a solution

    Q=Cd * A * (2g * H)^0.5

    Q = flow (cms)

    Cd = Coefficient of Discharge (use 0.6, this is the generally accepted value)

    A = area of orifice (m^2), this would be pi*r^2 = pi*(0.005m)^2

    g = gravitational constant (9.8 m/sec^2)

    H = head (or height of water) above centerline of orifice = (10-0.005)m

    Q = 6.602 x E-08 * 60sec/min

    Q = 4.00 x E-06 m^3/min

    1 liter = 1 dm^3

    Q = 4.00 x E-06 m^3/min * 1000 dm^3/m^3

    Q = 4.00 x E-03 liter/min


    Q = 0.004 liter/min

    have i done the calculations right? what is your answer in liters/per second?
  2. jcsd
  3. Dec 7, 2008 #2
    The formula is fine, but I get different numbers from it. Try putting everything in SI units to obtain the flow in cubic meters per second, and then convert the result to whatever other units you need.
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