1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Fluid dynamics

  1. May 23, 2014 #1
    1. The problem statement, all variables and given/known data

    Water flows at the end of an aqueduct into the upper end of a 500m long pipe. The pipe has angle of 30 degrees to the horizontal and its low end exits into the bottom of a collection tank. The collection tank can hold a depth of 120m, above the centre line of the delivery pipe exit. Extra liquid can overflow the lip of the tank into a river.

    The pipe tapers from a diameter of 2.0m at the top to 0.8m at the bottom. Assuming the head loss to be 8% of the potential head of the wateras it enters the pipe, determine the flow velocity of the water as it enters the collection tank.

    I have worked out two CSA's for the pipe and are stuck. Should I use bernoulli's equation or the continuity equation to work out the flow velocity of the water?

    2. Relevant equations



    3. The attempt at a solution

    A1=πd^2/4=πx2^2/4= 3.142 m^2
    A2=πd^2/4=πx0.8^2/4= 0.503 m^2

    I have got the CSA's but don't know whether to use bernoullis equation or the continuity equation to find the flow velocity.
  2. jcsd
  3. May 23, 2014 #2


    User Avatar
    Science Advisor
    Homework Helper
    2017 Award

    You wrote a continuity equation and the Bernouilli equation. That's two (I omit Q) for two unknowns: C1 and C2. Continuity says C1 = C2 A2/A1. Leaves 1 unknown, C2. How about filling in the knowns in the Bernouilli equation expressed in C2 ?

    Must say I find the exercise formulation somewhat vague. Or is it a part of a sequence?
    Is the collection tank empty or full in this part ? makes a difference for p2 !
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted