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Fluid Mechanics

  1. May 22, 2016 #1
    1. The problem statement, all variables and given/known data
    A hot oil(specific gravity = 0.7) flows through a pipe of 4 cm internal diameter, at a velocity of 0.2 m/s. Determine:

    i) The volumetric flow rate of the oil discharged from the pipe.
    ii) The mass flow rate of the oil discharged from the pipe.
    iii) If the pipe discharges the oil to a tank of 3 m^3 volume, how long does it take to fill the tank?
    iv) If the force applied to the pipe inlet due to the oil flow is 20N, find the inlet pressure.

    The attempt at a solution:

    i) Volumetric flow rate: Q=vA
    A= πr^2 --> A= π*0.02^2 = 1.257*10^-3 m^2
    Q= 0.2*1.257*10^-3= 2.514*10^-4 m^3/s

    ii) Mass flow rate: m=ρQ
    Specific Gravity : SG=ρ(oil)/ρ(water) -> ρ(oil)=SG*ρ(water) -> ρ(oil)= 0.7*1000= 700 kg/m^3
    m= 700*2.514*10^-4 = 0.18 kg/s

    iii) ?

    iv)Pressure= force/area -> P=20/1.257*10^-3 = 15910.89Pa = 16kPA

    Hi, I am having tough times trying to solve this question. If You find it easy please teach me! Any help will be greatly appreciated! Because i can't seem to wrap my head around this question :(
  2. jcsd
  3. May 22, 2016 #2
    You have gotten the same answers I got. I think you may have it!
  4. May 22, 2016 #3
    Thank you! But what about the time it takes to fill the tank?
  5. May 22, 2016 #4


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    Staff Emeritus
    Science Advisor
    Homework Helper

    That should be the easiest one of all to figure.

    Look, if you put X cubic meters per second into a tank which has a total capacity of Y cubic meters, what amount of time does this take?

    After 1 second, there is X cubic meters in the tank; after 2 seconds, there is 2X; etc., etc. Rinse and repeat until you have accumulated Y cubic meters.

    You should be able to solve this using the dimensions of the quantities alone.
  6. May 23, 2016 #5
    Thank you! i thought there was more to it than that
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