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A question in fluid about an experiment

  1. Sep 3, 2012 #1
    Hi, I asked for help in such problem before but could get what satisfied me, so I'm here for your help again.

    I'm doing an experiment at home, I have pump with maximum flow rate of Q and maximum head of H, I'm using a pipe of D1 diameter and L1 length to connect the pump to a nozzle of D2 diameter, here is my question "for how many meters the water will be tossed from the nozzle in terms of Q, H, D1, L1, D2 ?".

    also I want to know if I put a solenoid valve just before the nozzle how much is the pressure if the solenoid valve is once closed and other opened.

    I tried to solve the problem in such a way, so please also have a look on it on this link post 1 & 4.

    I'm and electronic engineer and have a little background in fluid, so I'll appreciate your help.
  2. jcsd
  3. Sep 3, 2012 #2


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    Gold Member

    For starters, lets look at the punp.
    Maximum Q occurs when the pump exit has no pressure.
    Maximum head occurs when Q = 0.
    So you cannot have maximum Q and maximum H at the same time.

    The pressure at the nozzle is determined by the pressure drop in the pipe. The pressure drop in the pipe is determined by the Q ( or fluid velocity ) . You will not get pump pressure at the nozzle. a longer and smaller diameter pipe has greater loss than a shorter and larger diameter pipe.

    Nozzle: quoting russ from the link "The height the water will go to is a function of the pressure at the exit only. The pressure determines the velocity, which determines the height."

    So what you have to do is pick a Q. Determine the losses in the pipe. that determines the pressure at the nozzle, which will give you the height of the nozzle flow. You might have to iterate to get the desired Q and h at the nozzle.
  4. Sep 3, 2012 #3
    I was ganna say pretty much what 256bits said, but he put in a lot more effort than I was oging to, but you can't get an answer better than that. The only thing left to do is shove the equations into Matlab and use fsolve or some form of Newton's method.
  5. Sep 3, 2012 #4
    Thanks for your replay 256bits, I get a good idea now about the problem, but I still have a question, let us say that I need the height of the nozzle flow be 1m, then I understand that 1m of height mean a specific pressure at the nozzle which determine the losses in the pipe and finally we solve for the Q, here is my question, how can I calculate: the pressure at the nozzle, the losses in the pipe and how to make the pump operate at specific Q that will give the desired height.

    suppose the nozzle has length of L1, and D1 of diameter, where the pipe has L2 of length and D2 of diameter.

    thanks in advance.
  6. Sep 8, 2012 #5
    Hi, I asked for help again but no one replayed, please help.
  7. Sep 9, 2012 #6
    Look up Bernoulli's principle. That's what you need.
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