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Flow in branching pipe

  1. Mar 10, 2016 #1
    1. The problem statement, all variables and given/known data
    what does the author mean by if P is below the surface of B then h2 and Q2 are both 0 ?

    2. Relevant equations


    3. The attempt at a solution
    at the last second line from the bottom , the author gave if P is below the surface of B then water must be out of B and Q1 +Q2 = Q3 ? both statement are contrary to each other
     

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  3. Mar 10, 2016 #2

    haruspex

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    h2 might be a typo for d2?
    It might help if you would define Li and di. Qi is volume flow rate, I gather.
     
  4. Mar 11, 2016 #3
    which h2 is typo for d2 ?
     
  5. Mar 11, 2016 #4

    haruspex

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    In your post, you quoted a line from the second attachment referencing h2. There is no other h2 in either attachment. I am suggesting the h2 in the attachment might be a typo for d2.
     
  6. Mar 11, 2016 #5
    what does h2 mean actually ? why it will = 0 ?
     
  7. Mar 11, 2016 #6

    haruspex

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    I don't know, but I might be able to figure it out if you answer the questions I posed in post #2.
     
  8. Mar 20, 2016 #7
    refrerring to the notes in post 1 , the author said that when P is above the surface of the resevoir B , then water must flow into B and Q1= Q2 + Q3 , why cant the the water from A and B flow to C ?, which is Q1 +Q2 = Q3 ?
     
  9. Mar 21, 2016 #8

    haruspex

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    Imagine closing off the point where the three pipes meet for the moment, so nothing is flowing. The pressure on the A side of that point will exceed the pressure on the B side. So when the joint is opened to allow flow, the A side will win.
    This all assumes no drag in the pipes. In the real world, some drag and a narrow pipe on the A side could mean that when water flows there is a large drop in pressure from the A reservoir to the junction, allowing water to enter the junction from B.
     
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