intro

Discussion in 'New Members' started by tonyv, 15 Jul 2009.

  1. tonyv

    tonyv

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    Just to say hello!
    Also , I would like to ask if anyone knows if the following information is sufficient to calculate the flow rate over a weir?
    (a) weir width
    (b) Height of waterfall
    (c) Distance out from base (where the water hits the base)
    Thanks
     
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  3. mnd123

    mnd123

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    Welcome to the forum

    thats far too technical for me - sorry mate! Just a welcome at this point ;)
     
  4. RiaanP

    RiaanP Moderator

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    Hello and Welcome Tony

    I would rather think the return pump size will give the flow rate over the weir.

    You can only "overflow" the same amount as what you "return"

    Only option that will have an impact you listed is the width.
     
  5. crispin

    crispin

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    hey there tony, welcome to MASA, great to have you here.

    thats a rather tough question first up, but do you want to know the rate of water flowing over a weir and how to calculate it (and if so why??? :))?

    i would actually look at asking an hydrolics engineer as they will have calculations of river flows over water weirs, but its a technical quetion which falls well outside my knowledge base:)
     
  6. RiaanP

    RiaanP Moderator

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    Actually the answer is really simple.

    Look at dams
    The width or damwall got nothing to do with the water flow rate. It is more the amount of water entering the system. During low rainfall the HEIGHT of the water over the overflow is low (if any). During heavy rainfall periods, the height of the water over the wall increases and the dam is overfull. That is why a dam can be 105% full.
    Doubling the width of the damwall, will halve the height of the overflow.

    The same with your tank. It depends on the volume entering the display tank, so it is fully dependant on the return pump size.

    Now the real question should be: for a return pump that delivers 2000L/h at my tank top, and you want the height/thickness of the water above the weir to be 5mm, what must the width be?

    Somewhere I saw this calculation, but where I do not know.
     
  7. Tony

    Tony

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    Hello and welcome
     
  8. inflames

    inflames

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    welcometomasa
     
  9. riyadhessa

    riyadhessa

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    tonyv...Welcome to MASA
     
  10. jacquesb

    jacquesb Retired Moderator

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    A VERY WARM WELCOME to MASA, TonyV. Great to have you on-board!

    You should get a few more decent answers as well. My opinion is the same as what RiaanP said: what you put in, is what you will get out.
    So - your return pump will determine the amount of water flowing down your downpipe/overflow.....
     
  11. Tobes

    Tobes Retired Moderator

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    Welcome to MASA Tonyv, hope you enjoy your stay with us. Do you have a tank? If yes, would you mind sharing more with us? How long it's been running, how long you're in the hobby etc etc. Better still - some pics???

    :wave2:
     
  12. crispin

    crispin

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    a weir and a spillway are ummmmm different things:) weirs are used in rivers, dam walls hold water and have a spill way, or sluice gates to take the excess water.
     
  13. RiaanP

    RiaanP Moderator

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    Yes, agreed Crispin.
    Just trying to show the concept. Take a dam wall (where water goes over) or river weir or overflow box. The amount or volume of water is dependant on the flow entering the system.
    Less in-flow, less and lower overflow
    More in-flow, more and higher overflow.
     
  14. Jaak

    Jaak

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    Welcome to MASA!!
     
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