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I Density Siphoning?

  1. Oct 25, 2017 #1
    Hi guys,

    got a little problem i'm currently working on and looking for some input/sanity check.

    Firstly i have a round tank within a round tank both with open tops, the inner tank is suspended within the outer tank such that there is a gap between both tanks bottoms faces, the inner tank open top is lower than the outer tank top opening such that a head difference is present to encourage siphoning through a transfer pipe in the middle of the inner tank.

    the outer tank is 3/4 full of a fluidized sand and 1/4 water on top which overflows, the inside tank has a transfer pipe in the center of its bottom face to allow the transfer of fluidized sand, the length of this pipe is half way above the mid line of the outer tank and the top of the inner tank is 500mm lower than the top of the outside tank, thus 500mm head difference.

    so with the sand at 0.75h and the height of the open end of the transfer pipe on the inner tank being roughly 0.5h my question is will the fluidized sand try to equal its level between the inner and outer tank, thus creating a flow until the two fluidized sand teeter beds are level in both tanks?

    i cannot seem to find a similar example with formula which i can use to calculate what may happen.
  2. jcsd
  3. Oct 26, 2017 #2


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    Please provide a sectional diagram showing the initial position of sand and water.
  4. Dec 6, 2017 #3
    Sorry i had forgot about this problem, take a look at the crude excel drawing which shows the tank setup, with an updated description.

    Z1 being the outer tank height half filled with liquidized sand on the bottom and water on the top, Z2 being the inner tank which the material will transfer to, and the transfer pipe with height Z3 but length of Z4.

    the liquidized sand level will be at height Z5 and be liquidized by a flow of water in the direction of the arrows, the inner tank will also have an flow upward.

    Will the sand transfer even though Z3>Z5?

    I'm also guessing that the flow upwards in the outer tank will be V1 but the inner tank will be a combination of V1 & V2?

    With this problem it makes sense to me that the sand will not flow as there is no head difference for the sand to transfer up to the height of the transfer pipe exit? but would a drop in the height of the top of the inner tank create a siphoning effect that would overcome this head, and would it be proportional I.E if the

    Last edited: Dec 6, 2017
  5. Dec 6, 2017 #4


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    What text is hidden behind the diagram?
  6. Dec 6, 2017 #5
    i'm not sure i understand?
  7. Dec 6, 2017 #6


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    The text ending in "I.E if " indicates a possible question but there is no end to the sentence and no question mark.
    It looks to me like the end part of the posted text was not copied, or was covered by the picture.
  8. Dec 6, 2017 #7
    Sorry, i meant that would the reduction of the height of the inner tank (Z2), thus creating a head difference between the inner and outer tanks, be proportional to reducing the height of the transfer pipe (Z3) to a level that was equal to or less than the height of the sand (Z5).

    i'm finding it hard to nail down with calculations what exactly may happen, i can assume but id rather have something to back up these assumptions, perhaps there is another way of drawing the same system such that a solution is clearer?
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