I must clarify that I am not an engineer and I am not an engineering student. I am only doing a personal project in which I am stuck for months with the following problem, since my knowledge is not enough to answer it on my own! So I appeal to you:


You have the following system:

enter image description here

As can be seen in the drawing, what is sought is to transfer the blue fluid (water) to tank 2. For this the device consists of two very heavy pistons that will be used to transfer the fluid to tank 2.

The question is this: what weight must the pistons have to transfer water to tank 2 in a certain time? What equations should I use?

All the data is in the drawing.

  • $\begingroup$ So pressure is density * gravity * height , balance the piston mass and the height of its column of water against the height on the right... $\endgroup$
    – Solar Mike
    Jul 20 '18 at 5:12
  • $\begingroup$ The geometry will supply the pressure and the friction of the pistons and the flow will set the speed. $\endgroup$
    – KalleMP
    Jul 20 '18 at 21:46

From the diagram, the weight of both the pistons act in our favour(i.e. try to transfer water from the left to right tank).The opposing force is the weight of the vertical liquid column(60m) in the middle.So if the sum of the piston weights is more than the weight of the vertical liquid column, the water will be transferred from left to right.(This is neglecting the height of the water in the tanks since the height was not mentioned in the diagram).I think it is better to add a few known masses to the pison and relate the weight and the time taken to fill the tank istead of using analytical equations.


You can solve this problem by dividing the problem in three parts. We can consider Bernouli's equation for the horizontal parts, and for the vertical one we can use the formula $P = \rho \cdot g \cdot h$.

  • 1
    $\begingroup$ Welcome on the Engineering SE! See, how beautiful I made you post. :-) Typically, external references to support your statements are very welcomed here, similarly the Latex formatting of your text. :-) $\endgroup$
    – peterh
    Jul 23 '18 at 15:01

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