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I am planning to investigate the effect of bend curvature of a pipe on velocity of water. For this, I will need to find the velocity of water through various pipe bends. Would placing an object in the water such that the objects velocity can be measured and equated to the waters velocity do the trick?

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  • $\begingroup$ is it possible for you to interrupt the stream of water leaving the piping system experiment and catch it in a bucket? If so you can then time how long it takes to accumulate a gallon of water in the bucket- and then, knowing the pipe diameter, calculate how fast the water needs to flow through a pipe that size in order to achieve the gallons-per-minute rate you measured. Simple, foolproof, no instrumentation, cheap and accurate... $\endgroup$ – niels nielsen Dec 25 '18 at 8:17
  • $\begingroup$ Bernoulli's equations should help. $\endgroup$ – QuIcKmAtHs Dec 25 '18 at 8:26
  • $\begingroup$ Are you trying to measure the velocity variation over the cross section of the pipe, or just the average velocity? Water is basically incompressible, so, as long as the diameter is the same in the bends as in the straight sections, the average velocity will also be the same. The volumetric flow rate is not affected by the presence of the bends. $\endgroup$ – Chet Miller Dec 25 '18 at 13:15
  • $\begingroup$ I am trying to measure the velocity variation over a cross section and analyse how the velocity varies when the water passes through various bends. $\endgroup$ – user217995 Dec 26 '18 at 6:54
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I assume you want to see the velocity profile and not just the average velocity?

If so a common method (used for all the photos in Tritton) is to introduce a small particle/dye into the fluid. If you have see-through pipes you can quite easily caluclate the velcity of the particle/dye. You can then change the radius at whoch it gets introduced to see the velocity profile.

In order to stop turbulance I would recommend a slow or viscous fluid (low reynolds number), do you know about dynamical similarity?

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  • $\begingroup$ I am not familiar with dynamical similarity. However, I just have to calculate the displacement and time of the particle to find the velocity right? or is there something else to that? Also, can you please elaborate on how the radius at which it gets introduced? $\endgroup$ – user217995 Dec 26 '18 at 6:38
  • $\begingroup$ Yes. If you want to look up more detail its called Reynolds experiment. Basically, the fluid flows faster in the center of the pipe than at the edges due to friction, by putting the particle in at different radii you can measure this difference. There is a good chance however, the flow will be turbulent and so the motion of the particle will be random. If you just want avergae flow, just time how long it takes a small object to go through the whole length. $\endgroup$ – Toby Peterken Dec 27 '18 at 18:01

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