Fluid Mechanics - Syphoning Water

Bernoulli's equation used to explain a common phenomena in syphoning water.

Gaussian Math Fluid Mechanics module, situable for those studying it as an undergraduate module.

Check out www.gaussianmath.com for an indepth study with downloadable notes or for more math related content.

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[canman5060]

Do you also assume the friction between the moving water and the syphoning pipe is negligible ?

[donylee]

Yes of course friction is negligible in this case. When you consider friction, you need to analyze the energy loss using a certain 'Energy Equation', an extension of the Bernoulli's equation I believe.

All this is in another section called pipe analysis, which unfortunately I have no videos on it.

[21Wook75]

Assume that loss of head in friction per metre is 0.5v^2/2g where v = velocity in pipe.

Note: 0.5v^2/2g is 0.5 times velocity head

This is the whole question along with my previous comment.

Does anyone know how to work out limiting velocity of water in pipe and depth of water in tank when siphon action ceases for this question?

[21Wook75]

Water is siphoned out of a tank by means of a bent pipe ABC 24m long and 25mm diam. The end A is below the water surface and 150mm above base of tank. The length AB is vertical and 9m long and BC is 15m long with discharge end C 1.5m below base of tank. Assuming a barometric pressure of 10.3m of water and that siphon action at B ceases when absolute pressure is 1.8m of water, determine limiting velocity of water in pipe and depth of water in tank when siphon action ceases.

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[rohbit]

Hey Dony,

At point C, why is it that we choose the pressure to be 1 atm and not PB, the pressure inside of the pipe? That's the only thing that puzzles me. What's a good way to think about it?

- Reuben

[bubzieboo27]

its awesome like in content but i wish u could have spoken a bit slower..

[jsantoyoc]

Cheers sir...its been a quick brush out of science...JC UK

[godinzoom]

very very helpful! thanks a lot donylee! cheers from the philippines!

[kasuskasus]

Do you ever enjoy simply watching water? Or do you always have to understand, break down, analyze it?

[7oota2007]

hi , that was really help full. but i have a q

we assumed that Vc is much greater than Va , but you said the flow on Vc compared to Va is very slow. how is Vc greater Than Va then ?

[heramban]

what if the pipe is horizontal?

[canman5060]

Thanks.