Fluid Mechanics Q: Find Vol. Flow Rate & Head Loss at C

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Discussion Overview

The discussion revolves around a fluid mechanics problem involving the calculation of volumetric flow rate and head loss in a pipe system with a leak at point C. Participants explore the application of Bernoulli's equation and the implications of given parameters such as friction factor and pipe diameter.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant expresses uncertainty about how to apply Bernoulli's equation at different sections of the system (AB, BC, etc.) to find the volumetric flow rate and head loss.
  • Another participant reports a calculated volumetric flow rate of 3535 L/s for a 22cm diameter pipe, questioning its plausibility.
  • Participants discuss the challenge of determining head loss in sections BC and CD without knowing the pressure at point C, particularly due to the leak.
  • There is a query about whether the pressure at C should be considered as a combination of velocity head and potential head, given the leak.
  • One participant suggests that if the height at C is unknown, the velocity head may be the only significant factor to consider.

Areas of Agreement / Disagreement

Participants generally agree on the need to consider both velocity head and potential head in their calculations, but there is uncertainty regarding the specific values and implications of the leak at point C. The discussion remains unresolved regarding the exact calculations and assumptions needed.

Contextual Notes

Limitations include the unknown height at point C and the implications of the leak, which affect the ability to determine pressure and head loss accurately. The discussion reflects a reliance on assumptions due to missing information.

morry
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Ok guys, here's a q from a past exam and I am not sure how to tackle it.
At point C, there is a leak and flow rate is given in L/s. I am also given the friction factor. I also know the diameter of the pipe.

The question asks for the vol. flow rate into the bottom tank. And then the head loss in BC and CD

What I am unsure of is the steps I need to take with Bernoullis equation. ie apply at AB then BC etc. I don't get that bit.

So if someone could point me in the right direction, Id be very happy.

Thanks.
 

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Ok, so I think I've calculated the volumetric flow rate, but it came out to be 3535 L/s, which is a fair bit for a 22cm diameter pipe.

I now have to find the head loss in BC and CD, but I don't know how to do this since I don't know the pressure at C.

Finally I have to sketch the hydraulic gradient, which I've never even heard of before.

Anyone have any ideas about these last bits?
 
Is the top reservior an open reservoir? Do you know the height at point C? That would mean that the pressure at C should be a combintation of the velocity head and the potential head at point C while the pressures at A and E are 0.

http://www.engineeringtoolbox.com/energy-hydraulic-grade-line-21_613.html

also, check out the definition on page 47 here:
http://www.engineeringtoolbox.com/energy-hydraulic-grade-line-21_613.html
 
Last edited by a moderator:
Both reservoirs are open to the atmosphere.

I don't know the height of C. Normally, finding pressure at C wouldn't be a worry, but this time there is a leak at C.

So would the pressure be the velocity head (With leak taken into account) plus potential head?

Thanks Fred!
 
Since it appears that that is the only information you have to go on, then I would say that you are correct. You should have some potential head, but if you are not given that information, then it might as well be considered insignificant. Velocity head is all you have left.
 
Cheers Fred.
 
Did it come out OK? Hope I helped.
 
Yeah came out eventually. :)

I think I've been letting the algebra get in my way, instead of letting my head look at the particular question. Hope there's an easy example of this question on the exam. :)
 

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