Pressure in a straight pipe vs a curved pipe?

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    Pipe Pipes Pressure
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Discussion Overview

The discussion revolves around the pressure differences in a straight pipe compared to a curved pipe, focusing on fluid dynamics principles. Participants explore theoretical implications, practical applications, and the effects of pipe geometry on fluid flow and pressure readings.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant suggests that pressure readings at the bottom of both pipes would be the same if the pipes are sealed, full, and at equilibrium, referencing the formula for pressure as density times gravity times height.
  • Another participant agrees, noting that friction only becomes significant when there is flow, implying that in a static situation, pressure should equalize.
  • A different viewpoint is presented regarding the implications of differing pressures, suggesting that if the pressures were not equal, it could lead to violations of conservation of energy, reinforcing the idea that pressures must be the same.
  • One participant introduces the concept of G-forces affecting pressure in bent pipes, questioning how this might influence the overall pressure readings.
  • Another participant mentions the practical implications of curved pipes, stating that they can lead to reduced throughput and that minimizing bends is preferable in design.
  • A participant raises a question about the advantages of slightly curved pipes over L or T junctions, considering factors like cost and structural integrity.
  • Another participant emphasizes that friction from bends and joints in pipes reduces flow, advocating for minimizing bends and maximizing radii for better performance.

Areas of Agreement / Disagreement

Participants express a mix of agreement and differing opinions regarding the effects of pipe curvature on pressure and flow. While some agree on the static pressure readings being the same, others introduce additional factors like G-forces and friction that complicate the discussion. No consensus is reached on the overall implications of these factors.

Contextual Notes

Participants acknowledge that the discussion involves assumptions about the conditions of the pipes (e.g., whether they are sealed, full, or in flow) and the effects of friction, which may not be fully resolved. The discussion also touches on practical considerations that may not directly relate to the theoretical aspects of pressure in curved versus straight pipes.

Who May Find This Useful

This discussion may be of interest to individuals involved in fluid dynamics, engineering design, plumbing, or those seeking to understand the practical implications of pipe geometry on fluid flow and pressure.

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Hi everyone. My dad was debating with his friends over something, and he asked me for my opinion too. I've been on these forums before so I thought I'd ask here.

So let's say you have two pipes. Both have the same cross-sectional area, same fluid inside, and they both extend to the same height at the top. However, one is straight and one curves around a bunch like a snake. If we stick a pressure gauge at the bottom of both, will the readings be the same?

It's been years since I've taken physics, but I remember the formula for pressure in this case was like density*gravity*height. In that case, wouldn't it be the same for both pipes unless you count the whole length of the curved one? Even though his friends argued that way, it just doesn't seem right. I'm guessing there's some more complicated stuff involved besides just that simple equation.
 
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It will be and you have the correct formula. Provided that the pipe is sealed and full and there is no flow, the friction will not play a part. When you have flow, that is when friction plays a part. That is why sometimes when you turn a tap on it starts off at high pressure and then decreases because there is too much friction in your line.
Edit: also, when you close a tap it can take a time to build pressure again, but when its at equilibrium, it will show the same dead head pressure.
 
Consider what would happen if the pressure was different. You could connect the two pipes together at the bottom and the increased pressure in the curved pipe would push water up the straight one. If you also connected them at the top the water would flow round and round. You could insert a turbine and extract some energy. In short you could violate conservation of energy. That's not possible so the pressure must be the same.
 
I think there is a G force added to the equation when the pipe is bent? What do you think?
 
There's definitely a drop in throughput due to curved pipes. You want as few elbows as practical, and what ones you do use, should be as large a radius as practical.

This sure plays into how I connect up my pool filter and heater.
 
The same as if you compare the pressure at the bottom of a glass of water, with the pressure at the bottom of a kiddie's swimming pool filled to the same height as that in the glass.

Or standing in the middle of a kiddie pool, with walking out a few feet into the ocean surf.
 
tomdaily said:
I think there is a G force added to the equation when the pipe is bent? What do you think?
Are you aware that this thread has not been visited for almost 5 years, and the OP hasn't been to Physics Forums since 2016?
 
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D'oh! Got sucked in!
 
Wait - so I am doing some "POOL" network research - and was thinking about flow and trying to remember my physics and decided to google TODAY (funny I stumble on this today after you all did yesterday)

My question is - are slightly curved pipes (made by heating and bending) better than L or T junctions? Or are there other reasons to "curve" them (other than to get over each other) as opposed to using junctions? (like maybe it's cheaper using heat and less likely to break than installing a junction??)Thanks

(--- someone that writes stuff for TV and is looking for some great real answers---)
 
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Anything that causes friction in a pipe will reduce the flow.

Sharp bends are bad.
All those glued joints are a problem, too, but can't really be avoided.

So, as far as practical:
- minimize bends
- maximize radii of bends
- minimize unnecessary joints

Sure, long, straight pipes, bent into shape, would reduce friction - but probably not practical, so not necessarily advisable as general advice.
 
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