What physics study path would help me answer my own hydraulics question?

[pvshackguy]

TL;DR

What physics study path would help me answer my own hydraulics question?

I have a water pipe in an exposed location that is allowed to drain when not in use. The vertical drop between the top and bottom of the pipe is fixed, as is the horizontal distance between the ends.

If the pipe does not drain properly after use, it will freeze and burst in winter, so any downwards dip along the run of the pipe is unacceptable.

I am wondering whether, for quick and reasonably complete drainage, a linear slope or a curved path would be optimal. However I'd prefer not to be handed the answer.

What I'd really like to know is what course of study would be needed, for a well-aged gent who took Canadian high school physics late in life by correspondence (quaint?) to know enough to answer this question for myself.

 

[.Scott]

Here are the "concepts of concern".
A thin coating of water will not readily flow, so you are looking for either a very thin coat that will readily evaporate or "beading" to form clumps of water that will descend the slope.
You're going to be dealing with surface tension and hydrophilic/hydrophobic surfaces. Of course, gravity is the main mover, but you have likely mastered that part.

When I ask Google AI "What college courses deal with surface tension and hydrophilic surfaces?", it responds with:

College courses covering surface tension and hydrophilic surfaces often focus on material science, fluid mechanics, and physical chemistry, focusing on wetting, capillary action, and surface energy. Key courses include Surface Chemistry, Advanced Fluid Mechanics, Materials Science, and Biomedical Engineering, where topics like capillary behavior, surfactant function, and contact angles are studied.

 

[pvshackguy]

So, an afternoon's casual read I take it.
Cheers, much appreciated.

 

[gmax137]

For practical problems such as this, I would recommend you look at fluid flow textbook for mechanical engineers.
EDIT: do a search on 'fluid flow pdf' to find a bunch of class notes. Scan thru them till you find one you like.


An alternative would be Crane 410, a completely practical guide. "Flow of Fluids Through Valves, Fittings, and Pipe (Technical Paper No. 410)"

Wow, scratch that, I just looked on Amazon and used copies are $120 and up. I paid $8 for mine, direct from Crane valve company (in 1987, lol). If you are near an engineering school you might find a copy in a used bookstore.

Sorry for that diversion. Your particular pipe:
is it open at both ends?
diameter?
length?

 

[kuruman]

I assume that the pipe is supposed to drain under gravity. Based on the idea that the less time the water spends in the pipe the less likely it is to freeze, I would recommend researching the brachistochrone which literally means "shortest time" in Greek. Of particular interest is that a ball released at the top of a brachistochrone track will take the same time to reach the bottom as a ball released at any point in between.

The web has lots of videos, simulations, the math background and suggestions on how to draw and construct one. Should you choose to go that route, I will be curious to hear how it played out.

 

[Baluncore]

I am wondering whether, for quick and reasonably complete drainage, a linear slope or a curved path would be optimal. However I'd prefer not to be handed the answer.

Then you need to get back to your first childhood, to play with water in clear plastic tubes, and to make a siphon. Your second childhood will be here shortly, and then they will not let you play with water.

There are two different fluids involved, flowing in different directions. The water must flow down the pipe, so the air, to displace it, must flow up the pipe.

You assume the pipe or conduit must be dry, yet the pipe only has to be half empty, or less, everywhere. Only a full pipe, or chamber, will crack when frozen.

You need to study flow in both a closed channel, and a partially filled channel.
https://en.wikipedia.org/wiki/Pipe_flow
https://en.wikipedia.org/wiki/Siphon
https://en.wikipedia.org/wiki/Flow_in_partially_full_conduits

 

[pvshackguy]

I assume nothing.

Thanks for your post.

The pipe in question is in place and working; has been for many years. However I did have to fix it a couple of times early on, as at -35 or -40 C there is no time to waste emptying it out.

I'm keen to continue my education until my brain falls out. I anticipate retiring in the not too distant future - hopefully while I'm still breathing - so more time will be available for such activities. I was curious as to how far removed I am from having a better understanding of the principles dictating the performance of a particular piece of amateur plumbing.

 

[pvshackguy]

For practical problems such as this, I would recommend you look at fluid flow textbook for mechanical engineers.
EDIT: do a search on 'fluid flow pdf' to find a bunch of class notes. Scan thru them till you find one you like.


An alternative would be Crane 410, a completely practical guide. "Flow of Fluids Through Valves, Fittings, and Pipe (Technical Paper No. 410)"
View attachment 369332
Wow, scratch that, I just looked on Amazon and used copies are $120 and up. I paid $8 for mine, direct from Crane valve company (in 1987, lol). If you are near an engineering school you might find a copy in a used bookstore.

Sorry for that diversion. Your particular pipe:
is it open at both ends?
diameter?
length?

No apology necessary. A relatable bit of humour.

The 1/2" pipe is connected at both ends to hoses when in use, then disconnected at the bottom to let the pipe and the upper hose drain out. Approx length 8 m. Vertical delta maybe 1m.

But as I explained elsewhere, the "system" (to elevate a hack) works fine. Otherwise I would run out and get you better measurements. I've just always wondered if the curve I arrived at could be improved upon, and what knowledge would be required to figure that out.

Retirement looms and I look forward to having more time to study for its own sake.

 

[jrmichler]

TL;DR: What physics study path would help me answer my own hydraulics question?

What I'd really like to know is what course of study would be needed, for a well-aged gent who took Canadian high school physics late in life by correspondence (quaint?) to know enough to answer this question for myself.

High school physics has everything you need except for fluid dynamics. Fluid dynamics is a third year engineering course. Lots of fun reading in between.

Then you need to get back to your first childhood, to play with water in clear plastic tubes, and to make a siphon. Your second childhood will be here shortly, and then they will not let you play with water.

Which leads to what @Baluncore said. I would have liked to say something similar, but his words are much better than anything I would have written.

I am wondering whether, for quick and reasonably complete drainage, a linear slope or a curved path would be optimal. However I'd prefer not to be handed the answer.

Be careful. A brachistochrone path is best for a frictionless object. That does not mean that it is best for a liquid. It only needs to drain down before it freezes solid. A film of ice on the inside of the pipe will melt when next filled with water. Pipe insulation will give more time.

Are you SURE you don't want me to hand you the answer? If you do, I need some more details. Does this line drain automatically, or is it a manual operation? How long a line? What is the vertical distance? Is it under pressure when filled?

 

[berkeman]

The pipe in question is in place and working; has been for many years. However I did have to fix it a couple of times early on, as at -35 or -40 C there is no time to waste emptying it out.

How did you fix it? Was the damage obviously from ice expansion bursting the pipe? If so, was the pipe clogged so not free-flowing to drain?

 

[Herman Trivilino]

TL;DR: What physics study path would help me answer my own hydraulics question?

What I'd really like to know is what course of study would be needed, for a well-aged gent who took Canadian high school physics late in life by correspondence (quaint?) to know enough to answer this question for myself.

Hmmm... That's a tough question. To investigate on your own you need a college-level introductory physics background before you can dig into hydraulics.

I think you've already answered your own question:

any downwards dip along the run of the pipe is unacceptable.