Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Aira1990 on 06/05/2007 15:42:39

Title: Inverted syphon of the roman aqueducts
Post by: Aira1990 on 06/05/2007 15:42:39

ok i'm doing this project for my physics class and it's on the roman aqueducts. at some points where there was a steep valley they would run a pipe down one side and up the other. how does this work?? an equation for this would be great and a source to cite even better but a general explanation would do nicely. i know it has something to do with pressure and that the side where the water enters the pipe is higher than the other. i can't find anything. HELP!  [???]   (the diagram is from http://www.facstaff.bucknell.edu/mvigeant/univ270_05/jake_aq/aqueducts.htm)

Title: Inverted syphon of the roman aqueducts
Post by: Soul Surfer on 06/05/2007 19:33:33

The upside down siphon is just like a u tube  the water will rise to the same level on the other side of the vally provided the  pipe will stand the pressure at the bottom of the valley without leaking or exploding.  The pressure at the bottom is around one atmosphere for every ten metres below the starting level it goes.  the level at the far side will need to be a bit lower on the output side to create a bit of pressure differential to get a good flow of water.

Title: Inverted syphon of the roman aqueducts
Post by: Aira1990 on 06/05/2007 22:59:38

thanks so much!!!!! ok so the deeper the valley, how far down the pipe goes, the stonger the pipe has to be to withstand presure right

Title: Inverted syphon of the roman aqueducts
Post by: Batroost on 06/05/2007 23:22:38

Yep. And I've seen this in England. There is a small stream that passes under a canal in Somerset in just this manner.

Title: Inverted syphon of the roman aqueducts
Post by: Aira1990 on 07/05/2007 01:40:11

haha thats trippy!! you guys are such great help  [;D] thanks so much!!

Title: Inverted syphon of the roman aqueducts
Post by: daveshorts on 07/05/2007 11:05:46

I would doubt that the romans did this for very steep valleys, because although it would work fine, the pressure at the bottom would be such that using the technology of the time it would be almost impossible to stop the pipe leaking if it was deep, apparently they had to split the pipe into lots of small ones to be able to stand the pressure. This is why they still built aquaducts for deep valleys.

Title: Inverted syphon of the roman aqueducts
Post by: Aira1990 on 07/05/2007 11:28:05

would it make sense if they built up the bottom a bit then run the pipe across? it would be easier than building a huge arcade.

Title: Inverted syphon of the roman aqueducts
Post by: daveshorts on 07/05/2007 11:40:31

Yes that would help certainly as the thing which will cause your pipes to explode is the drop from the bottom to the top.

Title: Re: Inverted syphon of the roman aqueducts
Post by: kiminoa on 09/01/2012 04:57:59

This thread inspired a Quora question:
http://www.quora.com/In-the-context-of-the-aqueducts-what-is-a-quinaria-in-Latin

I was reading up on inverted siphons today to make sure I understand what they were and how they were used in Roman water works, and found this thread.  The article[1] I was reading used the Latin word "quinaria" to refer to a "5-finger pipe" which was then interpreted to mean a lead pipe circumference.

When I saw the comment from daveshorts about splitting the pipe to withstand the pressue, I wondered if perhaps quinaria could also be a lot more literal, and refer to a pipe split into 5 "fingers" to increase its surface area.  Thoughts?  I need to bone up on my Latin and confirm what "finger" actually refers to here.  I'm not sure if the word is used synonymously to mean a measurement type and human digit both in Latin.

For anyone who is curious, the quote I was looking at comes from Pliny Nat. 31.58:
in anfractu omni colli(s) quinaria fieri, ubi dometur impetus necessarium est
"At every bend, where it is necessary to control the momentum, colli(s) quinaria must be build."

[1] Nikolic, Milorad 2011 Mnemosyne Ser. IV Vol. LXIV Fasc. 3 "An Investigation of Vitruvius' Technical Vocabulary Relating to Water Conduits and Pipelines in De. arch. 8.6.6-9: vis spiritus and colluviaria (Re)examined"

Title: Re: Inverted syphon of the roman aqueducts
Post by: CliffordK on 09/01/2012 06:03:51

Unfortunately I was not a Latin student.
I know that in Italian, they use the term "Thumb" for "Inch", but it was never clear if it referred  to the inches/feet that we still use in the USA.

Keep in mind that Five - 1" pipes are much smaller than One - 5" pipe.

I'm surprised that one couldn't design lead lined stone to take the pressure of a hundred foot drop or so.  I'd hate to be the person climbing inside to seal the lead, and one would still need some kind of drain valve at the bottom for conducting repairs.

Maintenance on a low pressure system would be much easier.

An "inverted siphon" as discussed might still be used for things like going under roads.

Title: Re: Inverted syphon of the roman aqueducts
Post by: MikeS on 09/01/2012 06:38:26

I understand that the Romans (and many cultures since) have used the same system to find a  level.  If a pipe is made into a long u shape with the ends pointing up, if the pipe is filled with water then it will find a 'level'.  By lifting or dropping the ends of the pipe such that water is level with the end of the pipe then the ends of the pipe are level.

Title: Re: Inverted syphon of the roman aqueducts
Post by: syhprum on 09/01/2012 08:57:59

Siphons do not keep going for long if there is dissolved gas in the water.

Title: Re: Inverted syphon of the roman aqueducts
Post by: Soul Surfer on 09/01/2012 17:52:51

This problem does not occur with inverted siphons although the theoretical limit for normal siphons is 30 ft.

Title: Re: Inverted syphon of the roman aqueducts
Post by: CliffordK on 09/01/2012 20:16:34

Quote from: syhprum on 09/01/2012 08:57:59

Siphons do not keep going for long if there is dissolved gas in the water.

I would suppose that would depend on a number of factors.  How high the siphon is, are you talking about dissolved gas, or bubbles, size of hose, flow, how easy does the gas come out of solution, elevation difference between inlet and outlet, and etc.

There is always some amount dissolved gas in water, but a siphon can be quite effective.  The effective vapor pressure decreases to the maximum height of the siphon (34 feet for water).  Nonetheless, to a large extent, the siphon will pull bubbles through the line, even if they do happen to form.

However, what is described here isn't a true siphon, but rather a connected tube of a water column, so technically it could be of unlimited height, and vapor is not an issue.

Title: Re: Inverted syphon of the roman aqueducts
Post by: yor_on on 12/01/2012 10:11:39

Another interesting thing that I saw in a program. Those old aqueducts for waste used to have 'U' forms, well not really like this, but some similar small constructions following the walls at certain distances creating 'backflows' as i understands it, cleaning the aqueducts from debris. Very clever.. I don't think we have anything similar, but they had it ?_000 years ago :) in Egypt. Cleopatra as a guess? Romantic times that

As a vague memory, and no.
I'm not that old.