inverted siphon

[Anonymous]

Hi.

Anyone know how to model an inverted siphon? I have been reading and some say that may be used “lids” in sections, however when I view the results, don’t see that the water depth is limited to the defined section.

I also thought that adding three culvert segments might work but I can’t put a distance “0” of the upstream section, so I can’t connect the culverts.

Thank you

[Anonymous]

If you are trying to model a culvert with a lid (and you don’t want any weir/overtopping flow) make the top of the deck higher than the maximum energy grade. If the cross section with lid is fully pressurized, RAS will display a water surface above the top of the cross section/culvert, but all of the flow should be contained inside of the cross section. (If the water surface is above the top of the deck, make the top of the deck higher.)
The displayed water surface is actually the “hydraulic grade line”.

[odigirbjohn]

Hello Jarvus I appreciate you taking the time to respond

As I wrote previously I used the “lids” option but the results do not seem appropriate, because the line of water surface is very similar to that shown me before using this option. Then when I view the profile it doesn’t show me the actual dimensions of the “lids”.

I’ll show the pictures below

The other option I tried to use was to connect 3 culvert sections, although it is impossible that the connection is tight I think it shows a more adequate result about the behavior of water at the siphon inlet.

Either way I will continue investigating the reason for the results in the option of “lids”

Thank you so much

[Anonymous]

Did you find the solution to model the siphon? I have a similar problem.

[Anonymous]

Has anyone here ever read about “Piessman Slots”

Search it in the manual and you should get a little further on this and find your answer.

[Anonymous]

Hello. I have used the option of priessmann slots in the lids and ran this with unsteady flow but I have gotten a similar problem in the elevation of the water like the first picture of the user odigirbjohn.

[Anonymous]

The next test would to be adding a levee at each bank of the cross section and run it again. If not try a block obstruction. both should do the same thing. You should see a change in the WSEL (rise) unless that was purely a graphical error

[Author]

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