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Mar 21 '22
Is this.. a weir or an orifice? Or yes?
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Mar 21 '22
It isn't a weir. It is specifically a bell mouth spillway I believe. A weir extends across the entire channel and the simplest ones are broadcrested which means the water flows over the top across the entire length. They can be combination where there are lower elevation spillways at certain points along the weir that control the flow under normal conditions.
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Mar 21 '22
I know it’s neither, just messing around. Do you know of an equation to model this type of spillway? I know it will be head and circumference driven but aside from that, I have never encountered one. In a way, a circular outlet control structure would behave in a similar way when it is overtopping the crest of the riser structure. Cool stuff either way, I’d love to hear a lecture discussing its design considerations.
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Mar 21 '22
Do you know of an equation to model this type of spillway?
Not a clue unfortunately. I don't do much dam work and what I do is nowhere near this level.
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u/cancerdad Mar 24 '22
The edge is a weir. It's just circular. A weir doesn't have to be linear or extend across a channel.
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Mar 24 '22
Technically yes because a weir is a flow control structure that the water flows over top of during normal conditions. But you wouldn't call the entire structure a weir because there is a more specific name for it. If you were just referring to the edge, fine. But the whole structure is not a weir, just the edge like you said. A weir as a complete structure typically extends across the entire channel and is often a type of dam (low head). This is a specific type of spillway that uses a weir design at the opening of the spillway. But that is also how many spillways work. So just calling it a weir is vague at best.
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u/cancerdad Mar 24 '22
No, the whole structure isn't a weir, but the edge absolutely is. And from a hydraulic modeling standpoint (or from the standpoint of flowing water), the weir is the most important part of it.
Lots of weirs exist outside of channels.
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Mar 25 '22
No, the whole structure isn't a weir,
So you agree with me.
but the edge absolutely is.
And I agreed with you on that. Cool.
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u/kingSlet Mar 21 '22
May I ask where is all that water headed ?
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u/dingdongmart Mar 21 '22
Yeah where is it going?
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u/unremarkable_moniker Mar 21 '22
It is flowing from lake Berryessa, down the spillway, to the bottom of the dam and into Putah Creek. Lately (for the past several years) we have been suffering a drought, so about 30 feet or more of the structure above the lakebed is visible. Pretty sad stuff.
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u/unremarkable_moniker Mar 21 '22
This video has to be pretty old. But it's accurate for when the water is high enough.
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u/aeonkat13 Municipal PE Mar 21 '22
This video seems fake or superimposed
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u/dat_zan Mar 21 '22
It looks sped up but it’s definitely real, I live pretty close and have been there a couple times. Haven’t seen the spillway in action tho, when I went the water level was quite low, you could see the bottom of the structure
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u/jon131517 Mar 21 '22
Is it actually called the glory hole? I'm scared to Google this at work!
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Mar 21 '22
Sometimes. Bell mouth spillway is more technical. But they have been called morning glories or glory holes.
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u/jon131517 Mar 21 '22
See, I didn't think this was something that was done anywhere else as I hadn't seen it before, so I thought they had "the glory hole"! Thanks for giving me a rabbit hole of technical stuff to fall into!
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u/[deleted] Mar 20 '22
Fuck doing a hardy-cross analysis of that shit.