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- เผยแพร่เมื่อ 31 ธ.ค. 2023
- Weirs look like simple structures, but they are crucial engineering structures in open channel flow. I hope you you benefitted something out of this video. Please support us on Patreon - / lesics . That will make a difference. Regards Sabin Mathew
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I hope you enjoyed the video on weirs. I would be truly grateful if you can support us on www.patreon.com/Lesics .Without your support our educational service won't be sustainable. Cheers Sabin Mathew
Sir, how was the zig-zag wier able to reduce the water level more than that in the planer version?
would u accept one time payment?
@@shyamtripathi2097 Hi, I didn't realise our audience would be so much interested to understand the physics behind the zig-zag weirs. I will definitely explain it in a dedicated video.
@@shyamtripathi2097 it is longer. Same as making river wider. Same as putting wider straight weir.
is this guy Indian?! I'm just curious, he has Indian accent
It's good explanation, but it feels a bit incomplete, because it doesn't explain why the zigzag weirs changes the heights of the stream relative to the straight weirs, given that with both the water falls from the same height.
Exactly, wanted to comment this as well
Increased surface area... Change of shape...
Sorry for skipping the physics part of zig-zag weir. I didn't expect this much curiosity around this topic. We will definitely explain it in a different video.
If you explain the physics the videos won't seem so geared to school children..
there is an increased surface area for the water to flow over.
This channel is awesome for integrating the authentic demonstrations with the english graphics. I have enjoyed seeing the real team show real physics models recently along with the narrator guy.
But what about the erosion on the downstream side, it will increase right?
The increase of velocity on downstream can generate scouring on channel base, thus deepening the base of channel.
First time ever i felt a Lesics video gave partial explanation... You guys are amazing always. Please just explain the imoortnace of zigzag wier also.
At a guess, the Zig-zag increases the 'surface area' of the edge, making it act like the spill-over was significantly larger.
Now im not saying the video is wrong but hear me out.
1. It didnt prevent upstream erosion. Erosion happen we just collected it against the weir. This becomes the longterm risk of these systems and in many cases they cant be removed without extreme risk.
2. Maybe Im just saying what was already said. By installing the weir you changed the shape of the rivers flow point from halfmoon to a flat line. The area available for the water to flow was reduced. Resulting in your high upstream height. The other has a longer surface area, allowing for more flow.
3. I find it interesting that you see this as slowing the velocity of the water upstream from the weir. Of course the overall flow rate of the river is going to slow down if your restrict it. The velocity of the water seems to be a result of the area provided for flow. I noticed you didnt mention that but instead had an observational equation to desribe the effect on the water but didnt describe the math that created the effect.
4. Why didnt we mention the erosion taking place down stream will cut a narrow channel now as a result of the faster flow rate but reduced area of flow?
i think those are very good points. i had similar questions, you answered most of them, thanks. also: wouldn't there be a lot of erosion at the downstream side of the weir directly at the weir due to all the turbulence in the water? thinking about it, i recognized my cities weir has additional openings at the bottom and valves with wich they can regulate how much water is flowing over AND under/through the weir at the same time. why exactly would they build it that complicated? has to have a lot of advantages, doesn't it? i thought maybe more constant flow rates and clearence of the collected sediment at the upstream side of the weir or less erosion in general but those are just guesses.
1. It did slow down the upstream erosion though since the flowrate is slower
@yotonking2831 it is possible it did. One issue you can see and they did touch on this is the video is that the upstream sides water table changes. It could be 0 do to a high sided river bank, but it could be catastrophic like we see when a lake is formed. It's highly dependent on soil types and the nature of the installation.
i think it decrease vertical erosion but lateral erosion increase on upstream side. And in downstream side vice-versa. also it depends on topography and geology of rock.
@yotonking2831 it may have. It depends on the topography and mineral density of the substrate. If it floods, you can see erosion in different areas. If it pools and doesn't flood, it changes the water tables so it could have unforseen effects.
The video really demonstrated the concept of weir in a really simpler and easier manner, I really appreciate your efforts and hardwork, but we were also curious in knowing the physics behind zigzag weirs
Length of the weir is diffrent.
It is because of “volume”. If you take the total “length” of the area that water overflows and multiply by the height of the overflow then you have the volume available. The velocity is how fast the flow rate must pass through that volume. AKA… a larger drain pipe.
Using a zig-zag allows a longer “wall” within the width of the channel. Another alternative is to make a wider channel, but doing things like adding a curve/diagonal wall or waves/zigzags are more practical. The zigzag has other benefits when you consider the force of water applied to it.
It's also helpful to mention falling down a wier is extremely dangerous. One will get trapped in the current and be unable to escape. Therefore weirs are often called "drowning machines".
One thing's very strange about physics though- everything about it that seems so hard to understand becomes a piece of cake after knowing the answer
it's just a good explanation
Isnt everything like that😂
I am glad to know that :)
...you mean like literally anything?
Yeah, because that's so simple Europe has a strong push to build back thousands of weirs.
Weirs aggravate floods wakes arrive faster and more violently downstream. The small city upstream is fine while the large city further downstream where 2 large creeks combine totally gets flooded without any warning time.
The people just die in another legislature.
Weirs are also terrible for the aquatic ecosystem.
European Union removes weirs to increase drinoing water quakity and filtration. To redudce flood risk fron fast channled flows.
They reestabkish natural flooding zones and create artificial rapids for the same flood protection effect.
This concrete pouring promo tells youm like 10% of the complex truth.
As a white warer kayaker I can tell you how boring concrete channeled rivers are compared to natural flows. I'm by no means into biology or ecology, the difference in wildlife is staggering in a river having weirs vs one with natural water flow regulation.
There is very few places were such flood protection is essential and other means woukd not work. That's true for thunderstorm collecting basins or mountain zones where snowdrift piles up. Rare places that have frequent flash flood drainage events. Sites nobidy shouldnlive near the river anyways. Thanks to fertilizers and contraception we can start to move out of such dangerous areas. The need to pour them into concrete is basically gone.
The benefit of a species protecting aquatic and floodzone habitat offsetting agricultural monocultures as wildlife reserves is way higher in priorities today. We have to offset fertilizer use.
W/o natural habitats for bees and insects no food grows at all for humans.
China has taken this experiment far enough that people have to manually fertilize the pollen on every apple tree blossom with a q-tip in some regions where bees are extinct.
The most simple use of poured concrete is usually a terrible idea.
Go ask some real experts first before engaging in such projects.
It's not.that easy.
This channel never gets old! I love your content dude
I hope this channel keeps providing us this great content also in the future.
The animation quality is really cool
just wonderful! Thank you LESICS for such a nice video❤❤
I drive past one of these a few times a month and always wondered why not build a damn? It took me 13 years to finally understand the purpose thanks to this video😅
Perhaps you could include a safety warning because many weirs are unsafe. The unsafe ones create a recirculating hole below the weir that spans from bank to bank so that a caught swimmer can only get out by diving down to the fast moving water. Relatively safe weirs have eddies at both sides such that a caught swimmer or boat can swim left or right to get to either eddy and get out of the water. Of course, not everyone knows to swim to the side but it a least gives you a chance. I don't know if that sawtooth makes things better or worse. If a swimmer gets into the point of that tooth, will the water push them along the tooth and out or keep them securely trapped at that apex? (I assume the former but I don't know for sure.)
Great piece of work there, it highlights the principle of energy conservation in a very intuitive visual way
Is it energy conservation? If the downstream river would be deep, the flow would be slow also, dispite the difference in potential energy.
@@paulfontaine7819 Interesting 🤔. My educated guess is that if the downstream river is deep, then there’s more mass of water so more inertia. Thus the kinetic energy of the water accumulated during the time of free fall (because of potential energy) will be lost to friction (so I guess heat?) with the bigger body of water downstream so the effects won’t be the same as when the water levels below are relatively low.
Thanks Sabin Ji for your service
Pls have a little pateronage for your channel ❤
Thank you for creating great educational content for more than a decade.
Thank you man, i love these videos.
Thank you for the presentation!
You must also discuss the hydraulic jump that happens at the downstream side of the dam when the flow of water stabilizes.
The key thing I got from this is that the zigzag presents a much longer barrier over which the water flows thus reducing the increase in height for more flow. The narrator didn't explain that very well, but the diagrams did.
So why does the zig zag work better???? Wow
@4:30
There is one installed at Hope Mills Lake in Hope Mills, NC. It also has different heights within the Weir to regulate water flow.
6:10
Nothing beats this channel about explaining variable engineering theories so kindly but also true that there are so many fun points like this😂
What's wrong with your username😂
@@iaashu98 Corn is a metaphor of tooth in korea 😄
What do you do with the sediment settlement over time?
Can you elaborate?
You CG it away
@@karantekwani3660 sediment/silt (fine particles of dirt and minerals) builds up in layer's seasonally.
Most modern weirs and dams have openings at the bottom and from time to time they get opened to flush out the settlement. There are impressive videos from China where you see a turd like stream of soil getting flushed out from a dam.
@@FritzSchober so that's what those videos are 😂
So well explained, thank you!
The upstream head was reduced by the zig zag because there was more effective weir width for the water to flow over hence less resistance to the flow.
Nice video. TH-cam needs more this kind of educational content
Thanks for the Video!!!
Erosion is controlled upstream due to the weir but erosion is accentuated due to higher velocity flow downstream!
Great work keep it going , Thanks
Very interesting. Thanks for the upload
These things are so simple yet cool
What is the difference between a weir and a dam? It seems like a new word for and old trick.
The difference between weir and dam:
Weir let water trough the crest, but dam forbid it.
On dam, Water flow through the penstock (or tunnel), mainly for power generator. The height of water on dam is regulated
Dam are use for collecting water to power generator or supply, weir are use for prevent surge of water to downstream. Both are reservoir just structure difference
Such a good explanation with animation and models
I really loved it
As im a student and not earning now but when i do i will surely support
Love from India ❤
The graphic of flow area is incorrect on the upstream side. It is determined by the height of water and the effective length of flow over the weir, not the length of the channel upstream. This is why the zigzag pattern is more effective in resisting changes in upstream water level.
nice animation and narration. i hope you bring more because this is still incomplete.
For global scaled, the retained soil either from weirs or dam will reduce the sediment source at estuary which may cause to the beach erossion
Awesome video thank you!
Awesome educational video as always!
I was waiting for you to explain how the linear surface area is what reduces the flow. If X amount of water needs to cross a certain threshold, all you do is add more linear surface there by reducing the overall amount per area.
Thank you for the educational video!
stunning knowledge about engineering Concepts
Good work Sabin Bro
Fantastic! Thank you!!
Fascinating
Great video 👋😄
Please upload all possible videos related to OCF.
REALLY IMPRESSIVE EXPLANATION! ❤❤
Down stream water velocity should be kept at a limit for safety and natural base structure, so maybe a rcc bypass channel from upstream water a few miles before the weir to downstream water will be needed to keep water speed at downstream
Thanks!
Didn't understand the diff b/w zig-zag weir vs straight weir. The video was great as always👍👍❤
Thank you 😊
Thanks for explanations
the increase of mass of the larger river upstream allows more percolation of water through the surrounding soil ...
simple explanation to zig-zag for those who are wondering: discharge over weir directly increases as the effective length of weir increases the zig-zag path gives the weir a greater effective length for the same river width. and as the discharge from zig-zag length is more than straight length ... the water depth in upstream of river in zig-zag weir dont increase more than straight because it's greater length compensates the required cross section of area for the flow.??
I'm guessing the zigzag weir lowers the upstream level by providing a longer line of interaction between the upper and lower water body than the straight weir. equivalent to widening the channel at the weir, but without the extra costs and land usage.
Surely there must be a point downstream at which the velocity of the water slows back down to what it originally was? Assuming no change in slope of the land of course.
The animation quality is really cool
How is this channel not doing great when it has millions of views within a month?
🎉🎉 Good explanation
Wonderful video
best as always
Man we got some "subject matter experts" in the comment section lol. Great video man. Thanks for teaching me somthing new.
Civil engineering is an interesting field
This may work well but surely has it's limits.For instance if the upper stream area can no longer hold enough water during heavy prolonged rains what goes in must come out meaning amount of water still has to go somewhere hence will not stop flooding.
Great video but you forgot to mention the downsides of the weir, like how the river became unnavigable by ship and impassable by fish and other river animals. Also, the danger of a catastrophe if the weir is damaged.
Verry simble explained thank sir
To be honest I would have definitely thought most of the energy gets dissipated on impact. Maybe the cumumated agitation at the bottom of the weir somewhat pressures on the water but I find it pretty bizarre, it's likely to depend on the ability of the river to evacuate the water. another weir later would cancel any increase in speed. That is very very weird.
Indeed. If the downstream river would be deep, the flow would be slow also, dispite the difference in potential energy.
Zig zag has more length of edge for the water to fall over. is this what make the flow easier thier for less height?
My first thought o. Seeing the zigzag was the base is wider so it can withstand more water pressure with less wall thickness. Like coragated vs flat.
the z is not the only way to do this though. I've personally never seen it, here in Germany basically all the weirs I've seen instead opt to follow the falling curve of the water, so they are straight horizontally but curved vertically instead. It's kind of obvious why this works I guess, you have continuous flow all the way top to bottom without any disruption
Great vid. Nice animations also. Who did it? I am defending my phd in hydropower and cfd simulations now, and I am starting another bachelor for Animation. So I will soon be able to make nice animations.
Nice vedio, thanks
Very good and succinct explanation. I am not particularly interested in the flood control, my concern is the conservation of energy. If the velocity of the upstream is lower than the downstream then it is pertinent to take advantage of such increase in velocity to construct a dam that can deliver adequate electricity in my area that has not seen electricity power since this year through this weir. Very insightful video and thought provoking too.
We have Njaba river in my locality in Imo state of Nigeria that can be used to construct dam through this process to improve electricity generation in my state but no one cares.
I love the handheld mic. It looks like you're interviewing the experiment.
Love it!
Thank you for the great explanation ! Why is the energy conserved, and not turned into heat when the cascade of the weir hits the low level downstream?
amazing
It is the basics of fluid dynamics... This is the logic behind the dams..... I didn't understand why there is lots of viewers are surprised about it.. I believe some where in your child hood we might have done this... Blocking flowing water and see that the height increases on one side of it
Can you tell Which software do you use to produce these animations? Thanks for these awesome videos
I was here for how UFO works darn thumbnail artist
Love from 🇧🇩
Nice concept.
However, you didn't explain that the Labyrinth or zigzag spillway increases the length of the spillway so reduces the head increase clearly. .
Also, what respectable engineer measures 200mm of flow with a 150mm ruler?
This could be greatly improved very easily with a few changes.
The basic information is here, it could be presented better though.
Thanks
This is also related to sri lankan ancient "weva" and "amuna" 😊
Very informational
Только проход для рыб снизу нужно сделать - хороший. И поставить гидротурбины. И сделать проезд через плотину - всех видов транспорта. Тогда можно применять.
Ну, и судам надо сделать проход какой то. Шлюзы или что там.
Great...Bravoo
I have seen many beautiful weir constructions in Europe.
Awesome
The sound effect were similar to the Teams sound, twice I got alerted
The Thumbnail: "Weir?"
My brain: "What?"
Although i never searched for this content, I find it very amusing. How WEIRd.
Another explanation that was omitted is that the sediments gather at the base of the weir but we don't know to what extent. Does it eventually fill up, put too much pressure on the weir itself and does it need to be removed eventually?
👍👌 awesome
If a Water turbine could be attached/ installed it would also be a dependable source of power as well.
Thanks very interesting
I hope u keep the English subtitle cuz I learn too much from them😊
Interesting. Does the height of the weir have an impact on the water level delta?
Yes. As an extreme example, a weir of zero height would have a delta of zero.
6:17 cool guy 😎