Water flow in a lake...
Water flow in a lake...
(OP)
New engineer here. This is what happens when the fish are not bitting. If a dam gate is open and water starts flowing thru the dam, how long does it take for a boat 10 miles away to start floating towards the dam? For numbers, let's say the gate is 20ft X 20ft and is 60ft below the water level. The lake is 30ft deep and is 600 feet across. I can calculate the flow thru the gate and the volumme of water in the lake to the boat and divide, but I don't think this is how to work this problem. Any formulas and help is appreciated.
Hoot60
Hoot60





RE: Water flow in a lake...
RE: Water flow in a lake...
RE: Water flow in a lake...
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RE: Water flow in a lake...
Actually sounds like a "how long is the string" question to me.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Water flow in a lake...
Recalled from an Electrical Engineer's Handbook dating to about 1900, which included details about designing hydro dams:
If the gate opening is in a horizontal plane, such that the flow is generally downward, fish will be drawn into the gate and discharged through the spillway.
If the gate opening is in a vertical plane, such that the flow is generally horizontal, and the flow velocity does not exceed their speed capability, the fish will swim away from the gate and not be sucked into it.
Fish are extraordinarily sensitive to lateral pressure, demonstrated by near simultaneous turns of entire schools. They are much less sensitive to up/down pressure, so will be sucked into a vertical flow, as in a simple drain.
This is why the racks at hydro volute entrances are called 'trash racks' and not 'fish racks'.
</tangent>
Mike Halloran
Pembroke Pines, FL, USA
RE: Water flow in a lake...
RE: Water flow in a lake...
BTW how is the gate 60ft below the water level when the lake is only 30 ft deep?? Is it horizontal gate or vertical gate? It will make a difference. What is your flow rate? You can only calculate this if you know what is on the other side of the gate. Too many unknown variables! How long is the lake?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Water flow in a lake...
And if the boat is in the center of the channel, current will be quite a bit faster (30% more than average, or so) than if drifting along the edges.
RE: Water flow in a lake...
Besides, being such a nonsense question, it's an odds on bet it's student homework.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Water flow in a lake...
Just answering the question as asked.
RE: Water flow in a lake...
RE: Water flow in a lake...
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RE: Water flow in a lake...
wind is going to have to be discounted as this will have more effect than anything else.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Water flow in a lake...
RE: Water flow in a lake...
RE: Water flow in a lake...
Suspect the "boat grounds on bottom of lake" is correct answer if lake is long and has a shallow contour of the original bottom. Been across that lake, but not on it.
RE: Water flow in a lake...
RE: Water flow in a lake...
RE: Water flow in a lake...
RE: Water flow in a lake...
If you evaluate it according to Chow's method, the velocity through the 30 feet deep channel will be moving at square root of g*y or 31 ft/sec. At 10 miles of distance, the velocity of flow will pass the boat in 28 minutes. You will not feel it passing.
The dam break analysis is shown in example 19-5.