6
votes
Accepted
How and WHY does the tension in an arch dam or bridge change as the degree of curvature and radius of curvature change?
The presence of tension in an arch is not really dependent on the curvature but on how well the arch matches a catenary shape.
Robert Hooke famously stated:
As hangs a flexible cable so, inverted, ...
- 2,651
6
votes
Instead of dams to tap hydroelectric power, why not just pipe the river from further upstream, and then let the water fall down a great height?
This is in fact quite common. It's called a diversion hydro facility as opposed to an impoundment (dam) facility or pumped storage facility.
- 5,105
4
votes
Why don't hydroelectric plants use cascades of turbines instead of single turbines?
The reason why a hydroelectric generator is fundamentally different to a gas turbine is because water under pressure is not a gas, and does not change size significantly as energy is extracted from it....
- 41
3
votes
Why did they move ancient Egyptian temples to prevent them from water damage instead of encircling them with a dam?
Shielding them by a dam would have been more costly. And being hidden under a 65 meters deep wall into the water of the Aswan dam would make them visually disappear, and lose their glory.
As it is now ...
- 22.8k
3
votes
Can the kinetic energy formula (1/2 m v²) be used in finding amount of energy a hydro electric station can produce?
No its not accurate.
In the case you are describing the 20 kg of water have 1000 joules of energy.
If you had a mass rate of 20 kg/s and the fluid was moving at 10 m/s then you could have claimed that ...
- 24.3k
3
votes
Why do dams deplete rivers?
The answer has nothing to do with Bernoulli's equation.
A large dam across a steep canyon will define a large catchment volume. It is not uncommon for such a catchment to take as long as ten years to ...
- 15.3k
2
votes
Why do dams deplete rivers?
Some dams are designed to even out the natural river flow so that the level or height of the river is relatively constant.
The natural change in rainfall over time causes a natural change in river ...
- 16k
2
votes
Does a spillway failure have different consequences versus dam failure?
If a dam collapses catastrophically, the entire volume of the lake is released in one 'pulse.' This means the downstream area will be subjected not only to a wave of great height but also of great ...
- 4,259
2
votes
Does a spillway failure have different consequences versus dam failure?
Spillways are designed to control the water flow (and excess waterflow) past a dam.
Spillway failure could mean a variety of things, but the primary difference is that the spillway is most always ...
- 8,285
2
votes
Different equations for Hydropower
Unless the second version has Q in litres per second ie kg per second, which is a version hydraulic engineers use.
They will also use g as 10 instead of 9.81, because it is "close enough" ...
- 16k
2
votes
Can the kinetic energy formula (1/2 m v²) be used in finding amount of energy a hydro electric station can produce?
This idea works reasonably well for an impulse turbine (e.g. a Pelton wheel) but it doesn't work at all for a reaction turbine (i.e. something with blades which the water flows through).
The reason is ...
- 12.6k
2
votes
Why do dams deplete rivers?
I suggest that this is not an engineering problem, but a political one. Yes, dams reduce flow downstream when they are filling up, but this isn't a long-term issue. The issue is that once a dam is ...
- 7,148
2
votes
Instead of dams to tap hydroelectric power, why not just pipe the river from further upstream, and then let the water fall down a great height?
You need to remember that the daily electricity demand is not constant or deterministic (you don't know it exactly in advance). Generally through the day has fluctuation similar to the following:
**...
- 24.3k
1
vote
Different equations for Hydropower
The second equation is wrong, while the result is correct. This just happens to work, as the density of water can be assumed to be $\rho=1'000kg/m^3$. So basically, the numerical result you get from ...
- 1,186
1
vote
Accepted
How can a masonry dam not require mortar?
A "face" coating that provides the waterproof layer.
There are many materials used, from polymers to asphalt, cement etc
The material is chosen as it has to resit water movement - driven by ...
- 16k
1
vote
Where are the energy losses here?
Siphons don't work uphill.
Any system that claims to be self-sustaining is not only wrong, but is prima facie wrong. All you have to do is figure out where.
- 7,148
1
vote
Pumped storage hydropower, how to power the pumps?
Yes, electrically.
The normal purpose of these systems is to provide peak power generation capacity. Peak power often has to be generated via expensive fossil fuel systems. Peak power demand is ...
- 7,148
1
vote
Does the volume of water going through a hydroelectric dam matter?
Hydraulic power is the product of a flow variable (mass per second) times the effort variable (pressure head). To increase the output power of a hydro plant, the flow is increased by opening up the ...
- 15.3k
1
vote
Does the volume of water going through a hydroelectric dam matter?
The Efficiency of a turbine is expressed in a Hill Chart -
The efficiency can be improved at off-design points by using variable geometry guide vanes in the induction section, as described in the ...
- 5,105
1
vote
Can the kinetic energy formula (1/2 m v²) be used in finding amount of energy a hydro electric station can produce?
Usually a first approximation is based on Q * g * h,
Q flow in l/s
g gravity - assumed to be 10 since efficiency will cover difference between 10 and 9.81...
h is height in metres.
- 16k
1
vote
Calculating Flow rate and Water Velocity of a pipeline
This question cannot be answered as it is (without numerical values). The main reason is that you need to determine the pressure Losses due to the pipe length. However the pressure losses are ...
- 24.3k
1
vote
Calculating flow rate from a given water tank and water head in hydropower
Let's assume a given water volume of 100 cubic meters a day and a water head of 100 meter.
100 m3 = 100 T = 100,000 kg. That's a lot of weight and a lot of valuable space in a high rise building.
...
- 11.1k
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