Energy used by a propeller/motor underwater
Energy used by a propeller/motor underwater
(OP)
There is an electrically operated propeller combined with a motor in a light housing laying sideways in a pool of water (not conventionally upright as on a boat) - think of a helicopter in the water.
The propeller/motor will be 8 metres diameter by 1 metre depth and will weigh 22 metric tonnes.
I would like to find out how much power (energy) the propeller/motor would use if the only thing it had to do was to raise itself upwards by only 10 metres - I know that when it has risen by 10 metres and the motor stops the unit will sink again – the sinking action is immaterial, it is just the energy used in the lift that I am interested in.
The journey time upwards would be fifteen minutes.
The propeller/motor will be stabilized so that it does not rip itself away from it’s moorings. The propeller/motor will be powered by a self supporting external cable so that will not be part of the equation.
Thank you.
Dendalo.
The propeller/motor will be 8 metres diameter by 1 metre depth and will weigh 22 metric tonnes.
I would like to find out how much power (energy) the propeller/motor would use if the only thing it had to do was to raise itself upwards by only 10 metres - I know that when it has risen by 10 metres and the motor stops the unit will sink again – the sinking action is immaterial, it is just the energy used in the lift that I am interested in.
The journey time upwards would be fifteen minutes.
The propeller/motor will be stabilized so that it does not rip itself away from it’s moorings. The propeller/motor will be powered by a self supporting external cable so that will not be part of the equation.
Thank you.
Dendalo.





RE: Energy used by a propeller/motor underwater
A.
RE: Energy used by a propeller/motor underwater
RE: Energy used by a propeller/motor underwater
Two or three real-world effects to take into account:
Remember to allow for the buoyancy of your thingy.
Remember to allow for the efficiency of your thruster and associated drive/shafting - this is unlikely to be good
Work out whether you need to worry about energy loss due to drag (at under a metre per second, you may not be too bothered by this).
A.
RE: Energy used by a propeller/motor underwater
I cannot be any more informative than that because the use to which this will be put has never been done and my engineering discipline is in another area which is why I am here. It is just a rough idea from a rough outline that I have given. If the outline is too flimsy in detail then I will understand and can only thank you for your time.
RE: Energy used by a propeller/motor underwater
If you ballast properly, you could quickly get to the point where the propeller has to do very little work (or none). As well as making the design simpler, a near-neutrally buoyant device is going to be a lot more energy efficient - and you won't have to bother about how to react the propeller torque. Since you're already committed to substantial moorings, you might consider making the platform half a tonne light and then just winching it down to the pool floor. If thrashing about is a compulsory part of the brief, then this sort of arrangement lets you optimise your whisks for thrashing without having to make them generate lift too.
A.
RE: Energy used by a propeller/motor underwater
RE: Energy used by a propeller/motor underwater
A pure potential energy problem does not require the object to expend energy to stay at a fixed altitude, but your object does, which is more like a helicopter than moving an object vertically with a rope and a motor. You may need to peruse this article to find out if you are operating OGE or IGE.
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RE: Energy used by a propeller/motor underwater
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RE: Energy used by a propeller/motor underwater
D.
RE: Energy used by a propeller/motor underwater
http://auvac.org/uploads/publication_pdf/AUV%20Ver...
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RE: Energy used by a propeller/motor underwater