Centrifugal overunity - An imaginary experiment

[vineet_kiran]

 
Just a thought experiment

[Low-Q]

If directions of nozzles and directions of non-return valves provided inside the nozzles are so adjusted that the momentum of air moving in and out of the tube always helps the tube to rotate further in its direction of rotation insead of opposing it, will not the rotation become
perpetual?

The answer is no.


Vidar.

[vineet_kiran]

The answer is no.


Vidar.

Can you explain why?

[Low-Q]

The air flow and its trust will correspond to the centrifugal force given by the pistons. The pistons cannot provide more energy out of the nozzles than the energy required to accelerate the mass in the pistons.


I have explained an experiment at physicsforums.com here. You can read this and maybe understand the relationship between trust and airflow in a very simple centrifugal pump I made a while ago.
http://www.physicsforums.com/showthread.php?t=542102


Look at post 7 for reference. The "piston" in the experiment is just air.


Vidar

[Low-Q]

In the experiment above I used water, not air. Sorry for the confusion.


Now, I did a simulation in PHUN (Not a very advanced software, but it use general physics as "platform"). I made a tube with a 90 degree bend at the end. Then I put a heavy ball inside it, close to the hub, and pushed it into rotation. The initial rpm was 4. As the heavy ball moves outwards due to centrifugal forces, the rpm slows down as expected. When the ball hits the bend, the tube accelerates till 4 rpm again, and the ball stop moving.
This operation can therfor compare with an electric car which use energy to accelerate, and where the motor generates the same energy back to the battery as it slows down to a full stop.


This means that the ball has gained kinetic energy from both centrifugal force and coriolis force, and release all that energy back to the tube at the exit.


It does not matter how heavy the tube is. The difference is, as heavier the tube is, the less the tube slows down during operation while the ball is still inside on its way out of the tube.


Now you think that it is possible to take out some of the kinetic energy from the ball. That is possible, but not on expence of the final angular momentum of the tube. So energy must be added in order to sustain angular momentum. My guess is that the loss by friction is the same as the neccessary energy supply to sustain angular momentum in the tube after the ball has been released.


I will try to post a crappy video of the scenario later today on youtube.


Vidar