Originally Posted by
Vessbot
The opposite would happen if an inward-shooting bolt cannon at the blade tip, shoots a bolt initially toward the hub. An observer at the cannon would see the bolt curve forward and to the right, while an outside observer would see it go in a straight line (yet still forward of the blade). This is Coriolis force, and it is a direct result of the conservation of angular momentum. They're not two different things. Check out this video, skip to the 7 minute mark:
The difference between the free particle that is our inward-shot bolt (or a water droplet in the experiment in the video, or an air parcel on a large scale wind on a rotating planet) vs. a piece of rotor blade in the middle of coning in, is that it's not free but rather rigidly mounted to the rest of the blade. So it pulls the blade forward and RPM goes up.
How does this "apparent" deviation result in an actual force/torque? Seems like a something-for-nothing deal, which we know isn't possible. From an energy budget perspective, we know that angular momentum was conserved: for a free particle, decreased radius converts to a higher angular speed. This can also be put in terms of straight-ahead plain old momentum: Actual speed stays the same, which means that the distance per time stays the same. Which means that the same distance (per time) wrapped around a smaller circle, covers more angle (per time). So the "apparent" path deviation to the right (to an observer rotating to the left with the system) is still a very real angular speed deviation, pulling the rotor forward.
Vessbot Thanks for your input. The video is a great representation of the Coriolis effect, however, it really doesn't focus on the law in question; conservation of angular momentum.
Coriolis Effect and conservation of angular momentum are absolutely different! Stating that Coriolis effect is the same as conservation of angular momentum is like saying distance is the same as speed in the old speed, distance, time formula.
It is important to remember that two different physical principles are involved when defining Coriolis 'force', namely, conservation of absolute angular momentum and centrifugal accelerations felt in the rotating frame.
Coriolis effect is reserved for describing the fictitious deflection of a moving object in an a non-inertial rotating frame of reference. It is nothing more than a method to quantify the magnitude of the fictitious force. However, in the case of a rotor system there is nothing 'fictitious' about a rotor rpm speed change, it is actually happening. This phenomena is the direct result of conservation of angular momentum. The formula that defines the rpm change:L=R x MV
where R =radius, m =Mass, V = linear velocity
So, with or without the genius Mr. Coriolis' calculation of the apparent deviation, the blade rpm change is going to happen. Why not call it what it actually is?