I am not an expert in Physics, so please go easy on me. The magnus effect creates a perpendicular force to the axis an object spins around and the velocity vector. But where does that energy come from? Does the object loose energy by slowing down the spin or the velocity? Every object that experiences the magnus effect looses velocity through friction, but does it loose considerably more energy than without spin (assumed the object is a sphere or a cylinder)?
Answer
The Magnus effect , which applies to objects which have circular symmetry about the axis of spin, stems from the fact that the side of the object spinning towards the air flow (from forward motion) sees a higher air speed than the side spinning away from the direction of air flow. The thin layer of well-behaved (jargon: laminar) air becomes turbulent earlier on the faster side (jargon: it has a higher Reynolds number). Therefore, the turbulent wake behind the object is lopsided. This asymmetry leads to a tangential force. This phenomenon is not easily thought of in terms of energy. Yes, the object slows down and spins more slowly from drag but these only affect the forward speed and amount of tangential force respectively. I would guess that, yes, comparing objects with the same amount of kinetic energy to start but one has only translation kinetic energy while the other has translation AND rotation kinetic energy, the one with rotation will transfer more energy to the surrounding fluid.
No comments:
Post a Comment