Rotating cylindrical wings? How do they work?
The Magnus effect is an interesting concept that has intrigued aerospace engineers since the dawn of the airplane. To make the most obvious statement of the century, air is quite important when it comes to learning about aerodynamics. Yep, that’s an incredibly blatant fact, but what we might sometimes forget is that air is a fluid that flows and roles around objects in all sorts of weird and wonderful ways. So how can the potential of this particular effect, the Magnus force, be harnessed to make a plane fly?
To understand the Magnus force (or Magnus effect), let’s step back in time for a moment. In 1672, after observing tennis players in a Cambridge college, Isaac Newton correctly identified and described the force that made the tennis balls take a curved trajectory when spun. This was many years before the effect's namesake, German physicist Gustav Magnus, developed a full theory through his studies in 1852.
The knowledge of the force at this time was helpful for military applications as ballistics experts understood what made projectiles, such as artillery shells, follow various trajectories when spun. Later the idea was used to make a cylindrical bomb bounce when spun in the Dambuster raids in 1943. You can read all about this here.
How it works
As a super simple explanation, without getting into the nitty-gritty of boundary layers, flow separation and all of that, we can imagine the Magnus effect in terms of Bernoulli's Therum and Newton's Third Law. With a ball spinning through the air, the rotating ball drags some of the air around with it. Viewed from the position of the ball, the air is rushing by on all sides.
"The drag of the side of the ball turning into the air (into the direction the ball is traveling) slows the airflow, whereas on the other side the drag increases the airflow speed. Greater pressure on the side where the airflow is slowed down forces the ball in the direction of the low-pressure region on the opposite side, where a relative increase in airflow occurs." - Britannica.com
So, airflow in the wake of the ball is deflected downwards through this relative speeding and slowing of the air. Due to Newton's law, an equal an opposite force is applied to the ball meaning that it has lift and travels upwards. This is how a rotating cylindrical wing on a plane could theoretically sustain flight just like a conventional wing.
Use in aircraft
As mentioned previously, the idea of using the Magnus effect to lift an aircraft isn’t exactly a new concept. This plane was the earliest attempt to use a Magnus effect for a heavier-than-air aircraft. It was tested in 1930 with less than promising results. You can read more about this experiment here.
Our friend Peter Sriprol shows you can make a radio-controlled model of a Magnus effect plane with as little as some electronics, two large KFC buckets and a little ingenuity.
Check out this amazing aircraft designed by one of our members on Flitetest.com. This is a radically different take on the Magnus effect airplane and it seems to work! You can check out the entire video right here.
Why not try doing your own Magnus effect plane experiments? Make sure to share them here on Flitetest.com!
Article by James Whomsley
Editor of FliteTest.com
YouTube Channel: www.youtube.com/projectairaviation