Reverse Magnus Effect: Exploring Lift Force & RPM Relationship

[robhlee]

Hi,
I was looking at the NASA website's FoilSim application (google it) and for spinning objects, there is a maximum rpm. I was wondering why there were maximum/restricted rpms, so I emailed a NASA guy with the question. He said that the FoilSim App was for middle school students and that higher rpms would create secondary boundary layers, or something like that, too complicated for middle schoolers. He also said that the rpm-lift force relationship remains linear (higher rpm-higher lift force) at higher rpms than allowed in the FoilSim. So then I read about the 'reverse Magnus effect', and now I need a bit of clarification. How would having a rough surface completely negate the reverse magnus effect (according to http://209.85.165.104/search?q=cache...k&cd=1&gl=us ) , and is the NASA guy mistaken when he told me the rpm-lift force relationship remains linear at increasing rpms?

 

[Valerie Park]

Thanks!</code>The Reverse Magnus effect is a phenomenon in which an object (in this case, a spinning object) produces an opposite lift force than expected when the object's surface is rough. This is because the rough surface causes turbulence on the object's surface, reducing the effectiveness of the lift force produced by the spinning object. The NASA guy was correct in saying that the rpm-lift force relationship remains linear at higher rpms than allowed in the FoilSim application, however, if the surface of the object is rough, then the turbulent flow on the object's surface will reduce or even negate the lift force produced by the object, regardless of the rpm.

 

[sir-pinski]

The reverse Magnus effect, also known as the Magnus effect in reverse, is a phenomenon that occurs when a spinning object experiences a lift force in the opposite direction of its rotation. This effect is often observed in sports such as soccer, tennis, and baseball, where a spinning ball can curve or swerve in unexpected ways due to the reverse Magnus effect.

In the context of lift force and RPM relationship, the reverse Magnus effect can play a role in determining the maximum RPM that an object can achieve before experiencing negative effects. As the NASA guy mentioned, higher RPMs can create secondary boundary layers, which can disrupt the laminar flow and decrease the lift force generated by the spinning object. This is why there are maximum/restricted RPMs in the FoilSim application, as it is designed for middle school students and may not accurately simulate the effects of higher RPMs on lift force.

Regarding the relationship between RPM and lift force, it is generally true that higher RPMs will result in higher lift forces, as long as the object is able to maintain a smooth surface and laminar flow. However, as mentioned before, the reverse Magnus effect can disrupt this relationship at higher RPMs. Additionally, the rough surface mentioned in the source you provided can also disrupt the relationship by creating turbulent flow and reducing the lift force.

In conclusion, while the NASA guy may have oversimplified the relationship between RPM and lift force, he is correct in stating that it remains linear at higher RPMs as long as the object maintains a smooth surface and laminar flow. The reverse Magnus effect and rough surfaces can complicate this relationship and may result in a decrease in lift force at higher RPMs.