# Reverse Magnus Effect: Exploring Lift Force & RPM Relationship

• robhlee
In summary: This means that the NASA guy was not mistaken in his statement, as the relationship between rpm and lift force remains linear, but the effect of a rough surface on the lift force must also be considered. In summary, the maximum/restricted rpms in the FoilSim application are in place to simplify the concept for middle school students, and the reverse Magnus effect is a result of a rough surface on a spinning object, which can negate the expected lift force.
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?

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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.

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.

## 1. What is the Reverse Magnus Effect?

The Reverse Magnus Effect is a phenomenon in which a rotating cylinder or sphere experiences a lift force in the opposite direction of the spin. This effect is opposite to the regular Magnus Effect, where the lift force is in the same direction as the spin.

## 2. How does the Reverse Magnus Effect relate to lift force and RPM?

The Reverse Magnus Effect is directly related to the lift force and RPM (rotations per minute) of the object. As the RPM increases, the lift force also increases. However, there is a point at which the lift force decreases due to the formation of turbulent wake.

## 3. What factors affect the Reverse Magnus Effect?

The Reverse Magnus Effect is affected by several factors, including the shape and size of the rotating object, the fluid density, viscosity, and velocity, and the surface roughness of the object. These factors can impact the formation of the turbulent wake and therefore affect the lift force.

## 4. How is the Reverse Magnus Effect used in real life?

The Reverse Magnus Effect has several practical applications, including in sports such as tennis and golf, where spin is used to generate a lift force on the ball. It is also utilized in some industrial processes, such as mixing and pumping, as well as in some propulsion systems.

## 5. What are some potential areas for further research on the Reverse Magnus Effect?

There are still many unanswered questions about the Reverse Magnus Effect, and further research could be done in areas such as the effects of different fluid properties, the impact of surface roughness, and the behavior of rotating objects in non-uniform flows. Additionally, the practical applications of this effect could also be explored further.

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