Bernoulli to explain Magnus Effect

• JTC
In summary, the conversation discusses the cause of the Magnus effect and how it is often mistakenly attributed to Bernoulli's equation. The effect is actually caused by circulation and is not explained by Bernoulli's principle. The conversation also mentions that the Wikipedia article on the Magnus effect does not mention Bernoulli, but instead explains it using Newton's Third Law and air friction.

JTC

Hi

I have been reading some internet articles that state the Bernoulli equation does NOT explain the Magnus Effect. The articles state that the effect is due to circulation (Bernoulli requires inviscid flows)

Could someone explain the cause of the Magnus effect without reference Bernoulli's equation?

In other words, I pieced this together from reading... If this is true, could someone elaborate and then explain the cause of the effect?Many attribute the effect to Bernoulli’s equation wherein fast moving fluid. However, Bernoulli’s principle doesn’t cause anything. It is a calculation scheme. It let's one calculate the pressure when you know the velocity. It has restrictions in its use. It is only valid along a streamline. It is only valid for inviscid flow (fluid with zero viscosity). It is only valid for incompressible flow (constant density fluid).The Bernoulli argument is somehow flawed because the velocity difference does not lead to pressure difference, it is the circulation that leads to pressure difference. Bernoulli principle always assumes no viscosity and vorticity.

Last edited:
kuruman said:
Did you see this wikipedia article?
https://en.wikipedia.org/wiki/Magnus_effect
There is no mention of Bernoulli, just Newton's Third law which gives an intuitive explanation in terms of air friction.
Normally, I check wiki. this time, I did not. Thank you!

1. How does Bernoulli's principle explain the Magnus effect?

Bernoulli's principle states that as the speed of a fluid increases, its pressure decreases. This principle can be used to explain the Magnus effect, as it describes the relationship between air speed and pressure around a spinning object. When an object, such as a spinning ball, moves through the air, it creates an area of low pressure on one side and an area of high pressure on the other. This pressure difference creates a force, known as the Magnus force, that causes the object to curve.

2. What is the relationship between spin and the Magnus effect?

The Magnus effect is directly related to the spin of an object. As an object spins, it creates a difference in air pressure on either side, which leads to a force that causes the object to curve. The more spin an object has, the greater the Magnus force will be, resulting in a more dramatic curve.

3. Can the Magnus effect be observed in other situations besides sports?

Yes, the Magnus effect can be observed in various situations besides sports. It is commonly seen in aviation, such as in the design of helicopter rotors, and in marine propulsion systems. It is also utilized in wind turbines and some engineering applications.

4. How does the shape of an object affect the Magnus effect?

The shape of an object can influence the Magnus effect. Objects with a smooth, streamlined shape tend to experience less air resistance and therefore, produce a weaker Magnus force. On the other hand, objects with an irregular or rough surface can create more turbulence and result in a stronger Magnus force.

5. Is the Magnus effect always beneficial?

The Magnus effect can be both beneficial and detrimental, depending on the situation. In sports, it can be used to curve a ball in a desired direction, making it more difficult for opponents to catch or hit. However, in some engineering applications, such as wind turbines, the Magnus effect can cause unwanted vibrations and instability. Therefore, it is important to understand and control the Magnus effect in different situations.