CFD Analysis of the Magnus Effect | Step-by-Step Tutorial
After the final of UEFA European Championship 2016 yesterday, we decided to celebrate it in our own special way: explaining a scientific phenomenon often occurring in football.
Do you remember a moment when a football player gracefully curved a ball into the goal? Why does this happen?
What is the Magnus Effect?
Well, this is the Magnus effect, the commonly observed effect in which a spinning object moving through a fluid departs from its straight path. This is due to pressure differences that develop in the fluid as a result of velocity changes induced by the spinning body. Important in many ball sports – football included -, the phenomenon affects spinning missiles, and has some engineering uses – in the design of rotor ships and Flettner aeroplanes, for example.
Named after Gustav Magnus, the German physicist who experimentally investigated it in 1853, the Magnus effect is the phenomenon of the generation of a side-wise force on a spinning spherical solid in a fluid.
In ball games, topspin is defined as spin about an axis perpendicular to the direction of travel, where the top surface of the ball is moving forward with the spin. Under the Magnus effect, topspin produces a downward swerve of a moving ball, greater than would be produced by gravity alone, and backspin has the opposite effect. Likewise side-spin causes swerve to either side as seen during some baseball pitches. 
The Magnus effect is a particular manifestation of Bernoulli’s theorem: fluid pressure decreases at points where the speed of the fluid increases. In the case of a ball spinning through the air, the turning 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) retards the airflow, whereas on the other side the drag speeds up the airflow. 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. 
We are not the first ones who investigated this interesting phenomenon. Actually, in this video below from Veritasium, Derek Muller explains it with a real experiment:
Tutorial: Numerical Simulation of the Magnus Effect
This time we thought it might be interesting to teach them how to simulate the Magnus effect. So, are you up for the challenge?
If the answer is yes, here are the steps to a successful simulation:
Step 1: Import the Magnus effect simulation template from the SimScale Public Projects by clicking on this link (you might need to log in).
Step 2: Follow the step-by-step tutorial available on our CAE forum.
Simulation ready? Now let’s visualize the results:
Step 3: Post-processing tutorial
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