Aerodynamics of a Curveball in NavierStokes Flow
Joey Huang
It is wellknown that the trajectory of a spinning ball is not a straight line  specially for baseball fans. This is socalled Magnus effect. Many people had computed the motion of the fluid around a moving 2D ball (cylinder) when the ball's constant velocity and spinning speed are specified to verify the Magnus effect. This approach can only give us the pressure and stress tensor around the ball  but we can not really obtain the trajectory of the ball.
In this research, I consider the motion of a ball and the fluid around
it simultaneously. A dynamical system of interaction between a ball and
a viscous flow in twodimensional space is proposed, combining the NavierStokes
equations for the fluid and Newton's 2nd law for the ball. A moving coordinate
method is developed to facilitate numerical simulations. The simulations
clearly demonstrate the interaction: the flow changes the motion of the
ball and the moving ball changes the behavior of the flow.
