The Aerodynamics of a Diabolo

Diabolo is a popular game in which the object can be spun at speeds of up to 5000 rpm. This high spin velocity gives the diabolo the necessary angular momentum to remain stable. The shape of the diabolo generates an interesting airflow pattern. The viscous air applies a resistive torque on the fast-spinning diabolo. Through computational fluid dynamics (CFD) simulations it’s shown that the resistive torque has an interesting dependence on the angular speed of the diabolo. Further, the geometric shape of the diabolo affects the dependence of torque on angular speed.