Abstract
We present one estimation method of the aerodynamic coefficients and the axis of rotation of a ball in flight from the trajectory data of the ball. In this method, local geometrical quantities of a spatial curve obtained from the trajectory are related to fluid forces included in the motion equation of the ball. The purpose of the present study is to clarify the unsteady aerodynamic forces acting on the ball via the analysis of the flight trajectory-based estimation method. In order to confirm the accuracy of the estimation, sample trajectory is used, which is simulated by giving the aerodynamic coefficients and the rotation axis. The estimated results are in sufficient agreement with the given conditions. Also, the present method reproduces the aerodynamic coefficients and the axis of rotation from three-dimensional trajectory measured with golf ball. In this estimation, the accuracy is improved by using the interpolation of velocity data, and the results show smooth variation in the aerodynamic quantities. In particular, it is found that the acceleration and/or deceleration in the ball motion affects drag more significantly than the Magnus force. Moreover, we estimate the aerodynamic coefficients from two-dimensional trajectory data of three types of golf ball with different specification. The results clarify the effect of the specification to the aerodynamic coefficients, and this fact support the validity of the present estimation method.
