スキージャンプの踏み切り直後の動作

Abstract

This paper presents a model of ski jumping movement after the take-off phase. The flight distance of ski jumping is dependent on the aerodynamic forces. We measure the aerodynamic forces using a scale model of a ski jumper for three flight styles (Normal Style, V Style, Flat V Style) and in addition measure the aerodynamic forces present after the take-off motion. The longest flight distance is achieved with Flat V Style. Considering style transition, we calculate the optimal Changing Time (CT) from Normal Style to V Style or Flat V Style to V Style with computer flight simulation. The relation between the initial angular velocity of a rigid body model of a ski jumper on the sagittal plane and flight distance is clearly explained. In the take-off phase a significant fraction of jumpers initiate upward motion by rotating the upper body. But others complete this movement with small rotation of the upper body to decrease drag. We performe computer simulations for these two cases from takeoff to 0.4sec after take-off. Linear velocity is greatly decreased with the first jumping technique. The second technique however does not suffer from this velocity decrease.