Effects of Wind on the Aerodynamic Characteristics during Flight in Ski Jumping

Objective:To determine the effects of wind on the aerodynamic characteristics during flight in ski jumping. Methods:Numerical simulation of computational fluid dynamics(CFD) was used to predict the aerodynamic characteristics during flight under different environmental wind, and the effects of horizontal wind, vertical wind and lateral wind on the aerodynamic characteristics were investigated as well. The athlete and skis were regarded as a multi-body system, and partially averaged NavierStokes(PANS) turbulence model was used to simulate aerodynamic characteristics of the system based on a general flight attitude,and then the forces, torques and flow field form data were obtained. The horizontal wind speed includes-4 m/s,-2.5 m/s,-1 m/s,0 m/s, 1 m/s, 2.5 m/s and 4 m/s, the vertical wind speed includes-8 m/s,-4 m/s,-2.5 m/s,-1 m/s, 0 m/s, 1 m/s, 2.5 m/s, 4 m/s and8 m/s, and the lateral wind speed involved includes 1.5 m/, 3.0 m/s, 4.5 m/s, 7.5 m/s, 10.5 m/s and 13.5 m/s. Results:1) The lift,drag and pitch torque of the multi-body system under horizontal wind were changed significantly, and the correlations of lift, drag and pitch torque with wind speed were approximately linear. At the same time, the growth rate of mechanical properties under horizontal upwind was higher than that of mechanical properties under horizontal downwind. 2) When vertical wind speed was less than 2.5 m/s, the lift, drag and pitch torque increase slowly, but when vertical wind speed was greater than 4 m/s, they began to increase relatively rapidly. In addition, vertical upward wind caused the lift, drag and pitch torque to increase, and vertical downward wind caused them to decrease. Moreover, increase rate was obviously smaller than decrease rate. 3) Lateral wind produced yaw force, yaw torque and rolling torque, and had an impact on the lift, drag and pitch torque of the athletes. When the wind speed was less than 3 m/s, these forces and torques were very small, and when the wind speed was larger than 4.5 m/s, they were more obvious.Conclusion:1) The influence of horizontal wind on the aerodynamic characteristics during flight in ski jumping is very significant.In contrast, vertical wind and lateral wind have much less influence, but the influence of lateral wind is more complicated, which causes yaw force, yaw torque and rolling torque obviously to the multi-body system. 2) The influence mechanism of wind on the aerodynamic characteristics during flight in ski jumping can provide effective auxiliary support for on-the-spot prediction and decision-making, and also provide scientific guidance for flight stability control and technical training for athletes.