## 3 Results
### Aerodynamic Forces and Moments
The variation curves of the mechanical characteristics of the multi-body system under different yaw rotation angles are shown in Figure 5. It can be observed that, influenced by the yaw rotation, the multi-body system exhibits asymmetric flight postures, resulting in a significant yaw force, yaw moment, and roll moment. The yaw force acts along the  
Figure 5: Change curves of aerodynamic characteristics under different yaw rotation angles. (**a**) The changes with different yaw rotation angles in total lift, total drag, total lift-to-drag ratio, pitch moment, yaw force, yaw moment, and roll moment. (**b**) The changes with different yaw rotation angles in athlete’s lift, athlete’s drag, athlete’s pitch moment, athlete’s yaw force, athlete’s yaw moment, and athlete’s yaw force, athlete’s yaw moment, and skis’ roll moment. Figure 6: Change curves of aerodynamic characteristics under different roll rotation angles. (**a**) The changes with different roll rotation angles in total lift, total drag, total lift-to-drag ratio, pitch moment, yaw force, yaw moment, and roll moment. (**b**) The changes with different roll rotation angles in athlete’s lift, athlete’s drag, athlete’s pitch moment, athlete’s yaw force, athlete’s yaw moment, and athlete’s roll moment. positive Z-axis, the yaw moment along the positive Y-axis, and the roll moment along the negative X-axis. The magnitudes of these forces and moments increase monotonically with the yaw rotation angle. Moreover, although the yaw force of the athlete is greater than that of the skis, the magnitudes of the athlete's yaw moment and roll moment are smaller than those of the skis. At a yaw rotation angle of 2.5\({}^{\circ}\), the yaw force, yaw moment, and roll moment of the multi-body system are relatively small, approximately 8.78 N, 2.16 N\(\cdot\)m, and \(-\)1.67 N\(\cdot\)m, respectively. However, when the yaw rotation angle increases to 7.5\({}^{\circ}\), the yaw force is 24.89 N, the yaw moment is 6.78 N\(\cdot\)m, and the roll moment is \(-\)5.26 N\(\cdot\)m. Additionally, the yaw rotation also has a significant impact on the lift, drag, and pitch moment of the multi-body system. The lift of the multi-body system, athlete, and skis decreases monotonically with the yaw rotation angle, while the drag of the multi-body system and ski increases monotonically with the yaw rotation angle. Consequently, the total lift-to-drag ratio of the multi-body system exhibits a monotonically decreasing trend. Furthermore, although the variation in the pitch moment of the multi-body system is relatively insignificant, the pitch moments of the athlete and skis exhibit noticeable changes, with their magnitudes increasing monotonically with the yaw rotation angle. At a yaw rotation angle of 15\({}^{\circ}\), the reduction in total lift of the multi-body system is 10.14 N, the increase in total drag is 36.71 N, the decrease in the total lift-to-drag ratio is 0.439, and the increase in pitch moment is 2.59 N\(\cdot\)m.  
The mechanical characteristics of the multi-body system under different roll rotation angles are shown in Figure 6. It can be observed that the asymmetry of the flight posture of the multi-body system is significantly influenced by the roll rotation, resulting in a noticeable yaw force, yaw moment, and roll moment. Specifically, the yaw force is directed along the negative Z-axis, the yaw moment along the negative Y-axis, and the roll moment along the positive X-axis. The magnitudes of these forces and moments consistently increase with the increase in roll rotation angles, displaying a monotonic upward trend. Furthermore, it is evident that the magnitudes of yaw force, yaw moment, and roll moment exerted on the athlete are all significantly smaller than those exerted on the skis. For instance, when the roll rotation angle is 2.5\({}^{\circ}\), the magnitudes of yaw force, yaw moment, and roll moment experienced by the multi-body system are smaller, measuring \(-\)12.33 N, \(-\)3.63 N\(\cdot\)m, and 2.04 N\(\cdot\)m, respectively.