## 3 Results  
### Aerodynamic Forces and Moments  
The aerodynamic forces acting on the multi-body system include lift and drag. It is important to note that the majority of these forces do not act at the system's CM, which may result in corresponding moments. Under lateral wind and asymmetric postures, there is a possibility of generating yaw force, which can lead to the generation of corresponding moments. Tables 3-5 present the mechanical characteristics under different unfavorable conditions. Figures 4-6 display the variation curves of the mechanical characteristics with respect to the unfavorable conditions. In the results, all forces are the resultant forces acting on the multi-body system or individually on the athlete or the skis, of the same nature. The moments, on the other hand, refer to the moments relative to the system's CM. The pitch moment has a rotation axis along the Z-axis, the roll moment along the X-axis, and the yaw moment along the Y-axis, with the positive and negative directions of these moments following the right-hand rule. The lift-to-drag ratio is calculated as the ratio of lift to drag. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Yaw Rotation** \\ **Angle (\({}^{\circ}\))** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Total Lift** \\ **(N)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Total Lift-to-Drag** \\ **Ratio** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Pitch Moment** \\ **(N-m)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Yaw Force** \\ **(N)** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Yaw Moment** \\ **(N-m)** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Roll Moment** \\ **(N-m)** \\ \end{tabular} } \\ \hline
0 & 297.60 & 151.04 & 1.970 & \(-\)109.34 & 0.00 & 0.00 & 0.00 \\
2.5 & 297.32 & 153.05 & 1.943 & \(-\)109.44 & 8.78 & 2.16 & \(-\)1.67 \\
5 & 296.47 & 155.87 & 1.902 & \(-\)109.58 & 15.89 & 4.27 & \(-\)3.07 \\
7.5 & 295.05 & 159.97 & 1.844 & \(-\)109.77 & 24.89 & 6.78 & \(-\)5.26 \\
10 & 293.08 & 166.94 & 1.756 & \(-\)110.10 & 34.07 & 10.53 & \(-\)8.34 \\
12.5 & 290.55 & 175.68 & 1.654 & \(-\)110.56 & 45.12 & 15.22 & \(-\)12.26 \\
15 & 287.46 & 187.75 & 1.531 & \(-\)110.93 & 56.30 & 21.63 & \(-\)17.37 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Results of aerodynamic characteristics under different yaw rotation angles. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Parameters** \\ **Condition** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Lateral Wind** \\ **Condition** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Yaw Rotation** \\ **Conditions** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Roll Rotation** \\ **Conditions** \\ \end{tabular} } \\ \hline Flight speed (m/s) & 29 & 29 & 29 \\ Attack angle (\({}^{\circ}\)) & 35 & 35 & 35 \\ Angle between velocity and skis (\({}^{\circ}\)) & 35 & 35 & 35 \\ Skis opening angle (\({}^{\circ}\)) & 28 & 28 & 28 \\ Angle between body and skis (\({}^{\circ}\)) & 16 & 16 & 16 \\ Bending angle of upper body (\({}^{\circ}\)) & 18 & 18 & 18 \\ Lateral wind speed (m/s) & 0/1.5/3.0/4.5/7.5/10.5/13.5 & 0 & 0 \\ Yaw rotation angle (\({}^{\circ}\)) & 0 & 0/2.5/5/7.5/10/12.5/15 & 0 \\ Roll rotation angle (\({}^{\circ}\)) & 0 & 0/2.5/5/7.5/10/12.5/15 \\ \hline \hline \end{tabular} Note: The calculation conditions of lateral wind speed include 0 m/s, 15 m/s, 3.0 m/s, 4.5 m/s, 7.5 m/s, 10.5 m/s, and 13.5 m/s. The calculation conditions of yaw rotation angle include \(0^{\circ}\), \(2.5^{\circ}\), \(5^{\circ}\), \(7.5^{\circ}\), \(10^{\circ}\), \(12.5^{\circ}\), and \(15^{\circ}\); and the calculation conditions of roll rotation angle include \(0^{\circ}\), \(2.5^{\circ}\), \(5^{\circ}\), \(7.5^{\circ}\), \(10^{\circ}\), \(12.5^{\circ}\), and \(15^{\circ}\).  
\end{table} 
Table 2: Posture parameters and calculation conditions during flight.