Optimization of Ski Attitude for the In-Flight Aerodynamic Performance of Ski Jumping

SIMPLE SUMMARY: Flight distance determines the score of ski jumping and thus should be elongated in the competitions. Research has found that an analysis of aerodynamics is indispensable for ski jumping and the attitudes of athletes and skis are crucial factors to dictate the aerodynamic forces. As a follow-up to our previous computational fluid dynamics work, an optimization of the ski attitudes is conducted to maximize the lift-to-drag ratio under certain lift constraints. The optimal attitudes at these lift levels are of practical importance for athlete training and the angle of attack is proven to be pivotal for the optimal lift-to-drag ratio. The flow structures generated by the ski at the optimal attitudes are also discussed, together with a comparison with previous wind-tunnel measurements. ABSTRACT: The control and adjustment of in-flight attitudes are critical to enlarging the flight distance of ski jumping. As one of the most important gears, the skis provide sufficient lift and drag forces for the athletes, and thus their in-flight attitudes should be optimized to improve flight performance. Here, the lift-to-drag ratio of a ski jumping ski is optimized with/without a constraint of lift capacity. The ski attitude is defined by three Eulerian angles and the resulting aerodynamic characteristics are predicted by Kriging models, which are established based on computational fluid dynamics (CFD) data. The surrogated models are dynamically updated in the optimization process to ensure their accuracy. Our results find that the optimization of the lift-to-drag ratio should be constrained by a certain lift capacity to be more practical. The angle of attack of the ski dominates the optimal lift-to-drag ratio at different lift levels while the yaw and roll angles are almost independent of the constraint once the required lift coefficient surpasses 0.6. This thus suggests that the athletes should focus on the angle of attack when modifying the ski attitude in the flight, which may reduce the difficulties in their in-flight decision makings.