基于风洞试验的奥运会RS:X级帆板摇帆推进特性研究
Research of the Propulsion Characteristics of Neil Pryde RS:X Pumping Based on Wind Tunnel
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摘要: 目的:探索帆翼摇帆因素(风速、攻角、频率和幅度)对帆翼气动特性和推进特性的影响。方法:通过低湍流度风洞和改装扑翼测控系统开展RS:X帆翼模型风洞试验,模拟实际比赛中帆翼在迎风航段滑行和以不同频率、幅度围绕前进方向正弦摇帆的情况。结果:在滑行状态下,帆翼气动力随攻角和风速增加而增大,风速在5 m/s和6 m/s时帆翼的升力系数接近,但风速为6 m/s时的阻力系数明显小于5 m/s时。在摇帆状态下,帆翼气动力特征符合周期性变化;升力随摇帆频率的升高而增大,阻力随摇帆频率升高呈小幅减小。航向角35°航行时,推力系数未随攻角增加明显增大,但存在相位差,瞬时能耗系数明显增大;增加摇帆频率或幅度可以提升帆翼推力特性,同时,瞬时能耗成倍增加,但摇帆频率的增加比幅度的增加所需能耗更高。结论:帆翼摇帆比滑行能更有效地改善帆翼的气动力;风速是影响滑行与摇帆状态下帆翼气动特性和推进特性的主要因素;运动员根据比赛中的风力调整攻角是保证帆翼可操纵性的基础;增加摇帆频率可提升帆翼推进特性,但瞬时能耗较大,需要运动员具备较强的身体素质和控帆能力。总之,摇帆频率和幅度的配合是帆翼高效能推进的保障。Abstract: Objective: Investigating the effects of pumping factors on the aerodynamic and propulsion characteristics of the sail wing.Methods: The experiment of RS: X wing model was conducted in the low turbulence wind tunnel and the system of modified flapping. Results: While planning, the aerodynamic force of the sail wing increased with the increasing of attack angle and wind speed. The lift coefficient of the sail wing was similar when the wind speed was 5 m/s and 6 m/s, but the drag coefficient was lower when the wind speed was 6 m/s than 5 m/s. While pumping, aerodynamic force of the sail wing changed periodically, the lift force increased and the drag force decreased slightly when the pumping frequency increased. As the course angle was 35°, the thrust coefficient had no increase when attack angle increased, but a phase difference was observed, the coefficient of instantaneous energy consumption cost increased obviously. The propulsion of the sail wing could be improved by increasing pumping frequency or amplitude. Meanwhile, the instantaneous energy consumption cost was doubled, but more energy consumption was needed when the pumping frequency was increased than that of pumping amplitude. Conclusions: The pumping could improve the aerodynamic force of the sail wing more effectively than planning, wind speed was the main factor affecting the characteristics of aerodynamic and propulsion. Adjusting the attack angle according to the wind-force during competition was the foundation to ensure the maneuverability of the sail wing. Increasing the frequency of pumping could improve the propulsion of the sail, but the instantaneous energy consumption cost was large, which required the athletes high levels of both physical fitness and ability of sail maneuverability. Briefly, coordination of the frequency and amplitude of the pumping guaranteed the high efficency propulsion of the sail wing.