As a very basic flight mode, ascending flight is obviously of great importance to all kinds of manmade and natural fliers. Yet, for the most commonly seen fliers - insects, researches on this flight mode are rare. In ...As a very basic flight mode, ascending flight is obviously of great importance to all kinds of manmade and natural fliers. Yet, for the most commonly seen fliers - insects, researches on this flight mode are rare. In this paper, we combined both experimental measurements and numerical simulations to investigate the kinematical characteristics, aerodynamic performance and power requirement of ascending flight in fruit flies （Drosophila virilis）. The flies ascend at an advance ratio of about 0.12. The most significant characteristic of ascending flight is larger stroke amplitude compared to hovering, while the other kinematics is very similar. From an aerodynamics point of view, this increased stroke amplitude is needed to overcome the negative effects of＂downwash flow＂, caused by the upward motion of the fly. Same as hovering, the ascending fruit flies utilize delayed stall and fast pitching-up mechanisms to generate the majority of the lift required for balancing the weight and body drag. By using a larger stroke-amplitude to overcome the negative effects of＂downwash flow＂, larger energy cost （about 20%） than that of equivalent hovering is required.展开更多
基金This work was supported by a grant from the National Natural Science Foundation of China （11232002）.The author Yanpeng Liu also would like to acknowledge the supports from China Scholarship Council （CSC, 201306025020） and BMCE （YETP 1083）.
文摘As a very basic flight mode, ascending flight is obviously of great importance to all kinds of manmade and natural fliers. Yet, for the most commonly seen fliers - insects, researches on this flight mode are rare. In this paper, we combined both experimental measurements and numerical simulations to investigate the kinematical characteristics, aerodynamic performance and power requirement of ascending flight in fruit flies （Drosophila virilis）. The flies ascend at an advance ratio of about 0.12. The most significant characteristic of ascending flight is larger stroke amplitude compared to hovering, while the other kinematics is very similar. From an aerodynamics point of view, this increased stroke amplitude is needed to overcome the negative effects of＂downwash flow＂, caused by the upward motion of the fly. Same as hovering, the ascending fruit flies utilize delayed stall and fast pitching-up mechanisms to generate the majority of the lift required for balancing the weight and body drag. By using a larger stroke-amplitude to overcome the negative effects of＂downwash flow＂, larger energy cost （about 20%） than that of equivalent hovering is required.
