Hummingbirds have a unique way of hover- ing. However, only a few published papers have gone into details of the corresponding three-dimensional vortex struc- tures and transient aerodynamic forces. In order to deepen...Hummingbirds have a unique way of hover- ing. However, only a few published papers have gone into details of the corresponding three-dimensional vortex struc- tures and transient aerodynamic forces. In order to deepen the understanding in these two realms, this article presents an integrated computational fluid dynamics study on the hovering aerodynamics of a rufous hummingbird. The original morphological and kinematic data came from a former researcher＇s experiments. We found that conical and sta- ble leading-edge vortices （LEVs） with spanwise flow inside their cores existed on the hovering hummingbird＇s wing surfaces. When the LEVs and other near-field vortices were all shed into the wake after stroke reversals, periodically shed bilateral vortex rings were formed. In addition, a strong downwash was present throughout the flapping cycle. Time histories of lift and drag were also obtained. Combining the three-dimensional flow field and time history of lift, we believe that high lift mechanisms （i.e., rotational circulation and wake capture） which take place at stroke reversals in insect flight was not evident here. For mean lift throughout a whole cycle, it is calculated to be 3.60 g （104.0 % of the weight support）. The downstroke and upstroke provide 64.2 % and 35.8 % of the weight support, respectively.展开更多
Animals that feed from resources that are constant in space and that refill may benefit from repeating the order in which they visit locations.This is a behavior known as traplining,a spatial phenomenon.Hummingbirds,l...Animals that feed from resources that are constant in space and that refill may benefit from repeating the order in which they visit locations.This is a behavior known as traplining,a spatial phenomenon.Hummingbirds,like other central-place foragers,use short traplines when moving between several rewarding sites.Here we investigated whether traplining hummingbirds also use relevant temporal information when choosing which flowers to visit.Wild rufous hummingbirds that were allowed to visit 3 artificial flower patches in which flowers were refilled 20 min after they had been depleted repeated the order in which they visited the 3 patches.Although they tended to visit the first 2 patches sooner than 20 min,they visited the third patch at approximately 20-min intervals.The time between visits to the patches increased across the experiment,suggesting that the birds learned to wait longer before visiting a patch.The birds appeared to couple the sequential pattern of a trapline with temporal regularity,to some degree.This suggests that there is a temporal component to the repeated spatial movements flown by foraging wild hummingbirds.展开更多
基金financially supported by the Supporting Foundation of the Ministry of Education (Grant 62501040303)the Pre-research Fund (Grants 9140A26020313JW03371, 9140A260204 14JW03412)the New Century Excellent Talents Support Program from the Ministry of Education of China (Grant NCET-10-0583)
文摘Hummingbirds have a unique way of hover- ing. However, only a few published papers have gone into details of the corresponding three-dimensional vortex struc- tures and transient aerodynamic forces. In order to deepen the understanding in these two realms, this article presents an integrated computational fluid dynamics study on the hovering aerodynamics of a rufous hummingbird. The original morphological and kinematic data came from a former researcher＇s experiments. We found that conical and sta- ble leading-edge vortices （LEVs） with spanwise flow inside their cores existed on the hovering hummingbird＇s wing surfaces. When the LEVs and other near-field vortices were all shed into the wake after stroke reversals, periodically shed bilateral vortex rings were formed. In addition, a strong downwash was present throughout the flapping cycle. Time histories of lift and drag were also obtained. Combining the three-dimensional flow field and time history of lift, we believe that high lift mechanisms （i.e., rotational circulation and wake capture） which take place at stroke reversals in insect flight was not evident here. For mean lift throughout a whole cycle, it is calculated to be 3.60 g （104.0 % of the weight support）. The downstroke and upstroke provide 64.2 % and 35.8 % of the weight support, respectively.
文摘Animals that feed from resources that are constant in space and that refill may benefit from repeating the order in which they visit locations.This is a behavior known as traplining,a spatial phenomenon.Hummingbirds,like other central-place foragers,use short traplines when moving between several rewarding sites.Here we investigated whether traplining hummingbirds also use relevant temporal information when choosing which flowers to visit.Wild rufous hummingbirds that were allowed to visit 3 artificial flower patches in which flowers were refilled 20 min after they had been depleted repeated the order in which they visited the 3 patches.Although they tended to visit the first 2 patches sooner than 20 min,they visited the third patch at approximately 20-min intervals.The time between visits to the patches increased across the experiment,suggesting that the birds learned to wait longer before visiting a patch.The birds appeared to couple the sequential pattern of a trapline with temporal regularity,to some degree.This suggests that there is a temporal component to the repeated spatial movements flown by foraging wild hummingbirds.
