The dynamic flight stability of hovering insects includes the longitudinal and lateral motion.Research results have shown that for the majority of hovering insects the same longitudinal natural modes are identified an...The dynamic flight stability of hovering insects includes the longitudinal and lateral motion.Research results have shown that for the majority of hovering insects the same longitudinal natural modes are identified and the hovering flight in longitudinal is unstable.However,in lateral,the modal structure for hovering insects could be different and the stability property of lateral disturbance motion is not as robust as that of longitudinal motion.The cranefly possesses larger aspect ratio and lower Reynolds number,and such differences in morphology and kinematics may make the lateral dynamic stability different.In this paper,the lateral flight stability of the cranefly in hover is investigated by numerical simulation.Firstly,the stability derivatives are acquired by solving the incompressible Navier–Stokes equations.Subsequently,the dynamic stability characteristics are checked by analyzing the eigenvalues and eigenvectors of the linearized system.Computational results indicate that the lateral dynamic modal structure of cranefly is different from most other insects,consisting of three natural modes,and the weakly oscillatory mode illustrates the hovering lateral flight is nearly neutral.This neutral stability is mainly caused by the negative derivative of roll-moment vs.sideslip-velocity,which can be attributed to the weaker‘changingLEV-axial-velocity’effect.These results suggest that insects in nature may exhibit different dynamic stabilities with different morphological and kinematic parameters,which should be considered in the designs of flapping wing air vehicles.展开更多
Two new fossil subgenera and two new fossil species of the genus Tipula Linnaeus,1758,Tipula(Succinica)berendti subgen.and sp.n.and Tipula(Gedanica)adamowiczi subgen.and sp.n.,are described from Baltic amber and compa...Two new fossil subgenera and two new fossil species of the genus Tipula Linnaeus,1758,Tipula(Succinica)berendti subgen.and sp.n.and Tipula(Gedanica)adamowiczi subgen.and sp.n.,are described from Baltic amber and compared with other species of Tipula known from the Eocene.The two new subgenera and species described herein are an excellent bridge between recent specimens and those preserved in sedimentary rocks,and thus enrich knowledge on the evolution of the family.展开更多
基金This work was supported by grants from the National Natural Science Foundation of China(Nos.11802262 and 11502228).
文摘The dynamic flight stability of hovering insects includes the longitudinal and lateral motion.Research results have shown that for the majority of hovering insects the same longitudinal natural modes are identified and the hovering flight in longitudinal is unstable.However,in lateral,the modal structure for hovering insects could be different and the stability property of lateral disturbance motion is not as robust as that of longitudinal motion.The cranefly possesses larger aspect ratio and lower Reynolds number,and such differences in morphology and kinematics may make the lateral dynamic stability different.In this paper,the lateral flight stability of the cranefly in hover is investigated by numerical simulation.Firstly,the stability derivatives are acquired by solving the incompressible Navier–Stokes equations.Subsequently,the dynamic stability characteristics are checked by analyzing the eigenvalues and eigenvectors of the linearized system.Computational results indicate that the lateral dynamic modal structure of cranefly is different from most other insects,consisting of three natural modes,and the weakly oscillatory mode illustrates the hovering lateral flight is nearly neutral.This neutral stability is mainly caused by the negative derivative of roll-moment vs.sideslip-velocity,which can be attributed to the weaker‘changingLEV-axial-velocity’effect.These results suggest that insects in nature may exhibit different dynamic stabilities with different morphological and kinematic parameters,which should be considered in the designs of flapping wing air vehicles.
基金This project was supported in part by an ISEA PAS grant(no.6085/E-47/M/2017)
文摘Two new fossil subgenera and two new fossil species of the genus Tipula Linnaeus,1758,Tipula(Succinica)berendti subgen.and sp.n.and Tipula(Gedanica)adamowiczi subgen.and sp.n.,are described from Baltic amber and compared with other species of Tipula known from the Eocene.The two new subgenera and species described herein are an excellent bridge between recent specimens and those preserved in sedimentary rocks,and thus enrich knowledge on the evolution of the family.
