Meeting Abstract
80.1 Wednesday, Jan. 6 Aerodynamic Performance Enhancement by Insect Wing Flexibility NAKATA, T.*; LIU, H.; Chiba Univ., Japan; Chiba Univ., Japan nakata@graduate.chiba-u.jp
Insect wings are deformable structures that change shape passively and dynamically due to inertial and aerodynamic forces during flight and the flexibility of insect wings often leads to complex fluid-structure interactions. The effects of dynamic shape changes on unsteady aerodynamic force production in flapping flight are important in micro air vehicles but still remain unknown yet. To tackle this problem, a computational framework has been established by coupling an insect dynamic flight simulator (H. Liu, J. Comput. Phys., 2009) and a recently developed structural dynamics solver (T. Nakata et al., Comp. Biochem. Physiol. A, 2009). Geometric and kinematic models for a hovering hawkmoth, Manduca sexta are constructed on a basis of the measurement data (A.P. Willmott et al., J. Exp. Biol., 1997). Realistic stiffness of hawkmoth wings is taken into account, which are based on the rotational test results (S.A. Combes et al., J. Exp. Biol., 2003). The computational simulation clarified that the wing flexibility is apparently responsible for increasing the strength of the wake and hence the aerodynamic force. We further proposed a method to estimate the hovering efficiency and found a lift-up compared with that of a rigid wing model. The enhancement mechanisms are as follows: Firstly, the wing twist delays the shedding of the leading-edge vortex and hence augments the lift; Secondly, the curved and twisted wings are flattened and deformed in an opposite direction during the latter half of each stroke and then, the acceleration, the additional rotation and the phase advance of rotation (M.H. Dickinson et al., Science, 1999) at wing tip are induced. Our results imply that the kinematics of hawkmoth wings is very likely modified adaptively and the aerodynamic performance is enhanced automatically as a result of the wing deformation.
