Effects of wing deformation on aerodynamic performance of a revolving insect wing

Flexible wings of insects and bio-inspired micro air vehicles generally deform remarkably during flapping flight owing to aerodynamic and inertial forces, which is of highly nonlinear fluid-structure interaction (FSI) problems. To elucidate the novel mechanisms associated with flexible wing aerodynamics in the low Reynolds number regime, we have built up a FSI model of a hawkmoth wing undergoing revolving and made an investigation on the effects of flexible wing deformation on aerodynamic performance of the revolving wing model. To take into account the characteristics of flapping wing kinematics we designed a kinematic model for the revolving wing in two-fold: acceleration and steady rotation, which are based on hovering wing kinematics of hawkmoth, Manduca sexta. Our results show that both aerodynamic and inertial forces demonstrate a pronounced increase during acceleration phase, which results in a significant wing deformation. While the aerodynamic force turns to reduce after the wing acceleration terminates due to the burst and detachment of leading-edge vortices (LEVs), the dynamic wing deformation seem to delay the burst of LEVs and hence to augment the aerodynamic force during and even after the acceleration. During the phase of steady rotation, the flexible wing model generates more vertical force at higher angles of attack (40°–60°) but less horizontal force than those of a rigid wing model. This is because the wing twist in spanwise owing to aerodynamic forces results in a reduction in the effective angle of attack at wing tip, which leads to enhancing the aerodynamics performance by increasing the vertical force while reducing the horizontal force. Moreover, our results point out the importance of the fluid-structure interaction in evaluating flexible wing aerodynamics: the wing deformation does play a significant role in enhancing the aerodynamic performances but works differently during acceleration and steady rotation, which is mainly induced by inertial force in acceleration but by aerodynamic forces in steady rotation.

[1]  Mao Sun,et al.  Effects of wing deformation on aerodynamic forces in hovering hoverflies , 2010, Journal of Experimental Biology.

[2]  Stephen Ekwaro-Osire,et al.  Performance of an anisotropic Allman/DKT 3-node thin triangular flat shell element☆ , 1992 .

[3]  John Young,et al.  Details of Insect Wing Design and Deformation Enhance Aerodynamic Function and Flight Efficiency , 2009, Science.

[4]  J. Usherwood,et al.  The aerodynamics of revolving wings I. Model hawkmoth wings. , 2002, The Journal of experimental biology.

[5]  Rakesh K. Kapania,et al.  Updated Lagrangian Formulation of a Flat Triangular Element for Thin Laminated Shells , 1998 .

[6]  C. Ellington.  The Aerodynamics of Hovering Insect Flight. II. Morphological Parameters , 1984 .

[7]  Toshiyuki Nakata,et al.  A fluid-structure interaction model of insect flight with flexible wings , 2012, J. Comput. Phys..

[8]  M. Thompson,et al.  Reynolds number and aspect ratio effects on the leading-edge vortex for rotating insect wing planforms , 2013, Journal of Fluid Mechanics.

[9]  Andrew M. Mountcastle,et al.  Wing flexibility enhances load-lifting capacity in bumblebees , 2013, Proceedings of the Royal Society B: Biological Sciences.

[10]  M. Dickinson,et al.  Rotational accelerations stabilize leading edge vortices on revolving fly wings , 2009, Journal of Experimental Biology.

[11]  J. Usherwood,et al.  The aerodynamics of revolving wings II. Propeller force coefficients from mayfly to quail. , 2002, The Journal of experimental biology.

[12]  J. P. Whitney,et al.  Effect of flexural and torsional wing flexibility on lift generation in hoverfly flight. , 2011, Integrative and comparative biology.

[13]  K. Kawachi,et al.  A Numerical Study of Insect Flight , 1998 .

[14]  K. Bathe,et al.  FINITE ELEMENT FORMULATIONS FOR LARGE DEFORMATION DYNAMIC ANALYSIS , 1975 .

[15]  R. Mittal,et al.  Time-Varying Wing-Twist Improves Aerodynamic Efficiency of Forward Flight in Butterflies , 2013, PloS one.

[16]  M. Thompson,et al.  Relationship between aerodynamic forces, flow structures and wing camber for rotating insect wing planforms , 2013, Journal of Fluid Mechanics.

[17]  R Mittal,et al.  A comparative study of the hovering efficiency of flapping and revolving wings , 2013, Bioinspiration & biomimetics.

[18]  Toshiyuki Nakata,et al.  Aerodynamic performance of a hovering hawkmoth with flexible wings: a computational approach , 2012, Proceedings of the Royal Society B: Biological Sciences.

[19]  T. Daniel,et al.  Into thin air: contributions of aerodynamic and inertial-elastic forces to wing bending in the hawkmoth Manduca sexta , 2003, Journal of Experimental Biology.

[20]  C. Ellington,et al.  The mechanics of flight in the hawkmoth Manduca sexta. I. Kinematics of hovering and forward flight. , 1997, The Journal of experimental biology.

[21]  Hao Liu,et al.  Integrated modeling of insect flight: From morphology, kinematics to aerodynamics , 2009, J. Comput. Phys..

[22]  Ellington,et al.  A computational fluid dynamic study of hawkmoth hovering , 1998, The Journal of experimental biology.

[23]  M. Dickinson,et al.  Wing rotation and the aerodynamic basis of insect flight. , 1999, Science.

[24]  Hikaru Aono,et al.  Vortical Structure and Aerodynamics of Hawkmoth Hovering , 2006 .