Aerodynamics Research Of A Flapping Wing

The development of micro air vehicles(MAV) has resulted in considerable interest on the aeromechanics of flapping wings because of the unique performance of biological flyers, which almost universally use flapping wing propulsion. Performance of MAV such as hover, maneuverability, agility and energy consumption are significantly better than conventional fixed wing vehicles.The aerodynamics of flapping wing of birds and insects are completely different from fixed wing. Based on the observation and research of many bionics scientists,the aerodynamics of flapping wings of insects, birds are discussed, which could produce high lift and thrust. In this paper, several kinematics based on an insect named Hawkmoth are designed and measured by using the force transducer. The flow structures around the flapping wings are observed by using flow visualization. Influence on aerodynamics of flapping wing by different pitch acceleration and pivot axis are discussed.The force and moment are measured when flapping wing is symmetrical kinematics, delayed kinematics and advanced kinematics of pitch angle. The experimental wing model is Zimmerman wing that is originated form the wing of Hawk moth. Three kinematics were named HM1(symmetrical kinematics), HM2(delayed kinematics) and HM3(advanced kinematics) respectively. Basing on the results of experiment, the paper pointed out that HM2 is the best kinematics for the wing model to produce the largest thrust and lift; HM3 is the worst kinematics that produced the smallest thrust and lift. Then, according to the experiment of the flow visualization, it is shown tha three kinematics could produce different dynamic characteristics.Usually the pitch angle of flapping wings of birds and insects have three phases: the first acceleration, uniform motion of middle phase and the final decadence.Four kinematics that have different acceleration named AM1, AM2, AM3 and AM4, are discussed and observed. The results showed that AM4 is the best kinematic because this kinematic could produce the largest thrust and lift. When the pitch angle of flapping wing accelerated, the LEV and TEV could be seen obviously in the flow field. The thrust and lift become larger. When the pitch angle of flapping wing hold for a while, the LEV and TEV would disappear. The thrust and lift become smaller.The pivot axis would also influence the dynamic characteristics obviously. When the pivot axis on the leading edge, the wing model would produce more thrust and lift. When the pivot axis on the mid-chord of the wing, the wing model would produce less thrust and lift.