The progress and challenges of aerodynamics in the bionic flapping-wing micro air vehicle

The bionic micro air vehicle (MAV )has important applications in military and civilian usage.In recent years,researchers over the world have revealed several unique flight mechanisms ,and developed several kinds of bionic micro air vehicles capable of certain flight abil-ities.In this paper,the aerodynamics progress in the bionic MAV is reviewed;also,the opportu-nity and challenges faced in the future are analyzed.At present,compared with the natural flyers,manmade bionic MAV is still clumsy and in a lower level,and thus has a large room for improvement.Many problems need to be tackled.The aerodynamics of low Reynolds number flow in unsteady state is one of the main problems.Since the flow is complex in this regime,the numerical simulation and the wind tunnel experiment can hardly model the situation of true flight.There are four concrete problems:(1 )the Reynolds number of bionic MAV flows is around 103~105 .In this regime,the transition and turbulence are easy to turn up,which makes the flow mechanism complex;(2 )the dynamic aero-elastic problem of flexible wing MAV in flight.In this situation,the scaling law is hard when the size is different for the structure and flow has different reference value.It is an essential problem to establish an accurate simulating model;(3 )the coupling problem of aero-elasticity and flight dynamics in high maneuverable flight;(4)the influence of flight attitude of flapping wing on the flight control system increases the complexity of feedback coupling control algorithm.These multi-disciplinary coupling problems make it a challenge to provide high accurate analysis for and improve the design of the bionic MAV.In the future,by solving the above problems,the bionic MAV should have high maneuver ability and can morph actively,like the natural flyers.