Meeting Abstract

41.6  Saturday, Jan. 5  Fluid-solid coupled model of flapping flexing insect wings reveals multiple maxima for flight forces EBERLE, AL*; REINHALL, PG; MOUNTCASTLE, AM; DANIEL, TL; Univ. of Washington, Seattle; Univ. of Washington, Seattle; Harvard Univ., Boston; Univ. of Washington, Seattle

Many insect wings deform significantly during flight. This deformation is due to musculoskeletal forcing of the wing base, which results in passive emergent bending, along with aerodynamic loading of the surrounding fluid. Since deformation can change the amount of lift and thrust that the wing develops, the mechanical structure of the wing can influence flight performance. We explored two key issues associated with the design of compliant wings: over a range of driving frequencies, how does wing stiffness influence (1) the lift and thrust generated and (2) the relative importance of fluid loading. Since the parameter space is expansive, experimental methods and robotic realizations are not feasible. Thus, we developed a computational model that uses vortex methods and a spring-mass-damper model to couple the fluid loading to the structural dynamics. Actuation frequencies and flexural stiffnesses for the model were based on a range of values that encompass those measured for a number of insect taxa (4-80 Hz; 10-7-10-5 N m2). Over the entire range of parameters, we show that fluid loading never contributes more than 10% to the average flight forces. We also show a non-monotonic relationship for lift and thrust, which exhibits more than five local maxima over the same range of parameters. This non-monotonic relationship follows from several interacting periodic phenomena: elastic vibrations, oscillatory boundary conditions, and vortex shedding. As a result, for insect wings of any given stiffness or driving frequency, there exist multiple local maxima for lift and thrust.