Flapping wings are important in many biological and bioinspired systems. Here, we investigate the fluid mechanics of flapping wings that possess a single flexible hinge allowing passive wing pitch rotation under load. We perform experiments on an insect-scale (≈1 cm wing span) robotic flapper and compare the results with a quasi-steady dynamical model and a coupled fluid–structure computational...

Changes in muscle activation patterns can lead to new locomotor modes; however, neuromotor conservation-the evolution of new forms of locomotion through changes in structure without concurrent changes to underlying motor patterns-has been documented across diverse styles of locomotion. Animals that swim using appendages do so via rowing (anteroposterior oscilations) or flapping (dorsoventral os...

Many insects and some birds can hover in place using flapping wing motion. Although this ability is key to making small scale aircraft, hovering flapping behavior has been difficult to reproduce artificially due to the challenging stability, power, and aeroelastic phenomena involved. A number of ornithopters have been demonstrated, some even as toys, nearly all of these designs, however, cannot...

In this paper, we investigate power flow in compliant mechanisms that are employed in dynamic applications. More specifically, we identify various elements of the energy storage and transfer between the input, external load, and strain energy stored within the compliant transmission. The goal is to design compliant mechanisms for dynamic applications by exploiting the inherent energy storage ca...

The effect of a wind gust on the aerodynamic characteristics of a rigid wing undergoing insect-based flapping motion is studied numerically. The turbulent flow near the flapping wing is described by the 3-D unsteady compressible Reynolds-Averaged Navier-Stokes equations with the Spalart-Allmaras turbulence model. The governing equations are solved using a second-order node-centered finite volum...

This paper presents a production study of incomplete neutralization in American English flapping. In flapping, /d/ and /t/ both become a voiced flap in certain prosodic contexts (see, e.g., Kahn 1980). A number of studies show that this neutralization is incomplete: /d/-flaps can be distinguished from /t/-flaps on the surface (Fox and Terbeek 1977). Other studies, however, have found conflictin...

For nocturnal insects, predation by bats can turn a moonlight flight into a nightmare. Moths have a way of avoiding bats, however, in the form of ultrasonic hearing. Because they have 'tympanal' ears, they can hear the echolocation calls of incoming bats and take evasive action. Butterflies, which are mainly diurnal, have not been known to have ultrasonic hearing. But these images from an unusu...

Miniature flapping flight systems hold great promise in matching the agility of their natural counterparts, bees, flies, and hummingbirds. Characterized by reciprocating wing motion, unsteady aerodynamics, and the ability to hover, insect-like flapping flight presents an interesting locomotion strategy capable of functioning at small size scales and is still a current focus of research. A vehic...

The capability of flapping wings to generate lift is currently evaluated by using the lift coefficient CL, a dimensionless number that is derived from the basal equation that calculates the steady-state lift coefficient CL for fixed wings. In contrast to its simple and direct application to fixed wings, the equation for CL requires prior knowledge of the flow field along the wing span, which re...

A method based on the power series solution is proposed to solve the natural frequency of flapping vibration for the rotating inclined Euler beam with constant angular velocity. The vibration of the rotating beam is measured from the position of the corresponding steady state axial deformation. In this paper the governing equations for linear vibration of a rotating Euler beam are derived by th...