Animals that swim using appendages do so by way of rowing and/or flapping motions. Often considered discrete categories, rowing and flapping are more appropriately regarded as points along a continuum. The pig-nosed turtle, Carettochelys insculpta, is unusual in that it is the only freshwater turtle to have limbs modified into flippers and swim via synchronous forelimb motions that resemble dor...

Control of ornithopters is challenging due to the unsteady flow generated by the flapping wings. The research presented in this paper is aimed at developing a sensor-based control methodology. Specifically, a distributed pressure sensing system embedded in the flapping wing surfaces is utilized to provide real-time aerodynamic force estimates to facilitate the development of feedback for an orn...

Optimization of flapping wing trajectory was explored using an experimental apparatus. A scaled-up hawkmoth (Manduca sexta) wing was fabricated and mounted to a three-degree of freedom flapping mechanism. The vertical force generated during flapping was measured using a load cell and the wing path was optimized to maximize the average vertical force. The mechanism design, control, and instrumen...

Stability and control of rotors at high advance ratio are considered. Stability of teetering, articulated, and gimbaled hub types is considered with a simple flapping blade analysis. Rotor control in autorotation for teetering and articulated hub types is examined in more detail for a compound helicopter (rotor and fixed wing) using the comprehensive analysis CAMRAD II. Autorotation is found to...

A brute-force testing technique was applied on a robotic controlled-curvature flapping fin propulsor to investigate output thrust and power consumption trends with respect to flapping frequency, amplitude, and gait. It has been discovered that maximum thrust and maximum propulsive efficiency can coexist, that flapping frequency and amplitude are sometimes interdependent parameters, and that act...

Recent work on the aerodynamics of flapping flight reveals fundamental differences in the mechanisms of aerodynamic force generation between fixed and flapping wings. When fixed wings translate at high angles of attack, they periodically generate and shed leading and trailing edge vortices as reflected in their fluctuating aerodynamic force traces and associated flow visualization. In contrast,...

The shape and motion of the pectoral fins vary considerably among fishes that swim in the labriform mode. Pectoral fin motion in fishes is highly variable, but one conspicuous axis of this variation is the rowing-flapping axis. At one extreme of this axis, paddle-shaped fins row back and forth in a plane that is parallel to fish motion, while at the other extreme, wing-shaped fins flap up and d...

Abstract: To propel a lightweight structure, a hybrid wing structure was designed; the wing’s geometry resembled a rotor blade, and its flexibility resembled an insect’s flapping wing. The wing was designed to be flexible in twist and spanwise rigid, thus maintaining the aeroelastic advantages of a flexible wing. The use of a relatively “thick” airfoil enabled the achievement of higher strength...

Flapping flight is ubiquitous in Nature, yet cilia and flagella, not wings, prevail in the world of micro-organisms. This paper addresses this dichotomy. We investigate experimentally the dynamics of a wing, flapped up and down and free to move horizontally. The wing begins to move forward spontaneously as a critical frequency is exceeded, indicating that ‘flapping flight’ occurs as a symmetry-...

In this paper we carry out computational studies of three-dimensional flow over flapping wings. The problems we have investigated include, firstly, three-dimensonal simulation of flow over an extruded SD7003 airfoil in plunging motion at transitional Reynolds number and, secondly, flow over a pair of flapping rectangle wings with constant NACA0012 cross-sectional airfoil profile at low Reynolds...