In the present paper, a numerical model to study the nonlinear and unsteady aerodynamics of morphing-wing concepts inspired by bird flight is developed. The model includes: i) a wing topology inspired by gull wings; ii) a kinematical model to describe the process of wing adaptation based on one mechanism observed in the flight of gulls (folding-wing approach); and iii) a version of the unsteady vortex-lattice methods (UVLM) that allows taking nonlinear and unsteady aerodynamic phenomena into account. The model was specially developed to study the aerodynamic behavior during wing adaptation. A simulation for a twisting-flapping wing was performed in order to validate the numerical model. The present results are in close agreement with those obtained in previous studies based on the Euler equations, but required much less execution time. The numerical simulations of a bioinspired morphing wing showed the strong dependence between the prescribed kinematics and the aerodynamic characteristics, which evidences the importance of studying the process of wing adaptation. UVLM is shown to be ideal for preliminary analysis of bioinspired morphing wings.

Converting flow-induced vibrations into electricity for low-power generation has received growing attention over the past few years. Aeroelastic phenomena, good candidates to yield high energy performance in renewable wind energy harvesting (EH) systems, can play a pivotal role in providing sufficient power for extended operation with little or no battery replacement. In this paper, a numerical model and a co-simulation approach have been developed to study a new EH device for power generation. We investigate the problem focusing on a weakly aerodynamically coupled flutter-based EH system. It consists of two flexible wings anchored by cantilevered beams with attached piezoelectric layers, undergoing nonlinear coupled bending–torsion limit cycle oscillations. Besides the development of individual EH devices, further issues are posed when considering multiple objects for realizing a network of devices and magnifying the extracted power due to nonlinear synergies and constructive interferences. This work investigates the effect of various external conditions and physical parameters on the performance of the piezoaeroelastic array of devices. From the viewpoint of applications, we are most concerned about whether an EH can generate sufficient power under a variable excitation. The results of this study can be used for the design and integration of low-energy wind generation technologies into buildings, bridges, and built-in sensor networks in aircraft structures.

A numerical-simulation tool is developed that is well suited for modeling the unsteady and nonlinear aerodynamics of flying insects and small birds as well as biologically inspired flapping-wing micro air vehicles (MAVs). The tool consists of a combination of (1) an aerodynamic model that is an extension of the widely used three-dimensional (3D) general unsteady vortex-lattice model, and (2) a general kinematic model that is capable of describing multiple deformation patterns of lifting surfaces, such as spanwise twisting, in-plane and out-of-plane bending, and any combination of these. Moreover, the present tool offers an attractive compromise between computational cost and fidelity and is ideally suited to be combined with computational structural dynamics to perform aeroelastic analyses. The present tool was successfully validated by comparing some of the present results with those obtained from existing numerical models based on both Euler equations and vortex-lattice codes and with some experimental data. Using the numerical framework developed and for the deformation mechanisms analyzed here, two distinctly different effects were found: the wing span’s twisting and in-plane bending affect the lift in specific zones of the stroke cycle (called “local behavior”); and the wing span’s out-of-plane bending affects the lift throughout the stroke cycle (called “global behavior”). In addition, the results found show that the wing’s flexibility certainly affects the lift production, at least for some flights at small scales. These findings definitely suggest the strong likelihood that the unsteady vortex-lattice method combined with a general kinematic model can be a very accurate and efficient tool for future aeroelastic studies.