In this paper, we investigate experimentally the concept of energy harvesting from galloping oscillations with a focus on wake and turbulence effects. The harvester is composed of a unimorph piezoelectric cantilever beam with a square cross-section tip mass. In one case, the harvester is placed in the wake of another galloping harvester with the objective of determining the wake effects on the response of the harvester. In the second case, meshes were placed upstream of the harvester with the objective of investigating the effects of upstream turbulence on the response of the harvester. The results show that both wake effects and upstream turbulence significantly affect the response of the harvester. Depending on the spacing between the two squares and the opening size of the mesh, wake and upstream turbulence can positively enhance the level of the harvested power.Converting aeroelastic vibrations into electricity has been proposed for energy harvesters design that can be used to operate self-powered small electronic devices or to take the place of small batteries, which have a finite-life span or require expensive and hard maintenance. Depending on the operating wind speed, piezoaeroelastic energy harvesters can be designed and deployed in different locations, such as structure's surface, ventilation outlets, rivers, etc., to power sensors or actuators. Several investigations have focused on harvesting energy from flow-induced vibrations, such as vortex-induced vibrations of circular cylinders, 1-4 flutter of airfoil sections, 5-13 wake galloping, 14,15 and galloping of prismatic structures. [15][16][17][18][19][20][21][22] The transverse galloping phenomenon has shown a promise for effective energy harvesting. For instance Sirohi and Mahadik 16 reported that at a wind speed of 11.6 mph (1 mph = 0.447 m/s) most of the commercial wireless sensors can be supplied by their proposed piezoaeroelastic energy harvester. To design enhanced galloping-based piezoaeroelastic energy harvesters, Abdelkefi et al. 17-21 studied the effects of the cross-section geometry, Reynolds number, electrical load resistance, ambient temperature on the onset speed of galloping, and the harvested power's lever. Yang et al. 22 experimentally investigated the effects of the cross-section geometry on the performance of galloping-based piezoelectric energy harvesters.In all of the above studies, the harvesters were subjected to uniform wind speed. In this work, a) Corresponding author.

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The paper investigates the effect of the location and size of piezoelectric patches in a composite multilayer plate on the energy input/output when the plate acts as a sensor, actuator, or an energy harvester. It is shown that whether the process is low frequency (static) or higher frequency, for any size of the piezoelectric patches there is always one location where the energy input/output reaches a maximum. In addition, it is shown that for a dynamic vibrational loading the energy input/output is extremely sensitive to the operating frequency. If the operating frequency is just below the systems resonant frequency (corresponding to the length and position of the patches) the best location for the maximum energy input/output is significantly different from the best location when the operating frequency is just above the systems resonant frequency. In other words, a very small change in the systems operating frequency in the vicinity of the resonance frequency can make a significant effect on the best locations for the patches for the energy input/output.

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Micromechanics models of fiber kinking provide insight into the compressive failure mechanism of fiber reinforced composites, but are computationally inefficient in capturing the progressive damage and failure of the material. A homogenized model is desirable for this purpose. Yet, if a proper length scale is not incorporated into the continuum, the resulting implementation becomes mesh dependent when a numerical approach is used for computation. In this paper, a micropolar continuum is discussed to characterize the compressive failure of fiber composites dominated by kinking. Kink banding is an instability associated with a snap-back behavior in the load–displacement response, leading to the formation of a finite region of localized deformation. The challenge in modeling this mode of failure is the inherent geometric and matrix material nonlinearity that must be considered. To overcome the mesh dependency of numerical results, a length scale is naturally introduced when modeling the composite as a micropolar continuum. A new approach is presented to approximate the effective transversely isotropic micropolar constitutive relation of a fiber composite. Using an updated Lagrangian, nonlinear finite element code, previously developed for incorporating the additional rotational degrees-of-freedom (DOFs) of micropolar theory, the simulation of localized deformation in a continuum model, corresponding to fiber kinking, is demonstrated and is found to be comparable with the micromechanics simulation results. Most importantly, the elusive kink band width is a natural outcome of the continuum model.