Investigation into energy harvesting from a non-linear aeroelastic system subjected to stochastic loads

There is growing interest to harvest energy from aeroelastic oscillations — with the goal of making several small power devices self-reliant. While a considerable success has been achieved in understanding the optimal range of parameters required for succinct aeroelastic energy harvesting, translating these developments to in-field conditions is fraught with difficulties. A prominent challenge that is ubiquitous in in-field conditions is the presence of ambient wind fluctuations. These wind fluctuations are often random and vary across different scales of spatial and temporal variables. Further, from an aerodynamic point of view, these stochastic wind fluctuations could either be axial, i.e., along the direction of the chord line of the airfoil, or could be in the vertical direction, i.e., perpendicular to the chord line of the airfoil. The former gives rise to a multiplicative noise, and the latter yields to be an additive noise to the existing dynamical system (airfoil). The energy harvesting potential under these stochastic wind gusts is minimally explored in the hitherto literature and are far from complete. Addressing this end-of-concern forms the pivotal focus of this study. To that end, a pitch–plunge airfoil with cubic hardening nonlinearity in the pitch stiffness is considered. A piezoelectric transducer (PZT) is attached to the elastic axis of the airfoil. A numerical approach is used to solve the aeroelastic system coupled with an energy harvesting mechanism undergoing stochastic wind fluctuations to determine the voltage output and the harvested power. As a first step, the deterministic bifurcation scenario, along with the energy harvesting potential, is presented. Subsequently, the energy harvesting potential under longitudinal turbulence, vertical turbulence, and combined longitudinal and vertical turbulence is provided. Results indicate that vertical turbulence, in particular, produces continuous oscillations even below the so-called flutter velocity, enabling effective energy harvesting capabilities unlike its longitudinal counterpart. Given the ubiquitous presence of vertical wind gusts and a variety of aeroelastic devices, the findings from this study underscore the impact of various turbulence components on power output, along with offering insights into optimizing energy harvesting for real-world applications.