Elastically bounded flapping wing for energy harvesting

Many technologies based on fluid-structure interaction mechanisms are being developed to harvest energy from geophysical flows. The velocity of such flows is low, and so is their energy density. Large systems are therefore required to extract a significant amount of energy. The question of the efficiency of energy harvesting using vortex-induced vibrations (VIV) of cables is addressed in this paper, through two reference configurations: (i) a long tensioned cable with periodically-distributed harvesters and (ii) a hanging cable with a single harvester at its upper extremity. After validation against either direct numerical simulations or experiments, an appropriate reduced-order wakeoscillator model is used to perform parametric studies of the impact of the harvesting parameters on the efficiency. For both configurations, an optimal set of parameters is identified and it is shown that the maximum efficiency is close to the value reached with an elastically-mounted rigid cylinder. The variability of the efficiency is studied in light of the fundamental properties of each configuration, i.e. body flexibility and gravity-induced spatial variation of the tension. In the periodically-distributed harvester configuration, it is found that the standing-wave nature of the vibration and structural mode selection play a central role in energy extraction. In contrast, the efficiency of the hanging cable is essentially driven by the occurrence of traveling wave vibrations.

Section: Introductionmentioning

confidence: 99%

On the efficiency of energy harvesting using vortex-induced vibrations of cables

Grouthier

Michelin

Bourguet

et al. 2014

“…In the new and challenging field of energy harvesting through fluid-structure instabilities, the coupled-mode flutter mechanism has been recently scrutinized (Peng and Zhu, 2009;Zhu, 2012;Boragno et al, 2012). A greater focus on post-critical behaviour is however necessary in order to improve the characterization, physical understanding and modeling of the large amplitude self-sustained vibrations resulting from these instabilities.…”

Section: Introductionmentioning

confidence: 99%

Low speed flutter and limit cycle oscillations of a two-degree-of-freedom flat plate in a wind tunnel

Amandolèse

Michelin

Choquel

2013

102

Amandolese, X., et al., Low speed flutter and limit cycle oscillations of a two-degree-offreedom flat plate in a wind tunnel. Journal of Fluids and Structures (2013) ABSTRACTThis paper explores the dynamical response of a two-degree-of-freedom flat plate undergoing classical coupled-mode flutter in a wind tunnel. Tests are performed at low Reynolds number (Re ~ 2.5×10 4 ), using an aeroelastic set-up that enables high amplitude pitch-plunge motion.Starting from rest and increasing the flow velocity, an unstable behaviour is first observed at the merging of frequencies: after a transient growth period the system enters a low amplitude limit-cycle oscillation regime with slowly varying amplitude. For higher velocity the system transitions to higher-amplitude and stable limit cycle oscillations (LCO) with an amplitude increasing with the flow velocity. Decreasing the velocity from this upper LCO branch the system remains in stable self-sustained oscillations down to 85% of the critical velocity.Starting from rest, the system can also move toward a stable LCO regime if a significant perturbation is imposed. Those results show that both the flutter boundary and post-critical behaviour are affected by nonlinear mechanisms. They also suggest that nonlinear aerodynamic effects play a significant role. KEYWORDS

“…16. Experiments were performed using the wind-tunnel facility at Physics Department of the University of Genoa, whose characteristic parameters, along with the procedure used to acquire the motion of flapping wings in time, have been described in previous works [26,28,30]. Each of the three components is similar to the devices already presented in Refs.…”

Section: Wind-tunnel Experimentsmentioning

confidence: 99%

Constructive interference in a network of elastically-bounded flapping plates

Olivieri

Boragno

Verzicco

et al. 2019

Self Cite

Aeroelastic phenomena are gaining significant attention from the perspective of energy harvesting (EH) with promising applications in supplying low-power remote sensors. Besides the development of individual EH devices, further issues are posed when considering multiple objects for realizing arrays of devices and magnifying the extracted power. Due to nonlinear mutual interactions, the resulting dynamics is generally different from that of single devices and the setup optimisation turns out to be nontrivial. In this work, we investigate the problem focusing on a flutter-based EH system consisting of a rigid plate anchored by elastic elements and invested by a uniform laminar flow, undergoing regular limit-cycle oscillations and flapping motions of finite amplitude. We consider a simplified, yet general, physical model and employ three-dimensional direct numerical simulations based on a finite-difference Navier-Stokes solver combined with a moving-least-squares immersed boundary method. Focusing on main kinematic and performancerelated quantities, we first report on the dynamics of the single device and then on multiple devices, considering different arrangements (i.e.: in-line, staggered and side-by-side). A parametric exploration is performed by varying the mutual distance between the devices and insights are provided. For the in-line arrangement, a recovery in performance for downstream devices is achieved by tuning their elasticity. Moreover, cooperative effects in the side-by-side arrangement are found to be substantially beneficial in terms of resulting power, with increases (i.e. constructive interference) up to 100% with respect to the single-device configuration. In order to confirm this numerical evidence, complementary results from wind-tunnel experiments are presented. Finally, we describe the system behaviour when increasing further the number of devices, outlining the ultimate goal of developing a high-performance EH network of numerous aeroelastic energy harvesters.