Constructive interference in a network of elastically-bounded flapping plates

Abstract

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.

Direct numerical simulation of flapping flags in grid-induced turbulence

“…Instead, when the dynamics is fully governed by the resulting fluid-structure interaction (e.g., the flapping flag), the second method, which is based on a moving-least-squares (MLS) interpolation, is more effective in minimising the spurious numerical oscillations 54 . Both methods have been extensively validated and used for multiphase and biological FSI problems 10,49,52,53,55,56 .…”

“…Fluid-structure interaction (FSI) is ubiquitous and governs many physical problems with relevance in natural processes [1][2][3] and engineering applications [4][5][6][7][8][9][10] . A formidable and recently increased effort has been devoted to understand these problems in more detail and, in particular, characterise the aeroelastic instabilities leading to self-sustained, flow-induced oscillations [11][12][13][14] .…”

“…In FSI, the effect of turbulence can be crucial on triggering (or suppressing) the onset of aeroelastic instabilities and more generally altering the characteristics of the resulting flow-induced oscillations, thus affecting, e.g., the potential for energy harvesting 10,11,41 . In particular, here we focus on the three-dimensional flapping dynamics of a flexible flag, a problem attracting significant attention both from the fundamental and applied perspective 5,6,13,[42][43][44][45][46] , however so far substantially limited to the situation where the incoming flow is laminar.…”

A new phenomenon in interference effect on catamaran dynamic response

“…Moreover, decreasing distance between foils enhanced both thrust and efficiency [10][11][12]. Furthermore, by diminishing flow separation, extra thrust and efficiency will be generated if the foils in biplane arrangement are equipped with an auto-pitch mechanism along with an elastic pitching axis [13,14].…”

Universal flapping states of elastic fibers in modulated turbulence

“…The interaction between elastic objects and fluid flows plays an essential role in a variety of both fundamental and applied problems, ranging from biological (e.g., mucus-cilia or red blood cells hydrodynamics) 1-3 and environmental processes (e.g., flow in flexible canopies and plant reconfiguration) [4][5][6][7] to engineering applications (e.g., energy harvesting and flow control) [8][9][10][11][12][13][14] . Despite the great advancement of research in these fields, the available knowledge on such nontrivial phenomena mostly concerns the situation where the flow is laminar [15][16][17][18] , whereas the interaction between elastic objects and turbulence has started to be understood only more recently [19][20][21][22][23] .…”