Chapter 10 On the Dynamic Response of Flow-Induced Vibration of Nonlinear Structures Banafsheh Seyed-Aghazadeh, Hamed Samandari, and Reza Abrisham Baf Abstract Fundamentals of Fluid-Structure Interaction (FSI) of a nonlinear structure placed in the wake of a prismatic bluff body is studied, experimentally. Elastically mounted prismatic structures placed in flow can undergo Flow-Induced Vibration (FIV). Flow forces acting on these structures consist of a main frequency, close to the natural frequency of the system, as well as its higher harmonic components. Mostly in FIV studies, the structural stiffness is provided through linear springs. The linearity of the structure limits occurrence of potential large amplitude oscillations at higher harmonics of the main frequency. In this study, an inherently nonlinear structure is implemented in FIV study of a prismatic structure. The results show that large amplitude, low frequency galloping type oscillation is accompanied by large contributions from the higher harmonics in the frequency content of the oscillations. Numerical simulation using Differential Quadrature Method was conducted to identify the optimum structural configurations for coupling between the higher harmonics and natural frequencies of the system. Keywords Flow-induced vibration · Fluidic energy harvester · Nonlinear structure · Fluid-structure interactions · Higher harmonics 10.1 Introduction Converting vibrations to usable form of electrical energy has been the subject of several studies over the past few years [1–3]. Research into energy harvesting started with the fundamental efforts for converting simple harmonic vibrations into electricity. However, in the last couple of years, research efforts have focused on converting other forms of mechanical energy, such as random ambient vibrations, surface strain energy of civil engineering structures and vibration induced by wind and water flow. On this basis, energy harvesters from vibration induced by flow energy have been proposed to operate self-powered devices including micro-electro-mechanical systems and wireless sensors. They are also designed to replace small batteries that have a finite life span or would require expensive and time-consuming maintenance. When a flexible or flexibly mounted structure is placed in fluid flow, it can deform or oscillate. The deformation or oscillation of the structure will result in the change of flow forces, which in turn will result in the change of the structure’s deformation or oscillation. This oscillation is called Flow-Induced Vibration (FIV). The most common fluidic energy harvester works based on Flow-Induced Vibration that can harvest energy from external sources available in the environment such as wind or marine currents. There are several studies on FIV with applications in wind energy with novel energy extraction ideas [4–8]. Most common fluidic energy harvesters consist of a piezoelectric cantilevered beam, clamped at one end, connected to a rigid prism with a specific cross-section at the free end, placed in flow. When the vortex formation frequency in the wake of the prism is relatively close to the beam’s modal frequencies (usually the first), FIV will occur. The oscillation will cause large strain near the clamped end. The strain produces a voltage difference in the piezoelectric patches and a circuit converts the electric potential to a current. Flow forces acting on the structure undergoing FIV consists of the main frequency, close to B. Seyed-Aghazadeh ( ) Department of Engineering Technology, Miami University, Middletown, OH, USA e-mail: seyedab@miamioh.edu H. Samandari Department of Mechanical and Manufacturing Engineering, Miami University, Oxford, OH, USA R. Abrisham Baf Department of Engineering Technology, Miami University, Hamilton, OH, USA © Society for Experimental Mechanics, Inc. 2020 G. Kerschen et al. (eds.), Nonlinear Structures and Systems, Volume 1, Conference Proceedings of the Society for Experimental Mechanics Series, https://doi.org/10.1007/978-3-030-12391-8_10 91
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