The concept of harvesting energy from flow-induced vibrations has received a great deal of attention in the last few years. This technology would help in the replacement of small batteries that require expensive and time consuming maintenance and development of self-powered electronic devices, such as health monitoring sensors, medical implants, data transmitters, wireless sensors, and cameras. In this chapter, a particular focus is paid to the concept of harvesting energy from aeroelastic instabilities, such as flutter in airfoil sections, vortex-induced vibrations in circular cylinders, and galloping in prismatic structures. Nonlinear electroaeroelastic models for these energy harvesters are derived and validated with experimental measurements. It is shown how linear and nonlinear analyses can be used to breach traditional barriers in the design and performance enhancement of these aeroelastic energy harvesters, characterization of their behaviors, and identification of the contribution of different types of nonlinearities.
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Energy harvesting through conversion of wasted mechanical energy to electrical power has received growing attention in the last few years (Sodano, Park, & Inman, 2004; Beeby, Tudor, & White, 2006; Anton & Sodano, 2007; Cook-Chennault, Thambi, & Sastry, 2008; Tang & Yang, 2012; Abdelkefi, 2012). The ultimate goal in this research field is to power sensors or electronic devices by converting ambient energy. This technology is useful in wireless applications in which external battery charging requires expensive and time consuming maintenance. This technology could also potentially extend the missions of such aircraft systems, such as unmanned air vehicles (UAVs) and micro air vehicles (MAVs) (Magoteaux, Sanders, & Sodano, 2008; Abdelkefi & Ghommem, 2013). These harvesters can be deployed in many locations including urban areas, high wind areas, ventilation outlets, rivers, ducts of buildings, lifting components in aircraft structures, etc. Although different transduction mechanisms can be used to convert wasted mechanical vibrations to electrical energy, piezoelectric transduction has been deemed the most suitable option for small devices because it can be placed in small volumes and used over a wide range of frequencies. In addition, the piezoelectric transduction does not need an external input voltage.
To harvest energy from wasted mechanical energy available in the environment, several concepts have been proposed. The most common concept consists of a unimorph or bimorph piezoelectric cantilever beam subjected to external excitations applied at its base. Resonant motions are obtained and then converted to electrical energy when the excitation frequency matches the natural frequency of the harvester. In their review paper, Anton & Sodano (2007) presented and discussed different approaches to enhance the performance of these harvesters, such as the use of efficient piezoelectric materials, use of distinct mode coupling, and optimization of the power conditioning circuitry. For the same purpose, different other strategies have been introduced including multi-modal systems (Abdelkefi, Najar, Nayfeh, & Ben Ayed, 2011), beam geometry (Goldschmidtboeing & Woias, 2008; Ben Ayed, Abdelkefi, Najar, & Hajj, 2014; Rosa & De Marqui, 2014), magnetic coupling (Karami & Inman, 2011; Tang & Yang, 2012), and bistable configurations (Stanton, McGehee, & Mann, 2009; Karami & Inman, 2011; Masana & Daqaq, 2011).
The above studies focused on harvesting energy from base excitations. However, there have also been interest in the concept of harvesting energy from flow-induced vibrations including flutter of airfoil sections (Bryant & Garcia, 2009; Erturk, Vieira, De Marqui, & Inman, 2010; De Marqui, Erturk, & Inman, 2011; Sousa, de M Anicezio, De Marqui, & Erturk, 2011; Abdelkefi & Nuhait, 2013), vortex-induced vibrations (VIVs) of circular cylinders (Akaydin, Elvin, & Andreopoulos, 2010, 2012; Abdelkefi, Hajj, & Nayfeh, 2012a; Mehmood, Abdelkefi, Hajj, Nayfeh, Akhtar, & Nuhait, 2013; Mackowski & Williamson, 2013; Dai, Abdelkefi, & Wang, 2014), galloping of prismatic structures (Sirohi & Mahadik, 2011; Abdelkefi, Hajj, & Nayfeh, 2013a; Zhao, Tang, & Yang, 2013; Yang, Zhao, & Tang, 2013; Bibo & Daqaq, 2014), and wake galloping of parallel cylinders (Jung & Lee, 2011; Abdelkefi, Scanlon, McDowell, & Hajj, 2013b). In this concept, the piezoelectric energy harvester is placed in a flow field and excited to undergo large limit-cycle oscillation amplitudes that can be transformed to electrical energy. Depending on the operating flow speed, these piezoaeroelastic energy harvesters can be designed and deployed in different locations.