Flow induced vibration on piezoelectric structures : theory, characterization, and application

• Main Author: Ewere, Felix E.
• Format: Text
• Language: unknown
• Published: LOUIS 2015
• Subjects: Airflow Sensor; Bluff Body Aerodynamics; Energy Harvesting; Flow-induced Vibration; Galloping Aeroelastic Instability; Piezoelectricity; Piezoelectric devices; Electric resonators; Vibration; Fluid dynamics; Humpback Whale
• Online Access: https://louis.uah.edu/uah-dissertations/79; https://louis.uah.edu/context/uah-dissertations/article/1078/viewcontent/ewere_10265.pdf

Harvesting energy using piezoelectric transduction has focused on vibration-based types that rely on ambient vibrations. The challenge is to identify a consistent vibration source which is essential for uninterrupted power. Wind energy can provide a reliable and sustained source of vibration to achieve these energy harvesting goals if flow-induced vibration on piezoelectric structures is carefully explored. In this dissertation, flow-induced vibration on piezoelectric structures is investigated based on the galloping piezoelectric energy harvester (GPEH) concept. A GPEH is composed of a cantilevered piezoelectric beam with a tip bluff body. Self-excited vibration is induced when the tip bluff body is subjected to airflow. Then, the piezoelectric materials can convert the mechanical energy into electrical energy. In order to understand the underlying physics, nonlinear coupled aero-electro-mechanical models are developed in which both geometric and material nonlinearities are considered. Dimensionless formulation is adopted so that it is convenient to conduct scaling and performance comparison of different galloping piezoelectric devices. Analytical approximate approach is employed to solve the nonlinear coupled equations using the Krylov-Bogoliubov method. This ensures that system parameters such as galloping velocity, limit cycle oscillation (LCO) amplitude, transient period, and harvested energy are determined accordingly and presented in an explicit form. Additionally, numerical studies are conducted using COMSOL Multiphysics. Several GPEH prototypes were fabricated. The baseline prototype is composed of a bimorph piezoelectric cantilever beam with a square cross-section bluff body. Subsequently, improved designs including addition of an impact bump stop to improve fatigue life and a bio-inspired tip bluff body borrowed from tubercles on flippers of the humpback whale. Comprehensive tests were conducted in a subsonic wind tunnel to determine system damping, electrical response, and LCO amplitude data. An ...