The Woodruff School

SUMMARY

We design and build a tabletop wind energy harvester inspired by the swaying of trees. The device consists of cantilevered cylinders ("tree trunks") arranged linearly downwind. The bases of the cylinders contain piezoelectric transducers that capture energy from vibration of the cylinder transverse to the flow. For a particular Reynolds number, and ratio of vortex shedding frequency to cylinder natural frequency, we experimentally measure the power generated (~1 micro-watt) as a function of cylinder arrangement. We report optimal spacings for generating peak power. We also report the distribution of power down the array. We qualitatively account for these trends using flow visualizations of vortex shedding using a flowing soap film dynamically matched with our piezoelectric system.

SUBJECT:	M.S. Thesis Presentation

BY:	William Hobbs

TIME:	Monday, March 29, 2010, 11:00 a.m.

PLACE:	MRDC Building, 4211

TITLE:	Piezoelectric Energy Harvesting: Vortex Induced Vibrations in Plants, Soap Films, and Arrays of Cylinders

COMMITTEE:	Dr. David Hu, Co-Chair (ME) Dr. Alexander Alexeev, Co-Chair (ME) Dr. Silas Alben (MATH)

SUMMARY We design and build a tabletop wind energy harvester inspired by the swaying of trees. The device consists of cantilevered cylinders ("tree trunks") arranged linearly downwind. The bases of the cylinders contain piezoelectric transducers that capture energy from vibration of the cylinder transverse to the flow. For a particular Reynolds number, and ratio of vortex shedding frequency to cylinder natural frequency, we experimentally measure the power generated (~1 micro-watt) as a function of cylinder arrangement. We report optimal spacings for generating peak power. We also report the distribution of power down the array. We qualitatively account for these trends using flow visualizations of vortex shedding using a flowing soap film dynamically matched with our piezoelectric system.