Energy-Harvesting Microresonator Based on the Forces Generated by the Karman Street Around a Rectangular Prism

This paper explores the feasibility of using the unsteady forces generated by the Karman street around a microprism in the laminar flow regime as a means to generate mechanical work. In particular, the study has the objective of assessing whether this physical effect could be used for practical energy-harvesting purposes. The confined flow, either of a liquid or a gas, around a rectangular microprism, of which different aspect ratios have been studied, is considered at Reynolds 200 so as to make sure that the Karman street is developed and that the flow remains 2-D. The microprism is allowed to move freely in the direction perpendicular to the flow. The equation of motion of the prism includes a term that simulates its coupling with a vibration-driven micropower generator. Two different couplings have been considered: a velocity-damped resonant generator and a Coulomb-damped resonant generator. Different configurations have been studied, and comparisons have been carried out between them so as to draw a first set of design guidelines. Finally, it is shown that this type of energy-harvesting microdevice, which is basically 2-D, would yield a reasonable compromise between power output, manufacturing simplicity, and cost.