Flow kinetic energy conversion from vibration of cylinder arrays due to fluidelastic instability

Abstract

This research deals with the fluid-dynamic excitation of vibrations of cylinder arrays subjected to cross-flow due to the mechanism known as Fluidelastic Instability (FI). In this phenomenon, the cross-flow and the cylinders become a dynamically unstable system, i. e., with negative net–damping, when the velocity of the cross-flow exceeds a certain critical value [1]. F I has been responsible for self-excited vibrations with large amplitude in industrial equipment such as shell-and–tube heat exchangers. Because of its potential for the damage of the tubes, the phenomenon has been extensively investigated in the past in order to obtain correlations that can be used to predict critical velocity of the cross-flow at the design stage. However, the complexity of the flow-structure interactions involved produces a considerable uncertainly in those correlations so that large security coefficients have to be used to avoid F I in practise. Nevertheless, the F.I. phenomena also arises the possibility for a controlled extraction of kinetic energy from fluid streams, by conversion to mechanical energy in the vibrating cylinders and subsequent conversion to electrical energy. This is the purpose of the current investigation undertaken by the authors. It represents a novel application in line with some other recent studies on the flow-induced vibrations of cylindrical structures by vortex-shedding mechanisms as a renewable energy technology.