Flutter Instability in an Internal Flow Energy Harvester

TL;DR

This paper investigates the flutter instability in an internal flow energy harvester, combining experiments and modeling to understand the mechanism and provide a foundation for improved device design.

Contribution

It introduces a generalized model based on flow-rate modulation that accurately predicts flutter onset and mode shapes, advancing the understanding of flow-induced vibrations in energy harvesters.

Findings

Flow modulation through the channel throat drives flutter.

The model accurately predicts flutter onset and mode shapes.

The generalized model aids in designing more effective energy harvesters.

Abstract

Vibration-based flow energy harvesting enables robust, in-situ energy extraction for low-power applications, such as distributed sensor networks. Fluid-structure instabilities dictate a harvester's viability since the structural response to the flow determines its power output. Previous work on a flextensional-based flow energy harvester demonstrated that an elastic member within a converging-diverging channel is susceptible to the aeroelastic flutter. This work explores the mechanism driving flutter through experiments and simulations. A model is then developed based on channel flow-rate modulation and considering the effects of both normal and spanwise flow confinement on the instability. Linear stability analysis of the model replicates flutter onset, critical frequency, and mode shapes observed in experiments. The model suggests that flow modulation through the channel throat is the principal mechanism for the fluid-induced vibration. The generalized model presented can serve as the foundation of design parameter exploration for energy harvesters, perhaps leading to more powerful devices in the future, but also to other similar flow geometries where the flutter instability arises in an elastic member within a narrow flow passage.