Nonlinear energy harvesting of a piezoelectric pipe conveying fluid integrating boundary and geometric nonlinearities

Abstract

To address the inherent narrow-bandwidth limitation of conventional linear energy harvesting, this study proposes a nonlinear fluid-structure interaction (FSI) energy harvester based on a bimorph pipe conveying fluid constrained by retaining clips, which introduces two distinct nonlinear mechanisms: i) boundary nonlinearity due to the equivalent nonlinear stiffness, and ii) geometric nonlinearity from the extensible centerline of the pipe. The electro-mechanical governing equations of such nonlinear FSI system are established via the Hamilton principle, whereby the complex eigenfrequencies are first obtained for stability analysis. The vibration and electrical responses are further attained to evaluate the energy harvesting performance. In particular, a novel supercritical analysis is conducted to predict the harvester behaviour under buckling and flutter instabilities. Numerical results demonstrate that the designed nonlinear harvester significantly improves the operational bandwidth, and its performance can be regulated by tuning various system parameters. Interestingly, the FSI effect contributes to a broader energy harvesting bandwidth in the low-frequency region, but leads to a reduced peak voltage in the flutter state. In addition to force excitation, displacement excitation is also concerned, under which a better energy harvesting performance is exhibited. However, high nonlinear stiffness in this pattern may result in numerical divergence.