Wideband PZT energy harvesting from the wake of a bluff body in varying flow speeds

Wake-galloping flow energy harvesters vibrate linearly under fluid force which results in a narrow lock-in region. Hence, their efficiency drops significantly in variable flow speeds leading to inevitable discrepancies between the natural frequency of the energy harvester and vortex shedding frequency. This sensitive dependence on the flow speed hinders the performance of this type of energy harvesters. This paper present a novel design of a PZT energy harvester for capturing energy from a broad range of vortex shedding frequencies associated with varying wind speeds. The proposed system composed of an array of bimorphs placed in the downstream of a bluff body. First, the nonlinear partial differential equations (PDEs) governing the dynamics of aero-electromechanical system are obtained based on Euler-Bernoulli assumption and nonlinear curvature effects. Next, the ordinary forms (ODEs) of the PDEs are attained using a Galerkin's Schemes. Moreover, they are non-dimensionalized to generalize the results and analyses; a convergence analysis has been carried out to find the minimum number of modes required to the precise prediction of the response. Exploiting harmonic balance method (HBM), the approximate-analytical solutions of the ODEs are provided. Afterward, the effects of various properties of the proposed ensemble on the lock-in region are investigated. In addition, the efficiency of the energy harvester is assessed toward examining its optimal power and conversion factor. The results disclose that the proposed system has a wider lock-in region and larger conversion factor, compared to the typical wake-galloping energy harvesters. Hence, the superior performance of the proposed design is confirmed.