Modeling the capacity of a novel flow-energy harvester

Abstract

a b s t r a c tThe performance of a new type of flow energy harvester based on oscillating foils is investigated through numerical modeling by using two methods, a 2D thin-plate model and a 3D nonlinear boundary-element model. The fluid-structure interaction problem involved in the dynamics of a heaving/pitching foil coupled with an actuation/energy harvesting system in this device is examined. The 2D analysis allows us to simulate dynamics of the flapping-foil system over a large range of parameters and to identify areas of special interests (e.g., high energy output or high efficiency). In the vicinity of these areas the 3D model can accurately predict the performance of the system. By examining the power extraction capacity and efficiency of the system at various geometric, mechanical, and kinematic parameters, the optimal performance of the system is determined. In addition, the performance is found to be enhanced by the presence of a solid ground, as well as the thickness of the foil (at certain frequencies).

Energy harvesting from transverse galloping

“…As it is seen in Fig. 2a, once galloping is started, the normalized amplitude of oscillations increases with the reduced velocity, more dramatically for low values of a 3 . Conversely, Fig.…”

“…Fig. 3b shows the conversion factor dependence on ai and a 3 for fixed values of the mass and elastic properties and flow velocity. Based on this figure, it seems clear that in order to improve the power extraction it is needed to look for a cross-section with high values of ai and low absolute values of a 3 .…”

“…(8) with respect to the reduced velocity and equating to zero. After a little bit of algebra one obtains Sri, __8m*C(8m*C-a 1 l/*) &Th~ 3a 3 U* 3 ' and therefore,…”

“…4 can be redrawn beautifully (see Fig. 5) in a universal curve introducing the normalized variables ij = %/f/ Imax and 0 = U*/U*, being f/ Imax = -a\/(6a 3 ) and U* = 4m*(/a 1 . After a little of algebra one gets,…”

“…In their paper they analyze the key parameters to be controlled in order to achieve a practical design. The capacity of a flow-energy converter based on an oscillating foil is investigated in Zhu et al [3]. Inspired by the ability of fish to swim efficiently and extract energy from unsteady flows (to the extent that passive thrust generation becomes feasible in the wake of an upstream object [4]), they consider a foil with two degrees of freedom, heave and pitch, where the pitch motion is imposed by an actuator.…”