A Study of Multi-Component Oscillating-Foil Hydrokinetic Turbines with a GPU-Accelerated Boundary Element Method

Abstract

A biomimetic semi-activated oscillating-foil device with multiple foils in a parallel configuration is studied for the extraction of marine renewable energy. For the present investigation, an unsteady boundary element method (BEM) is used for the simulation of 3D lifting flows. For this work, the device is assumed to be submerged far from the free surface and the sea bottom. However, the geometry of the body and the initial shape of the wake are general. For the numerical simulations, a high performance in-house GPU-accelerated code (GPU-BEM) is developed. For the calculation of singular integrals, an adaptive algorithm based on the Gauss-Lobatto quadrature is used. Concerning the numerical scheme of GPU-BEM, the convergence of the method was tested, the numerical characteristics were determined and the method was validated. A parametric study of a single-foil device is presented to determine the performance characteristics of such devices. Next, twin-foil devices are investigated in parallel and staggered configurations with a phase difference between the two foils. Finally, the multiple-foil parallel configuration is compared against turbines. After enhancement and further verification, the present method is proposed for the design and control of such biomimetic devices for the extraction of energy from waves and tidal currents nearshore.Foils can also be used as devices that convert tidal stream energy to other forms, i.e., electricity. In tidal energy harvesting mode, oscillating foils operate by absorbing energy from the incident current. One of the first reports on such designs is that of reference [15], and some early experiments were conducted in 1982 [16].Oscillating foils combine a pitch motion and a heave motion. In reference [17], oscillating-foil devices are classified into three categories depending on the activation mechanism of the oscillating foil. First, there are fully activated foils, where both the pitch and heave motions are prescribed. Second, there are semi-activated foils, where the pitch motion is given as input and the heave is the response to the hydrodynamic forces. Third, there are fully passive foils, where both motions are driven by the forces acting on the foil. In the present work, we study the semi-activated oscillating foil, because this alternative is a more feasible design than the fully activated system and it provides a mechanism to actively control the operation of the foils, in contrast to the fully passive design. Also, energy extraction of both waves and current is studied by the authors in [18].Moreover, efforts have been made to map the performance of oscillating foils in the energy extraction regime, i.e., parametric studies [19][20][21]. The basic parameters of the harmonic pitching motion have been mainly investigated, through experiments or numerical simulations. In [19], the authors report a power-extraction efficiency of 36.4% for a pitching amplitude of 76.3 degrees, using the FLUENT commercial software.Various studies have shown that oscillating foils can have...

A Non-Linear BEM–FEM Coupled Scheme for the Performance of Flexible Flapping-Foil Thrusters

“…Direct extensions include modelling various nonlinearities associated with large deflections and viscous effects [37,53]. Another aspect concerns the code optimization using GPGPU programming and message passing interface (MPI) techniques to significantly reduce computational time and cost, see, e.g., [13,38,44]. This step will allow three-dimensional modelling as well as shape and material optimization, supporting applications concerning realistic designs.…”

“…This step will allow three-dimensional modelling as well as shape and material optimization, supporting applications concerning realistic designs. Finally, the present method could also find useful application to calculate the flexibility effects on the performance of novel marine renewable energy devices based on oscillating foils; see [13].…”

“…Devices based on flapping foils have also been studied as auxiliary thrusters augmenting the overall ship propulsion in waves, see, e.g., the works [5][6][7][8][9] and project BIO-PROPSHIP [10]. Moreover, oscillating foils are studied for the development of hydrokinetic energy devices, see, e.g., [11][12][13] or hybrid devices with enhanced performance exploiting combined wave and tidal energy resources, see [14].…”

Hydrodynamics of Biomimetic Marine Propulsion and Trends in Computational Simulations

“…Most of the investigations found in the literature are inspired by boxfish [83][84][85][86]. Other authors employed flapping foils for oscillating marine propulsors [87][88][89][90][91][92][93][94][95][96][97][98][99][100][101].…”

Numerical Study of an Oscillating-Wing Wingmill for Ocean Current Energy Harvesting: Fluid-Solid-Body Interaction with Feedback Control

“…The reader may not confuse the term "Active Control", which is widely used in the literature with "Feedback Control". Other research groups [18][19][20][21] have implemented simulations of actively controlled foils; however, their control schemes are actually openloop.…”