Abstract
Wave energy harvesting beneath the ocean surface remains a virtually untapped potential. Sub-surface wave energy converters (WEC) minimize surface expression, enhancing survivability and reducing ship-WEC interactions. However their efficiency and dynamic behavior, unlike their surface counterparts, have yet to be thoroughly investigated. In this study, we examine the dynamics and PTO efficiency of sub-surface WECs, with varying submergence depths, across a range of incident wave conditions.
We employ a GPU-based, mesh-less CFD modeling framework that couples an open-source Smoothed Particle Hydrodynamics (SPH) model GPUSPH (www.beta.gpusph.org) with the open-source multi-physics simulation engine Project Chrono (www.projectchrono.org). The coupled modeling framework directly resolves the dynamics of complex multi-body WECs and the surrounding turbulent flow. SPH's Lagrangian formulation can efficiently resolve free surface flows and fluid-structure interaction without the complications of surface tracking and interpolation introduced by mesh-based CFD implementations such as OpenFOAM or Ansys Fluent models.
The model has been successfully used for studying various scientific and engineering problems involving nonlinear and breaking surface gravity waves. Here we validate the model against available laboratory data of single- and double-flap OSWECs interacting with regular waves, including data recently collected in the Hinsdale Wave Research Laboratory at the Oregon State University. We then explore the dynamic behavior and PTO efficiency of sub-surface OSWECs to inform design improvements such as optimizing flap size, shape, or submergence depth. The proposed GPU-based modeling framework represents a significant advancement in the CFD-informed design of WECs, enabling much more efficient computations compared to traditional CPU-based CFD models.