Implementation of a single-phase SPH pneumatic power take-off model for small- and full-scale OWC devices within DualSPHysics

A versatile single-phase implementation to model the pneumatic power take-off (PTO) of fixed and floating oscillating water column (OWC) devices is proposed within the Lagrangian software DualSPHysics. The OWCs’ PTO converts wave energy into electricity, exploiting the compression and decompression of air trapped inside the device chamber. The numerical modeling of such a physical phenomenon is a crucial aspect in guaranteeing accuracy in energy conversion performance estimations, especially at full scale. It is, however, a challenging task in meshless environments like Smoothed Particle Hydrodynamics (SPH), adopted herein. Proper physical representation in single-phase models, or high computational effort in multi-phase approaches, indeed, limit the application of SPH to date. In this work, it is developed a mono-phase SPH model coupled with an analytical chamber model, which adequately describes the air pressure variation inside the chamber without sharpening the computational cost, allowing for inclusion of air compressibility effects. This implementation is validated against experimental results concerning fixed OWCs, and is employed to investigate the behavior of the same devices at full scale, confirming the relevance of air compressibility in the latter case, as assessed by consolidated mesh-based findings. Moreover, both the compressible and incompressible pneumatic formulations of the proposed method are validated against laboratory tests over a heaving OWC, constituting one of the first investigations that takes into account air compressibility when studying a floating OWC device. In addition, hydrodynamics studies are performed and presented to visualize the flow behavior near the devices of interest.