SPH-integrated chamber model applied to floating OWC devices: 2-D and 3-D analysis

In this work, we present the implementation and validation of an analytical chamber model, coupled to a single-phase Smoothed Particle Hydrodynamics (SPH) approach, to mimic the pneumatic power take-off (PTO) characterizing an Oscillating Water Column (OWC) wave energy converter. The power extraction mechanism of OWCs relies on the compression and decompression of an air pocket placed above a water column within the device chamber, which oscillates due to the incoming waves. A reliable PTO modeling is crucial in order to estimate and optimize the energy conversion performance of this kind of WECs. Usually, the pneumatic PTO is simulated via two-phase mesh-based techniques, which are quite effective when dealing with fixed OWCs. Whereas, meshless methods like SPH have proven their feasibility in modeling floating devices and free surface flows, but are less efficient when two phases (air and water) are involved, due to their higher computational cost. Hereby, instead, an alternative procedure that envisions the integration of an analytical chamber model within a single-phase SPH approach is carried out and implemented in the open source code DualSPHysics. In this paper, such a methodology is adopted and validated, against experiments, while replicating the behavior of a 2-D floating OWC and it is then employed to estimate the response of a 3-D floating OWC. A numerical power output study for the latter configuration is provided as well. To the authors knowledge, this work represents the first attempt at modeling the pneumatic PTO of floating OWC devices through an SPH technique.