A lattice Boltzmann method for floating oscillating water column WECs

Abstract

In this study, a hierarchical multi-fidelity modelling framework, combining the lattice Boltzmann method (LBM) and potential-flow approach, is developed to investigate the two-dimensional floating oscillating water column (OWC) wave energy converters (WEC). The framework is built on a potential-flow model using the matching eigenfunction expansions, enabling efficient parametric screening and preliminary optimization, and then refined through viscous-flow LBM simulations to obtain more physically realistic estimations of hydrodynamic efficiency and motion responses. Numerically, this LBM based modelling framework incorporates a single-phase volume-of-fluid (VOF) method for capturing air-water interface and employs an interpolated bounce back- Galilean-invariant momentum exchange method (IBB-GIMEM) for handling air-water-solid interactions. Wave generation and absorption are realized through a momentum source technique and a perfectly matched layer (PML), respectively. Furthermore, a pneumatic model accounting for air compressibility is two-way coupled with this hydrodynamic model to evaluate the pressure response within the OWC chamber. Validation against experimental measurements confirms that the proposed modelling framework reliably captures both the hydrodynamic motions and the pneumatic dynamics. This framework is subsequently utilized to study the power extraction performance of an elastically constrained heave-only OWC WEC. Results highlight the effectiveness of this staged modelling strategy in providing a computationally efficient yet physically detailed analysis of floating OWC-wave interactions, supporting its application in the design and optimization of wave energy systems.