Utilization of Boundary Element Method (BEM) based on linear potential flow for modelling Oscillating Water Column (OWC) devices has gained popularity in the last two decades. The commercial BEM solver WAMIT has been used widely for modelling OWCs and validated using experimental modelling (Delauré et. al. 2003, Bingham et. al. 2015, Faÿ 2020). The open-source BEM solver NEMOH has however been mostly ineffective in modelling OWCs since the main approach adopted previously modelled the imaginary piston as a thin disk. In this research, the multi-body interaction problem has been adopted in modelling a box-type and bottom-detached OWC device in NEMOH, where the imaginary piston has been modelled to the length of the internal water column (Penalba et.al. 2017) and compared with experimental data. A further comparison is drawn with the numerical method of Computational Fluid Dynamics (CFD) , which has shown to be accurate for modelling OWC devices (Simonetti et. al. 2015), yet requires significantly higher computational resources than BEM. A two-dimensional CFD numerical wave tank, developed generating and absorbing waves with the waves2Foam toolbox (Jacobsen et al., 2012) of the open-source package OpenFOAM, is used for comparative purposes.@en

The Oscillating Water Column (OWC) wave energy converter has been shown to have high potential, thus rendering extensive development in recent years. In order to further accelerate its development, highly accurate yet computationally efficient tools are necessary particularly when studying the interaction of multiple OWC devices. This paper proposes a new framework for fixed OWC devices with an orifice, that uses the input from a high fidelity non-linear numerical model to improve the accuracy of a low fidelity linear numerical model keeping computational costs low. This is done by accounting for the non-linearities in the pressure-flow of an orifice in the input to the linear numerical model. Experimental data is used to validate the framework, thus providing an accurate and computationally efficient linear numerical model, that can be used for the preliminary analysis of fixed OWC devices.@en