Influence of multi-chambers and buoy configuration on the hydrodynamic performance of a bottom-detached OWC-breakwater

• The energy balance method well-predicts the hydrodynamic performance OWC-breakwater models with varying number of chambers and buoy configuration. • The model with two OWC chambers and an attached buoy has the highest energy extraction. • The model with three OWC chambers and an attached buoy has the lowest energy transmission. • An increase of 1.5 times in peak value and 0.6 times in average of energy extraction from reference model is observed. • The level of energy loss has minimal correlation with the levels of energy extraction and transmission. An oscillating water column (OWC)-breakwater device could serve a dual function of generating sustainable wave energy, as well as protecting coastal infrastructure from the constant impact of ocean waves. This dual application feature could potentially be enhanced with the additions of multi-OWC chambers and buoys. This configuration optimisation is investigated in the present study, where five models of the OWC of varying number of chambers and configuration of buoy are tested for their wave energy extraction and transmission. The numerical study uses Ansys FLUENT, a computational fluid dynamics solver, which uses Reynolds Averaged Navier Stokes equations to solve the motion of fluid flow. Volume of Fluid model is used to track the interphase between air and water phases. Energy balance method is used to analyse the performance of the OWC, with some novel equations derived in accordance to the configuration of the models. Results showed that the model with two chambers and an attached buoy has the highest peak and average extracted energy, with an improvement of 177 % and 153 % respectively, compared to the reference model of a standalone OWC. Meanwhile, the lowest peak(s) and average transmitted energy, with a reduction of 43 % and 30 % respectively, compared to the reference model, was found for the model with three chambers and an attached buoy. These significant improvements are valuable for further investigations. Additionally, the inclusion of an attached buoy and an optimal number of two chambers were found to improve the energy extraction of the OWC.