The hybrid form of wave energy converter (WEC) is a recent advancement in research concerning harvesting energy from the ocean. This study investigates the effect of size and position of the point absorber integrated with a backward bent duct buoy. The aim of this optimisation is to maximise the WEC-absorbed power and heave response amplitude operators (RAO) at a specific sea site. The optimisation process was applied based on the data collected over a one-year period about sea characteristics for a nearshore region of the Mantanani Island. We present a methodology for optimising the Hybrid BBDB-PA based on a statistical analysis and the hydrodynamics of the system in the frequency and time domain. We used the ANSYS/AQWA software for the hydrodynamic diffraction analysis, and the design of experiments method was applied through the statistical software to determine the optimised parameters. We found that the diameter and gap length between PA and BBDB were found to significantly influence two characteristics, namely, heave RAO and maximum power absorption of PA. This observation shows that the PA size was directly proportional to the performance because a higher diameter has more contact with the ocean’s wet surface area with the ocean and absorbed higher wave energy. Moreover, the gap length between the PA and BBDB was directly correlated with a wavelength, which followed the theoretical value for peak-to-trough length, where the maximum wave height occurs. Despite the condition parameter, we discovered that the WEC position and arrangement were responsible for the highest value of the power, regardless of the PA position used in the experiment. The results of this research provide recommendations for optimising the ocean energy harvesting in order to fully utilise ocean space for energy.

Oscillating water column wave energy converters require self-rectifying turbines capable of maintaining stable performance under bidirectional airflow. This study numerically investigates the aerodynamic performance and internal flow characteristics of an axial-flow impulse turbine using OpenFOAM under both uniform and reciprocating airflow conditions. Rotor motion was modeled using the Multiple Reference Frame approach, and the numerical model was validated against experimental data for one-way flow at an inlet velocity of 8.71 m s⁻¹ and rotational speeds ranging from 300 to 1300 rpm. The CFD results successfully reproduced the experimental efficiency trend, yielding a peak efficiency of η = 0.4269 at 700 rpm and ϕ ≈ 0.95, which closely aligns with the experimental peak efficiency of η = 0.4425. Validation metrics demonstrated a high degree of accuracy, with an RMSE of 0.0219, a mean absolute error of 0.0197, a maximum absolute error of 0.0399, a squared Pearson correlation coefficient of 0.826, and a peak-efficiency difference of 3.5%. Flow-field analysis revealed that low rotational speeds resulted in high outlet velocities and incomplete energy extraction, whereas excessive rotational speeds caused flow misalignment, downstream vortex formation, and additional aerodynamic losses. Under reciprocating flow conditions, characterized by a sinusoidal velocity amplitude of 8.71 m s⁻¹ and periods of 0.5–2.0 s at 700 rpm, both input and torque coefficients exhibited hysteresis, with the strongest loops observed at the shortest periods. Examinations of streamline, pressure, and velocity distributions indicated that residual flow during flow reversal alters the effective inlet direction in the subsequent half-cycle, resulting in flow memory and a phase-dependent turbine response. As the present computational domain excludes the OWC chamber, these findings characterize turbine-level aerodynamic performance rather than the complete system power coefficient.