A multiple Oscillating Water Column (OWC) device may provide better wave absorption over a wider frequency bandwidth than a single-chamber OWC due to multiple resonances. The scattering and radiation of three-dimensional oblique waves by an array of periodic dual-chamber OWCs are considered here along a coastal cliff. A semi-analytical model was developed based on potential flow theory and matching eigenfunction method to investigate the oblique wave interaction with a dual-chamber OWC array system. The velocity singularity at the tip of a chamber wall is resolved by introducing the Galerkin technique to accelerate the convergence. The semi-analytical solution is verified by the Haskind relation and energy conservation law. Hydrodynamics of the proposed system and the influence of wave and geometric parameters were investigated. Theoretical results indicate that a dual-chamber OWC array has a broader capture bandwidth than a single-chamber OWC array for both normal and oblique waves. The presence of the along-shore and cross-shore sloshing resonance is theoretically confirmed in each subchamber of OWC unit, which decreases the hydrodynamic efficiency and increases the wave reflection drastically. Although the wave loading on the chamber wall decreases with increasing incident wave angle θ, the wave loading on chamber/partition wall may increase sharply due to sloshing resonance at critical frequency kc. To our knowledge, this is the first attempt to investigate the hydrodynamics of dual-chamber OWC array under oblique waves. The present theoretical results indicate the potential risks of structural damage and total wave reflection due to sloshing resonance, which should be an important design consideration.

The wake characteristics of tidal turbines are significantly influenced by turbulence intensity (TI) and flow velocity in the marine environment. This study employs the Blade Element Momentum (BEM) -CFD method to model two-bladed horizontal tidal turbine wakes, simplifying the turbine geometry while ensuring computational efficiency. The numerical model, validated against experimental data, demonstrates reliable accuracy. Simulations were conducted for background TI levels of 2%, 6%, 10%, 14%, and 18%. Results indicate that wake regions initially expand and then contract, with the contraction point moving closer to the turbine as TI increases. At 2% TI, the wake influence region extends to an axial distance/diameter (X/D) ratio of 20, while at 18% TI, contraction begins at X/D = 4. Low TI results in more extensive low-speed regions, whereas high TI accelerates wake recovery. As TI increases, the wake's turbulence rapidly blends with the background, leading to a reduction in turbulence increments within the wake. Additionally, an analytical wake model for tidal turbines was developed, incorporating turbulence intensity into the formula. The predicted curve exhibited good agreement with the CFD data. This model enables a quick and efficient prediction of wake velocity changes under varying turbulence intensities.

The wake characteristics of tidal turbines are significantly influenced by turbulence intensity (TI) and flow velocity in the marine environment. This study employs the Blade Element Momentum (BEM)–CFD method to model two-bladed horizontal tidal turbine wakes, simplifying the turbine geometry while ensuring computational efficiency. The numerical model, validated against experimental data, demonstrates reliable accuracy. Simulations were conducted for background TI levels of 2%, 6%, 10%, 14%, and 18%. Results indicate that wake regions initially expand and then contract, with the contraction point moving closer to the turbine as TI increases. At 2% TI, the wake influence region extends to an axial distance/diameter (X/D) ratio of 20, while at 18% TI, contraction begins at X/D = 4. Low TI results in more extensive low-speed regions, whereas high TI accelerates wake recovery. As TI increases, the wake’s turbulence rapidly blends with the background, leading to a reduction in turbulence increments within the wake. Additionally, an analytical wake model for tidal turbines was developed, incorporating turbulence intensity into the formula. The predicted curve exhibited good agreement with the CFD data. This model enables a quick and efficient prediction of wake velocity changes under varying turbulence intensities.