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In order to effectively utilize the tidal current energy in offshore wind farms, a swing oscillating hydrofoil system for tidal current energy capture is proposed. The system is constructed with oscillating hydrofoils as tidal current energy capture device combined with offshore wind turbine underwater tower. Lattice Boltzmann method and large eddy simulation method were combined, and the hydrodynamic characteristics and energy collection efficiency of a NACA0015 airfoil with different motion parameters were numerically analyzed with or without the influence of tower wake. The influence of pitch amplitude, heave amplitude and chord length of the hydrofoil on the energy collection efficiency of the system is analyzed from the aspect of vortex structure in the moving process. The results show that the energy collection efficiency of the oscillating wing is significantly improved by the trailing vortex of the tower, and the vortex shedding behind the tower can reduced by the addition of the oscillating wing, consequently, the fatigue load caused by the flow around the cylindrical body can be reduced. The energy capture efficiency of the oscillating wing can reach a highest efficiently of 30.72% in the wake vortex region of the tower, which has obvious advantages compared with the traditional oscillating wing tidal current energy capture device, and provides an effective way to improve the overall energy utilization rate of offshore wind farms.

Airfoil is a key factor that influences the hydrodynamic performance of vertical axis tidal current energy turbine. In order to explore the influences from the runner’s blade airfoil towards its hydrodynamic performance, three-dimensional unsteady flow numerical simulation on four airfoils of straight blade H type of tidal current energy turbines was carried out, under the precondition of same turbine compactness. Through investigating the influences from the four different airfoils of H blade towards the runner in terms of its dynamic torque feature and hydropower utilization coefficient, this research has analyzed the hydrodynamic performance of the tidal current energy turbine. As the research result indicates, the maximum dynamic torque value of the single-blade turbine with NACA0015 airfoil is significantly higher than that of the other three airfoils; while the maximum value of the overall runner torque is determined by the operating conditions such as different stream speed etc. As a whole, hydropower utilization coefficient of the turbine with asymmetric airfoil NACA4415 is better than that of the other three airfoils. This research has provided references for the design and airfoil selection for the new type of tidal current energy turbine.