Effects of vortex generator on the hydrodynamic characteristics of hydrofoil and horizontal axis tidal turbine

Abstract

Tidal turbine blades are prone to flow separation in the boundary layer under high speed or high angle of attack, which will reduce energy efficiency and even the stall damage of the blades. This paper proposes introducing the flow control theory of vortex generators (VGs) to tidal turbines and studying the influence of VGs on the hydrodynamic characteristics of the tidal turbine blades. First, a numerical study is performed to investigate the effects of VGS on the hydrodynamic performance of the National Advisory Committee for Aeronautics (NACA) 4418 hydrofoil. The impact of different parameters, such as VG arrangement, spacing, height, and length, on the hydrodynamic performance of hydrofoil is studied by the computational fluid dynamics method. The results show that VGs can effectively suppress the flow separation and improve the maximum lift coefficient of the hydrofoil. The influence of VGs on flow separation characteristics of horizontal axis tidal turbines is studied by the CFD method. The results show that the flow separation of turbine blades mainly occurs at the root part of the suction surface, and the flow separation region expands radially as the flow velocity increases. VGs can effectively reduce the flow separation area on the suction side of turbine blades by suppressing the flow separation effect. Compared with the turbine blades without VGs, the power coefficient of turbine blades with VGs is increased by up to 5%. The flume experiment verifies the accuracy of the simulation results.