Abstract
Wave induced motions due to actual sea state conditions will impact the performance of floating horizontal axis tidal turbine systems. This paper presents the results from numerical simulations of a 3-bladed horizontal axis tidal turbine oscillating in surge motion in a moving reference frame. The optimum tip-speed ratio, λ = 4.4 and k-ω SST turbulence model were used in the present study. The Navier-Stokes equation was modified by adding an inertial term to the equation and the Dirichlet boundary condition was also modified in order to simulate in the moving reference frame. The surge oscillations were parameterised in terms of the ratio of surge amplitude to rotor radius, A*, and the ratio of oscillation frequency to the rotational frequency of the rotor, ω*. A series of tests were conducted to study the effect of each parameter on the hydrodynamic performance of the tidal turbine. The results show that stall can occur on the blade when the velocity relative to the rotor is sufficiently high. In certain cases, negative thrust and power coefficients were observed when the velocity relative to the rotor is low. The fluctuation in blade loading increases together with the amplitude and frequency of oscillation, which will contribute to the fatigue of the rotor.
Highlights
THE demand for energy increases every year with the continued growth of economies around the world
The present study focuses on the hydrodynamic performance of a turbine oscillating in surge motion
The present study investigates the hydrodynamic performance of a turbine oscillating in surge motion
Summary
THE demand for energy increases every year with the continued growth of economies around the world. Floating tidal turbines may be more suitable for deep water (depth >30 m) operations rather than shallow water, as the flow speed in a channel is highest near the Manuscript received 16 March; accepted 26 March; published 8 Sept, 2020. References [1], [2], [3] investigated the hydrodynamic performance of a tidal turbine in yaw, surge, and roll motions, respectively. These studies used computational fluid dynamics (CFD) models to simulate the floating tidal turbine. The present study uses the moving reference frame method to reduce the computational cost and maintain mesh quality, in comparison to the mesh morphing methods used in previous studies
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