Abstract
Abstract Simulation of the hydrodynamic performance of a floating current turbine in a combined wave and flow environment is important. In this paper, ANSYS-CFX software is used to analyse the hydrodynamic performance of a vertical-axis turbine with various influence factors such as tip speed ratio, pitching frequency and amplitude. Time-varying curves for thrust and lateral forces are fitted with the least squares method; the added mass and damping coefficients are refined to analyse the influence of the former factors. The simulation results demonstrate that, compared with non-pitching and rotating turbines under constant inflow, the time-varying load of rotating turbines with pitching exhibits an additional fluctuation. The pitching motion of the turbine has a positive effect on the power output. The fluctuation amplitudes of thrust and lateral force envelope curves have a positive correlation with the frequency and amplitude of the pitching motion and tip speed ratio, which is harmful to the turbine’s structural strength. The mean values of the forces are slightly affected by pitching frequencies and amplitudes, but positively proportional to the tip speed ratio of the turbine. Based upon the least squares method, the thrust and lateral force coefficients can be divided into three components, uniform load coefficient, added mass and damping coefficients, the middle one being significantly smaller than the other two. Damping force plays a more important role in the fluctuation of loads induced by pitching motion. These results can facilitate study of the motion response of floating vertical-axis tidal current turbine systems in waves.
Highlights
Traditional fossil fuels account for a major part of the world’s energy consumption, but we will no longer use fossil fuels in the few years, according to the current mining rates [17]
An additional fluctuation to that induced by turbine rotation itself is observed in the thrust and lateral forces of the turbine
We study the hydrodynamic performance of vertical-axis tidal current turbines under pitching motion with different speed ratios, pitching frequencies and amplitudes
Summary
Traditional fossil fuels account for a major part of the world’s energy consumption, but we will no longer use fossil fuels in the few years, according to the current mining rates [17]. In 2011, Li [10] conducted a series of experiments with vertical-axis turbines to research the hydrodynamic influence of density, leaf number, pitch angle and chord length, and compared the results with those from a numerical simulation to validate the reliability of CFD. It showed that the SST turbulence model can provide higher computational accuracy, and the grid has little influence when Y+ ≤ 2. Studying VAWT in tilted flow conditions can provide constructive comments on the research on tidal current turbines rotating around a skewed axis. CFX, CFY and CP are essential indices for assessing the hydrodynamic performance of a turbine
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