The effects of roll motion of the floating platform on hydrodynamics performance of horizontal-axis tidal current turbine

Abstract

Under the condition of actual sea state, hydrodynamic characteristics of floating horizontal-axis turbine are related to wave characteristics and floating carrier motion responses. We recently published the hydrodynamic performance and axial damping coefficient of the horizontal-axis tidal current turbine influenced by surge motion in constant inflow using CFD simulation (Zhang et al. Renew Energy 74:796–802, 2015). Encouraged by this result, this paper uses sliding mesh to analyze the hydrodynamic characteristics in uniform stream when the turbine is forced to roll and studies influences of different roll frequency, roll amplitude, and tip speed ratio on turbine’s performance. Roll-damping coefficient and added mass coefficient can be derived by torque almanacs curve of rolling turbine by the least square method. Results show that the turbine axial load, roll moment, and energy utilization ratio will fluctuate in roll motion; the more roll frequency and roll amplitude, and the more load and moment wave amplitude of momentary value. The crest value occurs in the balance position of rolling, while the amplitude of oscillation depends on the angular speed of rolling and rotating speed of the turbine. The frequency and amplitude of the roll have little impact on damping coefficient, but rotational speed of the turbine has positive impact on this coefficient. Results of this study can provide data to study motion response of floating carrier for floating tidal current turbine system and check the structural design and control of the electric output.