Vertical Axis Autorotation Current Turbine (VAACT) Analysis With Power Take-Off System

This research paper examines the effectiveness of the Vertical Axis Autorotation Current Turbine (VAACT) by conducting simulations using a two-dimensional Computational Fluid Dynamics (CFD) model. The verification and validation are carried out using the recommended practices from the International Towing Tank Conference (ITTC) [1]. The verification process includes checking the domain, grid, and time-step, and the model results are compared to tests at the Laboratory of Waves and Currents (LOC-COPPE/UFRJ) using an S-shaped VAACT profile. In the CFD environment, the power take-off (PTO) system is modeled by adding an external torque due to the PTO system and the damping coefficient (Kt) into a User-Defined Function (UDF). The validation is performed at Reynolds numbers ranging from 70,000 to 135,000. The time series analysis indicates that both lift and drag forces play a crucial role in the turbine’s performance. Although the instantaneous efficiency is in phase with the drag force, the lift is responsible for driving the device at smaller drag magnitudes. Additionally, the torque coefficient is in phase with the lift force, which implies that the hydrodynamic performance can be governed by it. The analysis also reveals that the returning blade adds a resisting torque on the turbine, which may impact its performance, as represented by high-pressure points at this blade.