Abstract
With the growing global demand for clean energy, tidal current energy has gained attention as a sustainable power source. Compared to conventional turbines, the counter-rotating horizontal axis tidal turbine demonstrates marked advantages in tidal current energy extraction due to its superior power generation efficiency and reduced environmental disturbance. This study numerically examines flow characteristics in its wake, revealing through single/counter-rotating impeller comparison that rear impeller installation enhances output power, with predictive capability validated against experimental data. A thorough examination of the pressure, streamline, and velocity distributions for both the single and counter-rotating impeller configurations reveals a consistent pattern of wake expansion. Subsequently, a quantitative assessment of the wake velocity distribution under four distinct operational speeds of 200 rpm, 600 rpm, 1200 rpm, and 1800 rpm is undertaken specifically for the counter-rotating impeller. The findings indicate that the rear impeller consistently exhibits a favorable effect on the improvement of velocity losses and the reduction of the rotational wake's intensity, exhibiting superior adaptability under variable working conditions. These findings are of great significance for understanding the energy conversion mechanism and working characteristics of counter-rotating impellers, providing guidance for subsequent structural design and optimization practices.