Numerical Study on Liquid-Sealed Acceleration Rotor for Velocity Deficit Reduction Beneath Free Surface in a Circulating Water Channel

This study proposes and analyzes a surface flow acceleration rotor system to address the issue of non-uniform flow velocity beneath the free water surface. The system employs a liquid-sealed rotating rotor to induce shear flow, thereby enhancing local velocity distribution and improving flow uniformity. A three-dimensional numerical model was developed using STAR-CCM+, and simulations were conducted under varying rotor installation heights, rotor–casing gaps, and structural configurations. The optimized configuration (Hgap = 47mm, Dgap = 3mm) achieved the best velocity recovery, with a velocity of 0.97. Comparative analysis showed that polygonal-edged casing outperformed rectangular-edged ones by generating more concentrated shear layers, thus improving flow induction efficiency. Furthermore, water temperature variations within the 10–20˚C range were found to have negligible influence on velocity recovery. The results provide theoretical and practical guidance for flow field regulation near free surfaces in hydrodynamic experiments and demonstrate potential for engineering applications.