Preliminary Evaluation of Drag Reduction Performance for Functional Surfaces with 60-degree Riblets Subjected to Taylor-Couette Flows

This study outlines the initial development of a drag-reducing surface with a 60 triangular riblet-groove design.The research covers the design, microfabrication, and performance evaluation phases.The riblet-groove surface, designed with a lateral spacing of 57.8 m and a depth of 50 m, was based on optimized parameters from literature.Two acrylic drums were fabricated using high precision multi-axis single-point diamond turning technology, achieving excellent surface quality and form accuracy (< 2 m).One drum had a flat surface, while the other featured the riblet-groove design.The functional performance was evaluated using a rheometer-based Taylor-Couette system, which recorded torque, angular position, and normal force synchronously and simultaneously in time domain.At high angular velocities, air naturally incorporated into the Taylor vortices, leading to an unexpected drag reduction of 39.7%, likely due to air bubbles trapped in the riblet valleys acting as a lubricant.Before air inclusion, the maximum drag reduction observed was 7.1%.Further research is needed to understand this significant improvement in drag reduction and explore its potential applications in aerospace, automotive, marine, energy, and biomedical industries.