Turbulent drag reduction via adaptive surface curvature determined by flexible structural deformation

Turbulent boundary layers critically influence energy consumption and performance in ships. Conventional active drag reduction methods can achieve significant resistance reduction but require high energy input and are difficult to implement at large scales, while passive techniques such as microstructured surfaces or polymer additives exhibit limited effectiveness, poor durability, and restricted environmental compatibility under practical operating conditions. Inspired by biological surfaces, this study investigates drag reduction using an adaptively deforming flexible plate in high-Reynolds-number turbulent flow. A shape-based approach is adopted: the deformation that minimizes instantaneous pressure drag and total drag is determined via two-way fluid–solid interaction and then fixed to isolate geometric effects. Since the extracted geometry corresponds to simultaneous minima of pressure drag and total drag, the fixed surface modifies the near-wall velocity gradient and wall shear, thereby reducing the frictional contribution to the total drag while maintaining pressure drag within a controllable range. These coordinated effects reorganize near-wall turbulence structures and ultimately lead to a net reduction in overall drag. These modifications reorganize near-wall turbulence structures and lead to a net reduction in wall shear stress. The results provide quantitative insights into turbulent drag reduction mechanisms and offer conceptual guidance for the development of passive surface strategies in high-Reynolds-number flows.