Hydrodynamic performance of a penguin wing: Effect of feathering and flapping

The penguin is the fastest underwater swimmer among wing-propelled diving birds. To figure out mechanism for its excellent swimming, hydrodynamic performance of a wing numerically investigated using an immersed boundary method with incompressible flow solver. This study examines effects feathering, flapping, and Strouhal number (St) under preset motion. Results indicate that feathering primary contributor to thrust generation. change in angle attack (AoA) can qualitatively reflect lift but not thrust. Therefore, new variable, (AoT, αT), introduced effectively across different kinematic parameters. Optimal amplitude balances decrease AoA increase achieve highest AoT Excessive degrades leading-edge vortex shear layers, transforms pressure side suction side, ultimately causes negative (drag). Spatial analysis shows outer three-fifths are source thrust, contributing 85.4% generation at optimal amplitude. Flapping has little impact on increases linearly St scope examination, leading larger lower swimming efficiency. Thus, dimensionless number, Stm, describe work provides insights into propulsion aquatic swimmers flapping–feathering wings helps design novel bio-inspired vehicles.