Vortex dynamics and fin-fin interactions resulting in performance enhancement in fish-like propulsion

The generation of leading-edge vortices (LEV) by the caudal fin (CF) has long been recognized as playing a key role in efficient propulsion in fish-like swimming. This study focuses on LEV enhancement due to vortex shedding of the median anal fin (AF), utilizing trout's unique morphology and fin configurations. The shed anal-fin vortex (AFV) is found to stabilize and strengthen the LEV of the CF through its shearing with the CF leading edge, creating stronger leading-edge suction, resulting in stronger thrust production and increased propulsive efficiency in trout-like swimming.