Swimming Fast Versus Swimming Efficiently

Fish-like swimming gaits that generate maximum thrust differ from those that achieve maximum efficiency. The focus of this study was to examine and compare the optimal gaits for fish-like swimming to attain maximum thrust and maximum efficiency. To identify these optimal swimming gaits, we developed and utilized an efficient adjoint-based optimization algorithm. This algorithm enabled us to identify periodic swimming gaits that maximize the time-averaged thrust or propulsive efficiency. Our investigation utilized a 2D oscillating plate as the propulsor in the Direct Numerical Simulation (DNS). Our analysis will compare the optimal swimming gaits for maximum thrust and maximum efficiency, elucidating their associated flow characteristics. Furthermore, we will incorporate the sensitivity information provided by the adjoint method.