Numerical study of asymmetric effect on a pitching foil

This study investigates numerically the effect of asymmetric sinusoidal oscillating motion on the propulsion performance of a pitching foil and attempts to gain insight in whether the low thrust generated by pure pitching could be improved by asymmetric motion. The propulsion performance and flow structure are explored by solving the unsteady Navier{Stokes equations. Computations are conducted for a range of oscillation frequency, pitching amplitude, and asymmetry. The results show that the higher asymmetry can induce the stronger reverse Von Karman vortex in the wake, which in turn leads to the increased thrust. However, the propulsion effciency reduces as increasing asymmetry. Computed results are further adopted to shed insight into the mechanism of thrust enhancement.