Numerical Study of Mechanisms of the Vortex Formation in the Wake of Dual-Flapping Foils

Abstract

The vortex formation and organization are the key to understand the intrinsic mechanism in flying and swimming in nature. The vortex wake of dualflapping foils is numerically investigated using the immersed boundary method. Beside the deflection of the reversed von-Kármán vortex street, an interesting phenomenon, the deflection of the von-Kármán vortex street, is observed behind the dual-flapping foils. The deflected direction is not according to the initial direction of biplane's flapping motion. And the deflection angle is related to the difference between upward and downward deflecting velocities.