Vortex Configuration behind Flapping Wings

In avian flight, different stroke mechanism can be observed providing maximal lift and minimal drag. The corresponding high beat frequencies and flow velocities lead to unsteady and turbulent flow conditions and, thus, to complicate numerical and experimental studies of avian flight in terms of vortex shedding, wake configuration or pressure development. Approximating the wing motion by a sinusoidal wing rotation about two axes, a numerical and experimental avian model has been developed at the Institute for Fluid Mechanics at the Karlsruhe Institute of Technology (KIT), Germany. Numerical simulation techniques of fluid-structure-interaction (FSI) were used to capture the unsteady aerodynamics of the flapping wings. Complex vortex chains consisting of closed ring vortex structures behind each wing interlocked crosswise have been identified for all investigated flow conditions.