Multiple Modes of Filament Flapping in a Uniform Flow

The instability of a flexible filament immersed in uniform flow is studied. A numerical simulation based on the immersed boundary method is conducted on a two-dimensional uniform flow past a flapping filament. Different from the conventional bistability behavior, more regions of initial states of filament corresponding to different modes of motion are partitioned at each freestream velocity, and a new stable mode of motion with smaller flapping amplitude is observed. Mode selection highly depends on these initial states.