Undulatory swimming on a free surface

A wide variety of swimmers in nature use body undulations to generate a propulsive force, in part owing to the relative insensitivity of the principle of undulatory swimming to the value of the Reynolds number $Re=UL/\nu$, which measures the relative importance of viscous and inertial forces in the flow considered ($U$ and $L$ being the typical speed and length of the animal, and $\nu$ the kinematic viscosity of the surrounding fluid). Here we study a flexible filament forced to oscillate by imposing a harmonic motion to one of its extremities (using magnetic interactions) and propelling itself at the surface of a water tank. This experiment serves as a canonical model for studying the interactions between an elastic structure undergoing complex deformations and the surrounding fluid.