Experimental Study of Flow-Induced Oscillations of a Flexible Symmetric Hydrofoil

Flow-induced oscillations of a flexible symmetric hydrofoil with a NACA 0021 cross section are studied experimentally for a range of flow velocities and angles of attack. The hydrofoil is made of silicone rubber with a chord length of C = 2 cm and length of L = 34.7 cm, corresponding to an aspect ratio of AR = 17. Experiments are conducted in a recirculating water tunnel whereby displacement of the hydrofoil at discrete points along its length are recorded using a Panasonic DMC-FZ200 camera in the crossflow direction and Phantom Miro M110 high speed camera in the inline direction. Displacement is then quantified using Adobe After Effects tracking software. Vortex-induced vibration is observed to occur whereby the largest amplitudes of oscillations occur when the chord length of the hydrofoil is placed perpendicular to the direction of the flow, α = 90°. Performed simultaneously with the displacement measurements, hydrogen bubble flow visualization reveal the vortex shedding patterns observed in the wake of the hydrofoil.