Vibrissa-inspired geometries exhibit enhanced sensitivity to wake-induced vibrations

We report on experiments designed to characterize the wake-induced vibration (WIV) experienced by bluff bodies immersed in unsteady flows. A sinusoidally pitching and heaving hydrofoil upstream is used to generate vortices of different strength and frequency which advect downstream and impinge on a bluff body that is free to oscillate in the flow. Using a real-time Cyber-Physical System (CPS) we systematically prescribe the virtual mass, spring constant, and damping of the elastically mounted models. We characterize the forces and displacements of the WIV response of (i) a circular cylinder, (ii) an elliptical cylinder and (iii) a seal whisker inspired vibrissa model with an undulating elliptical geometry. We find that the reduced aspect ratio objects, known to suppress vortex-induced vibrations (VIV) in a clean flow, experience WIV with the highest amplitude oscillations occurring when the structural frequency of the test object matches the frequency of the upstream foil. Further, the vibrissa has a lower damping ratio than the elliptical cylinder, suggesting that the vibrissa geometry may serve as a high sensitivity flow disturbance sensor.