Fluid damping, added mass, and vorticity-induced forces influence sensitivity to vibration of vibrissa-inspired models

We report on experiments designed to characterize how span-wise undulations in an elliptical cylinder model, inspired by the geometry of seal whiskers, affect wake induced vibration (WIV). Previous work has shown that low aspect ratio objects suppress vortex-induced vibrations (VIV) while amplifying wake-induced vibrations (WIV), regardless of body undulation. Using a real-time Cyber-Physical System (CPS) we conduct ringdown experiments at a range of structural frequencies by systematically prescribing the virtual mass, spring constant, and damping of the elastically mounted models. We find that across all test frequencies, both the damping ratio and fluid damping of the elliptical cylinder is greater than the vibrissa, allowing the vibrissa to exhibit a higher signal-to-noise ratio. We employ both 2D and 3D force/moment partitioning methods (FMPM) on velocity field measured using volumetric particle image velocimetry (PIV). The force contributions arising from (i) the added mass due to the body kinematics and (ii) the vortical flow structures shed from the body have the most significant contributions to the force measurements observed. FMPM also provides insight into which flow structures are imparting what force components on the body, and the differences between the the elliptical cylinder and the undulating vibrissa geometry.