Numerical Study on the Vibratory Response of Undulatory Seal Whiskers to Wakes*

Harbor seals utilize their uniquely shaped whiskers, which have evolved as extraordinary hydrodynamic sensors, to track vortex wakes left by moving animals. Behavioral experiments have demonstrated seals' remarkable ability to differentiate and follow upstream wakes using these whiskers. Fundamental experiments revealed that the geometry of seal whiskers, when placed in the wake of a circular cylinder, generates stronger vibratory responses and better frequency synchronization compared to simple circular and elliptical cylinders. This study conducts a parametric analysis of the wake-induced vibration (WIV) of a whisker using direct numerical simulation (DNS). One segment of the whisker is modeled as an elastically mounted rigid body with periodic boundary conditions. The whisker is positioned downstream of a cylinder, with WIV analyzed in both tandem and staggered arrangements. Key parameters such as reduced velocity and cylinder relative size are also examined. Preliminary results indicate a slaloming motion, consistent with previous experimental findings. This study focuses on two mechanisms of WIV—wake stiffness-induced vibration and vortex force-induced vibration—and compares their effects on the whiskers' vibratory response. These comparisons elucidate the dominant factors contributing to WIV and enhance our understanding of how whisker geometry influences wake response.