Direct Numerical Simulation of Seal Whisker Dynamics in Upstream Wakes

Harbor seals use their uniquely shaped whiskers to detect and track vortices generated by moving objects in water. In this sensory process, the vortices generated by the seals themselves are considered noise, while the wake from upstream objects is treated as the signal. Two different types of studies help to elucidate the behavior of these undulated whiskers. The first is vortex-induced vibration (VIV), which examines how whiskers respond to vortices generated by their own motion. Results show that seal whiskers suppress the formation of their own vortices, resulting in significantly smaller vibrations compared to conventional geometries such as cylinders. The second type, wake-induced vibration (WIV), investigates the response of a whisker placed in the wake of an upstream object. This is carried out in the current research using direct numerical simulation (DNS) on a real whisker segment. Simulations explore different upstream cylinder sizes in both staggered and tandem arrangements and analyze fluid–structure interaction. The results reveal that whiskers perform a slaloming motion through the wake, effectively capturing the frequency and size of the upstream object’s wake. A force partitioning method is also applied to separate the total pressure force on the whisker into components: added mass, vortex-induced, and viscous diffusion forces. This decomposition highlights the critical role of upstream vortices in driving whisker vibrations. Overall, this research demonstrates how seal whiskers amplify upstream wake signals while suppressing self-induced noise, offering insights into their remarkable sensing capabilities.