Vortex Shedding behind a Seal Whisker and Vortex-Induced Vibration

Harbor seals can track their prey by detecting minute disturbance of the ambient water solely by their whiskers, instead of visual and auditory senses. The outstanding hydrodynamic capability of seals’ whiskers is attributed to the unique undulating three-dimensional morphology of the whisker. Research using whisker-like models show that the undulating morphology suppresses vortex-shedding in the wake and reduces vortex induced vibration (VIV), especially when the major axis of the whisker is aligned with inflow (angle of attack or AOA = 0°). However, few laboratory studies have been conducted to reveal the interaction between the wake flow and the real seal whisker, which has a natural variation in length and size as well as a twist along the length. This work uses high-speed particle imaging velocimetry (PIV) to analyze the vortex shedding generated by a real elephant seal whisker (undulating morphology) and compare it to that of a California sea lion (smooth morphology) at Reynolds number of 400. The vortex-induced vibration of the whiskers is also measured at two AOAs, 0° and 90°. The current work can provide insights on the effects of the inflow direction on the flow-whisker interaction, and development of high-performance whisker-inspired engineering components.