Wavy Whiskers in Wakes: Explaining the Trail‐Tracking Capabilities of Whisker Arrays on Seal Muzzles

Abstract

Seals can detect prey up to 180 m away using only their flow‐sensing whiskers. The unique undulating morphology of Phocid seal whiskers reduces vortex‐induced vibrations (VIVs), rendering seals highly sensitive to biologically relevant flow stimuli. In this work, digital models of harbor and grey seal whiskers are extracted using 3D scanning and a mathematical framework that accurately recreates their undulating geometry is proposed. Through fluid–structure interaction studies and experimental investigations involving a whisker array mounted on 3D‐printed microelectromechanical systems sensors, the vibration characteristics of the whisker array and the interaction between neighboring whiskers in steady flows and fish‐wake‐like vortices are explained for the first time. Results reveal that the downstream vortices intensity and resulting VIVs are consistently lower for grey than harbor seal whiskers and a smooth cylinder, suggesting that the grey seal whisker geometry can be an ideal template for the biomimetic design of VIV‐resistant underwater structures. In addition, neighboring whiskers in an array influence one another by resulting in greater flow vorticity fluctuation and distribution area, thus causing increased vibrations than an isolated whisker, which indicates the possibility of a signal‐strengthening effect in whisker arrays.

Morphological Intelligence Mechanisms in Biological and Biomimetic Flow Sensing

“…The C D and C L showed a significant drop when A C increased from 0.1 to 0.2 and there was no significant change when A C increased from 0.2 to 0.3 This suggests that oscillation lift and drag reduction can be achieved by controlling the geometric parameters of the whisker‐inspired model, but there may be a limiting threshold value for A C and A T . Zheng et al [ 86 ] compared the VIVs of two types of seal whiskers (harbor seal and gray seal) and a smooth cylinder, and found that the vortex intensity of the smooth cylinder was significantly higher than that of the two types of seal whiskers, which suggested that the seal whiskers had a VIV suppression effect. Meanwhile, the vortex intensity of the harbor seal whiskers was higher than that of the gray seal whiskers because the geometry of the gray seal whiskers had a better ability to suppress the VIV.…”

Structured carbon nanotube–elastomer nanocomposites with a morphing–contact mechanism for an advanced underwater perception warning system

“…24 Marine organisms have the capabilities of sensitive perception, danger capturing and further self-protection. [25][26][27] While recent reports have focused on contact-based and contactless underwater sensing functions, the capability of signalling danger is urgently desired. More recently, Lai et al reported a series of novel wearable underwater sensing and rescue devices (e.g., superhydrophobic knitted fabric, 28 flexible MXene-based hydrogels, 29 etc.)…”

Undulating Seal Whiskers Evolved Optimal Wavelength‐to‐Diameter Ratio for Efficient Reduction in Vortex‐Induced Vibrations

“…Unlike the well‐studied fish lateral line system mentioned earlier, the understanding of the seal whisker sensing system is relatively nascent and has thus been the focus of multidisciplinary studies over the past decade, [ 13 ] with a particular emphasis on the effect of undulations in the whisker morphology on VIV suppression. [ 14 , 15 , 16 , 17 ] Due to the twin difficulties of limited access to seal whiskers and performing vibration and fluid flow measurements at the small scale of the seal whisker (cross‐sectional dimensions < 1 mm), several researchers also used approaches such as physical modeling (e.g., by performing experiments on scaled‐up whisker‐like structures [ 12 , 18 , 19 , 20 ] ) and numerical modeling [ 21 , 22 , 23 , 24 , 25 ] to study the effect of undulations on VIV. The insights gleaned from these studies can be valuable in realizing bioinspired engineering applications such as underwater flow sensing, [ 26 ] biomimetic wind turbine designs with drag force reduction, [ 27 ] and vibration‐reducing cables in offshore structures.…”