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

Seals are well-known for their remarkable hydrodynamic trail-following capabilities made possible by undulating flow-sensing whiskers that enable the seals to detect fish swimming as far as 180 m away. In this work, the form-function relationship in the undulating whiskers of two different phocid seal species, viz. harbor and gray seals, is studied. The geometry and material properties of excised harbor and grey seal whiskers are systematically characterized using blue light 3D scanning, optical and scanning electron microscopy, and nanoindentation. The effect of the undulating geometry on the whiskers' vibration in uniform water flow is studied using both experimental (piezoelectric MEMS and 3D-printed piezoresistive sensors developed in-house) and numerical (finite element method) techniques. The results indicate that the dimensionless ratio of undulation wavelength to mean whisker diameter (lambda/Dm) in phocid seals may have evolved to be in the optimal range of 4.4-4.6, enabling an order-of-magnitude reduction in vortex-induced vibrations (compared to a similarly-shaped circular cylinder) and, consequently, an enhanced flow sensing capability with minimal self-induced noise. The results highlight the importance of the dimensionless lambda/Dm ratio in the biomimetic design of seal whisker-inspired vibration-resistant structures, such as marine risers and wake detection sensors for submarines. Phocid seal whiskers possess a unique undulating geometry that reduces vortex-induced vibrations (VIV) and helps the seal track its prey. In this work, the form-function relationships in harbor and grey seal whiskers are studied. The results indicate that the wavelength-to-mean diameter ratio (lambda/Dm) of the undulating whiskers may have evolved to possess an optimal value of 4.5 to minimize VIV.image

Automated summary

Seal whiskers have an undulating geometry that reduces vortex-induced vibrations (VIV) and aids in tracking prey. Research suggests that the wavelength-to-mean diameter ratio (lambda/Dm) of seal whiskers may have evolved to an optimal value of 4.5 to minimize VIV.