Flow-sensing mechanisms and biomimetic potential of seal whiskers

Xingwen Zheng

Research output: ThesisThesis fully internal (DIV)

653 Downloads (Pure)

Abstract

Seals can accurately track fish trails as far as 180 m away solely using ultrasensitive whiskers. A high-aspect-ratio bluff body vibrates due to its shedding vortices when the oncoming flow is present, or it is being towed in still water. However, the undulating morphology of Phocid seal whiskers can reduce vortex-induced vibrations (VIV), rendering seals highly sensitive to flow stimuli. This thesis studied the form and function of seal whiskers, involving 1) geometric parameters (the formulated 3D whisker geometry, length and thickness distributions of all whiskers on the seal muzzle, and reshaped 3D distributions of whiskers), 2) mechanical responses (vibrations in the flow and natural frequencies of seal whiskers), and 3) biomimetic potentials (the bioinspired sensor design and the optimized whisker structure). Through fluid-structure interaction (FSI) studies and experimental investigations involving seal whiskers mounted on 3D-printed microelectromechanical systems (MEMS) sensors, results revealed that neighboring whiskers in an array influenced one another by resulting in greater flow vorticity fluctuation and distribution area, thus causing increased vibrations than an isolated whisker, indicating a vibration-strengthening effect in whisker arrays. Furthermore, it was measured that the ratio (λ) of undulation wavelength to mean diameter of undulating seal whiskers was around 4.36 and 4.63 for harbor and grey seal whiskers, respectively. VIVs of seal whiskers had troughs around λ ~ 4 – 5 for grey seal whiskers, which was around the measured λ value, indicating that the ratio (λ) has evolved to an optimized value and suggesting the biomimetic design of VIV-resistant underwater structures.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • University of Groningen
Supervisors/Advisors
  • Cao, Ming, Supervisor
  • Kottapalli, Ajay, Supervisor
  • Kamat, Amar, Co-supervisor
Award date19-Dec-2022
Place of Publication[Groningen]
Publisher
Print ISBNs978-94-646-9181-8
DOIs
Publication statusPublished - 2022

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