Fluid-Structure Interaction of Flexible Whisker-Type Beams and Its Implications for Flow Sensing by Pair-Wise Correlation

Abstract

(1) Background: Sensing of critical events or flow signatures in nature often presents itself as a coupled interaction between a fluid and arrays of slender flexible beams, such a wind-hairs or whiskers. It is hypothesized that important information is gained in highly noisy environments by the inter-correlation within the array. (2) Methods: The present study uses a model sea lion head with artificial whiskers in the form of slender beams (optical fibres), which are subjected to a mean flow with overlaid turbulent structures generated in the wake of a cylinder. Motion tracking of the array of fibres is used to analyse the correlation of the bending deformations of pairs of fibres. (3) Results: Cross-correlation of the bending signal from tandem pairs of whiskers proves that the detection of vortices and their passage along the animals head is possible even in noisy environments. The underlying pattern, during passage of a vortex core, is a jerk-like response of the whiskers, which can be found at later arrival-times in similar form in the downstream whisker’s response. (4) Conclusion: Coherent vortical structures can be detected from cross-correlation of pairs of cantilever-beam like sensors even in highly turbulent flows. Such vortices carry important information within the environment, e.g., the underlying convection velocity. More importantly in nature, these vortices are characteristic elementary signals left by prey and predators. The present work can help to further develop flow, or critical event, sensory systems which can overcome high noise levels due to the proposed correlation principle.

Sea lions could use multilateration localization for object tracking as tested with bio-inspired whisker arrays

“…We have shown via a physical demonstration, that an array of whiskers can be used as a reliable system of sensors for determining the DoA, via noise resistant GCC algorithms 12,17 , multilateration of triplets of whiskers, and using methods adapted from audio and other source localisation techniques. The relevance of this study is related to the previously reported sensing capabilities of sea lions exposed to a traveling vortex ring, passing one of the vibrissal pads on their heads 10 .…”

Sea lions could use multilateration localization for object tracking as tested with bio-inspired whisker arrays

“…We have shown via a physical demonstration, that an array of whiskers can be used as a reliable system of sensors for determining the DoA, via noise resistant GCC algorithms 12 , 18 , multilateration of triplets of whiskers, and using data processing methods adapted from audio and other source localisation techniques. The relevance of this study is related to the previously reported sensing capabilities of sea lions exposed to a traveling vortex ring, passing one of the vibrissal pads on their heads 10 .…”

“…Therefore, it is important to further research the influence of temporal coding within the array on the response. Interesting in that context is the recent study 12 with pairs of artificial whisker proving that a pair-wise cross-correlation of whiskers can decode the convection velocity. These time delays can be further used to triangulate the position of the source, using techniques adapted from radio localisation.…”

Flow-signal correlation in seal whisker array sensing

“…While the majority of past studies focused on the mechanism of single whisker sensing, little has been studied on the flow sensing at the whisker array level. During the process of sensing, seals extract flow information based on the interaction between their whisker arrays and the surrounding fluids [17,18]. With the presence of flow disturbance, each whisker can be dynamically bent in response to its hydrodynamic loading [18].…”

“…During the process of sensing, seals extract flow information based on the interaction between their whisker arrays and the surrounding fluids [17,18]. With the presence of flow disturbance, each whisker can be dynamically bent in response to its hydrodynamic loading [18]. The resulting reaction force and bending moments at the vibrissal base constitute the primary mechanical inputs to neural circuits and form the basis for vibrissotactile perception [19].…”