(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) Conclusions: 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.

Previous behavioural research on live sea lions has shown that they are able to detect the direction of oncoming vortices, even when impacting contralaterally. These experiments showed that the whisker system and the animal’s neural processing is seemingly able to detect the Direction of Arrival (DoA) from just one side of the heads vibrissal pads. Therefore, temporal differences between whisker stimulation is a likely method for determining the angle. Herein, a theoretical model is presented based on multilateration, and tested by experimental studies on a 2D array of bio-inspired whiskers with regular spacing, and a 3D array of bio-inspired whiskers on a model head of a sea lion, as used in our previous studies. The results show that arrays of whiskers can in principle work as antennae to determine the DoA. This detection of the DoA is achieved by cross-correlation of triplets of whiskers, and Time Difference Of Arrival based multilateration, a method similar to signal processing in modern communication systems and other source localization applications. The results on the 2D array are conclusive and clearly support the hypothesis, while increased uncertainties were found for the 3D array, which could be explained by structural shortcomings of the experimental model. Possible ways to improve the signal are discussed.

(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.

Previous behavioural research on live sea lions has shown that they are able to detect the direction of oncoming vortices, even when impacting contralaterally.These experiments showed that the whisker system and the animal's neural processing is seemingly able to detect the Direction of Arrival (DoA) from just one side of the heads vibrissal pads. Therefore, temporal differences between whisker stimulation is a likely method for determining the angle. Herein, a theoretical model is presented based on multilateration, and tested by experimental studies on a 2D array of bio-inspired whiskers with regular spacing, and a 3D array of bio-inspired whiskers on a model head of a sea lion, as used in our previous studies. The results show that arrays of whiskers can in principle work as antennae to determine the DoA.This detection of the DoA is achieved by cross-correlation of triplets of whiskers, and Time Difference Of Arrival (TDOA) based multilateration, a method similar to signal processing in modern communication systems and other source localization applications. The results on the 2D array are conclusive and clearly support the hypothesis, while increased uncertainties were found for the 3D array, which could be explained by structural shortcomings of the experimental model. Possible ways to improve the signal are discussed.