Research: Sea lions could point the way to the monitoring of riverbed erosion

A recent study conducted by Professor Christoph Bruecker and his team revealed a novel correlation in the way sea lions and rats use their whiskers to monitor underwater events that trigger riverbed erosion.

The research could make way for the online monitoring of the environmental impact of large cruiser vessels on the river bed in the shallow waters found near urban settlements such as London, Venice and Amsterdam, providing warnings of high flow speeds close to the riverbed.

The paper, titled Seal and Sea Lion Whiskers Detect Slips of Vortices Similar as Rats Sense Textures, finds that in the same way rats use their whiskers to detect textures and hard surfaces on dry land, sea lions use their whiskers to detect swirling fluid elements called vortices in the water in which they move.

Using a specially equipped water tank in City’s Aeronautical Engineering laboratory for sea lion simulations, the team mapped the typical signatures used by sea lion whiskers to detect such vortices, which signal whether prey has swum into a region.

According to Professor Bruecker, City’s Royal Academy of Engineering Research Chair in Nature-Inspired Sensing and Flow Control for Sustainable Transport, and Sir Richard Olver BAE Systems Chair for Aeronautical Engineering, “pinnipeds such as seals and sea lions use their whiskers to hunt their prey in dark and turbid situations. There is no theoretical model or hypothesis to explain the interaction between whiskers and hydrodynamic fish trails. The study, however, provides a theoretical and experimental insight into the mechanism behind the detection of the Strouhal frequency from a Von-Karman vortex street, similar to that of the inverted hydrodynamic fish trail. The flow around a 3D printed sea lion head, with integrated whiskers of comparable geometry and material properties to a real seal lion, is investigated when exposed to vortex streets generated by cylindrical bluff bodies”.

Professor Bruecker has transferred the idea of sea lion whiskers to arrays of bio-inspired optical flow sensors, which are submersible and can remotely monitor the vortices passing over the riverbed to detect strong events that may trigger erosion processes.

Having sought support from the Engineering and Physical Sciences Research Council, discussions are underway with the River Thames Restoration Trust to mark out and implement a test area on the Thames for the first trials of the monitoring system.