Engineers at MIT have fabricated and tested a large-scale model of a harbor seal’s whisker, and identified a mechanism that may explain how seals sense their environment and track their prey. The team found that a seal’s whiskers serve two main functions in sensing the environment: first remaining still in response to a seal’s own movements through the water, and then oscillating in a “slaloming” motion in response to the turbulence left by a moving object.
In their experiments, the researchers observed that once the fabricated whisker enters the wake left by a passing object, it starts vibrating at the same frequency as the wake’s passing vortices. Careful visualizations show that the whisker “slaloms” among the vortices, like a skier zigzagging between flags. The research shows that this slaloming allows the whisker to extract energy from the wake, causing it to vibrate at the precise frequency of the wake — a mechanism that may give seals a clue to an object’s path, its size, and even its shape.
Michael Triantafyllou, the William I. Koch Professor in MIT’s Department of Mechanical Engineering, says that biologically inspired sensors, modeled after the harbor seal’s whiskers, may aid underwater vehicles in tracking schools of fish, as well as sources of pollution — a goal that he is currently working toward.
He and former graduate student Heather Beem, whose PhD thesis formed the basis of the work, have published their results in the Journal of Fluid Mechanics. Read more