Calibration and validation of a harbor seal whisker-inspired flow sensor

A flow sensor inspired by the harbor seal’s whiskers has been calibrated in a towing tank and tested at sea. The whiskers’ undulatory, asymmetric geometry causes a wide range of self-excited vibrational responses. These vibrations are measured mechanically and used to determine the oncoming flow direction and velocity. Calibration runs show the vibration amplitude in the cross-flow direction to range from ≈0.1 to 0.6 times the whisker diameter, depending on the flow direction. Deflection in the inline-flow direction ranges from ≈0 to 0.08 times the whisker diameter, depending on the flow velocity. Field tests confirm the ability of the sensor to be used autonomously and at depth. Experiments with the sensor trailing a vortex generator show the sensor locking into the oncoming vortex frequency, demonstrating potential for future use as a wake detector.