A Self-Adaptive Planar Velocity Vector Sensor Based on Vortex-Induced Torsional Swing Motions

Flow sensing facilitates the development of fisheries and marine security. However, previously reported flow sensors can typically measure the average flow velocity within a large-scale geographical area. Herein, a self-adaptive sensor for measuring fixed-position, small area, real-time, and all-day planarly velocity vector is proposed. Based on the vortex-induced tortional swing motion mode, the arc-shaped device with a hall sensor or a piezoelectric sensor enables to recognize the 2-D magnitude and direction of the flow velocity. The working mechanism is first elaborated through the boundary layer principle of fluid mechanics. A vibration mechanical model is proposed and solved by Galerkin method to numerically investigate the relation between swing amplitude and torsional frequency for flow speed and direction sensing simultaneously. The model is subsequently validated by experiments. The proposed water velocity sensor shows a rapid response time (0.4 s) for velocity direction sensing and high linearity (1.7%) for velocity magnitude sensing. This work pioneers velocity vector sensing using Kármán vortex streets and will benefit to fixed-position, small area, real-time ocean flow sensing applications.