A mm-Scale Aeroelastic Oscillation-Based Anemometer

By combining the aeroelastic and vortex-forced flutter modes of a thin plastic strip, its oscillation frequency can be confined to scale monotonically with fluid velocity. This principle has been used to produce a low-cost, mm-scale anemometer that measures air speed to ±(5% + 0.5m/s) from 1–18m/s. The device uses a 2mm slot-type photointerrupt detector to monitor the fundamental frequency of a 7μm thick Kapton strip suspended parallel to air flow. This paper describes the prototype and three of the experiments that informed its design. These investigated the effect of a bluff body on flutter onset velocity, the effect of filament geometry on bending position, and the effect of the superposition of the vortex-forced and aeroelastic flutter modes on discretely-measured flutter frequency. The experiments demonstrate that a trapezoidal filament in the wake of a similarly-sized bluff body is well-suited for this novel flow measurement strategy.