Piezoelectric wind velocity sensor based on the variation of galloping frequency with drag force

Abstract

In this paper, we demonstrate a miniature energy harvesting wind velocity sensor of simple, low-cost construction, based on a single-degree-of-freedom galloping structure. The sensor consists of a prismatic bluff body with a triangular cross section attached to the free end of a cantilever incorporating a commercial polyvinylidene fluoride piezoelectric film. In the wind, the bluff body causes vibration of the cantilever based on galloping, and the piezoelectric film converts the vibration energy into an electrical signal. We have observed a negative correlation between the wind velocity and the vibration frequency, and we demonstrate that this relationship can be used to detect wind velocity directly with useful accuracy. A simple theoretical model indicates that the frequency shift can be accounted for by the effect of the axial loading due to form drag. The model shows close agreement with the experimental results. In wind tunnel tests, a prototype wind velocity sensor based on this principle could measure wind velocities from 4.45 to 10 m/s, with the measured velocity typically being within 4% of the reference value obtained using a Pitot tube.