Dynamics of a piezoelectric beam subjected to water droplet impact with water layer formed on the surface

Rain impact energy harvesting using piezoelectric energy harvester has gained much attention recently. However, previous works have only considered the effect of single water droplet. In the case of raindrop, water would accumulate on the surface of the energy harvester and form a shallow water layer. This article models the dynamics of a piezoelectric beam, served as a raindrop energy harvester, subjected to water droplet impact with water layer formed on the surface. The impact of water droplet on the tip of the energy harvester is modelled as an impulsive force, and the water layer on the surface of the energy harvester is modelled as an added mass to the energy harvester. An attempt to model the force generated by the water ripple as a distributed load on the piezoelectric beam is presented. Numerical studies have been conducted based upon the proposed mathematical model verified by experimental results. The results showed that the presence of the water layer affects the output voltage and the dominant frequency of the energy harvester. It reveals that the effect of water (or rain) accumulation on the piezoelectric surface should be considered in deriving an optimal operating condition of such energy harvester.