CHAPTER 14: Energy exchange between coherent fluid structures and ionic polymer metal composites, toward flow sensing and energy harvesting

Coherent fluid structures, such as vortex rings and pairs, are potential energy sources for powering small-scale electronics in underwater environments. Ionic polymer metal composites (IPMCs) are well suited as harvesting devices for scavenging energy from such coherent fluid structures due to their high compliance, ability to work in wet environments, and large electrical capacitance. In this chapter, we review recent investigations into the energy exchange between advecting coherent fluid structures and IPMCs during impact events. Experimental demonstrations include the impact of a vortex ring with a cantilever IPMC strip and with an annular IPMC. The impulsive loading from the fluid impact produces a cascade of chemo-electro-mechanical phenomena, which ultimately result in a current through the IPMC. Deeper insight into this unsteady fluid-structure interaction is obtained through analytical and numerical modeling. A fully coupled potential flow model is proposed, consisting of a Kirchhoff-Love plate immersed in an ideal fluid where a vortex pair is propagating. The potential flow model necessarily neglects fluid viscosity, which is found to play a significant role in the impact dynamics via a series of computational fluid dynamics simulations.