Energy extraction from vortex-induced vibrations using period-1 rotation of an autoparametric pendulum

We propose and analyse the feasibility of extracting energy from vortex-induced vibrations using rotating motion of an attached pendulum. The resulting autoparametric pendulum system is studied primarily to understand the effect of pendulum motion on the performance of the harvester which is typically ignored to result in a simple parametric pendulum. We find that rotating motions are possible only for small values of the pendulum mass when compared with the effective mass of the vibrating structure. However, the pendulum motion reduces the basin of attraction as well as the range of system parameters corresponding to the existence of rotary solutions. This significantly alters the harvester performance. By contrast, the evolution of the pendulum coordinates (angular position and velocity) remains largely unaffected by this interaction. Hence, for the purpose of design of controllers to robustly initiate/maintain rotation from arbitrary disturbances, the simplification to a parametric pendulum is reasonable while for the design of the harvester, this exercise is completely unsatisfactory.