Power extraction from vortex-induced vibration of dual mass system

This study theoretically examines energy extraction through the vortex-induced vibration (VIV) of a dual mass system. The theory involves a dynamic system comprising two cylinders connected with a few springs, dampers, and a generator. The governing equation for the system is composed of equations of translational motion for the two cylinders and an equation of rotation for the wake oscillator, which is introduced for describing a hydrodynamic lift force acting on a primary cylinder. The harmonic solution of the equations is derived by adopting an averaging method. The analytical solution obtained for a dual mass case is reduced to one for a single mass case by considering a limit of infinite in-between damping and zero mass of secondary cylinder. The calculation shows enhancement of power extraction by the dual mass system, surpassing that by single mass system. This advantage of the dual mass system holds under both constant and variable flow velocities.

► Energy extraction through vortex-induced vibration of a dual mass system is examined. ► The theory includes nonlinear property of VIV and oscillation of two cylinders. ► We show the relationship between single mass and dual mass systems. ► The dual mass system can extract larger energy than the single mass system. ► The dual mass system is advantageous also under variable velocity condition.