Three-dimensional numerical investigation of a transversely oscillating slotted cylinder and its applications in energy harvesting

Abstract

The present paper numerically investigates the fluid dynamics associated with the flow over an elastically mounted circular cylinder at a Reynolds number of 500. A slit normal to the flow direction is placed at the cylinder's centre. The study covers the large parametric set of calculations for the combined mass-damping ratio $m^{*}\zeta = 0.2$ , including the slit offset for six different offset angles ( $-30^\circ \leq \alpha \leq +30^\circ$ ) measured from the vertical axis at the centre point of the cylinder and the effect of slit widths ( $0.1 \leq s/D \leq 0.3$ ) on the aerodynamic loading, vibration response and associated flow characteristics. Furthermore, a wide range of reduced velocities ( $3\leq U_r \leq 7$ ) are examined for the complete closure of studying the effect on the vortex-induced vibration response. The results demonstrate that adding the normal slit increases the periodic suction-blowing phenomena, strengthening the vortex shedding. The results suggest that the normal slit can suppress or increase vortex-induced vibration depending on the slit-offset angle. Placing it toward the front stagnation point results in the increased oscillation amplitude (with a wider wake behind the cylinder) while shifting it toward the rear stagnation point diminishes the cylinder's oscillations. The paper reveals that this dual behaviour of the normal slit (based on its offset placement) is closely related to the phase difference between the lift force and the oscillation amplitude. Various vortex-shedding patterns associated with the different slit-offset angles are duly reported in the paper. Furthermore, a magnet is attached to the slit cylinder, and its effect on the energy harvesting capability via a coil-magnet arrangement is explored in detail for a wide range of reduced velocities.