Energy conversion evaluation of a cylinder-plate-cylinder harvester coupling wake-interference and induced vibrations: effects of spacing and damping ratio

A system consisting of two cylinders undergoing transverse oscillations with a rigid plate positioned between them, known as the cylinder–plate–cylinder (C-P-C) arrangement, can enhance the response through coupled wake-interference and wake-induced mechanisms. To examine how non-zero structural damping affects the system dynamics and energy-harvesting performance, the present work conducts a systematic parametric analysis of the upstream spacing ratio (SPU = 0.5 and 0.7), the downstream spacing ratio (SPD = 1–3), and the damping ratio (ζ = 0.1–0.3). Their influences on the structural dynamics, hydrodynamic forces, and energy-harvesting characteristics of the C-P-C configuration are examined, with particular attention to the flow–structure interaction mechanisms underlying the observed performance differences. Immersed boundary simulations with adaptive mesh refinement are conducted at Re = 150 and m∗ = 2 over Ur = 3–30 using the open-source IBAMR toolbox. For comparison, cylinder–cylinder (C-C) and an isolated cylinder (IC) systems are also examined. Seven evaluation metrics are adopted to assess energy-harvesting performance, including peak nondimensional power, efficiency, and power density, together with overall averaged output power and efficiency (OAOP and OAOE) and their corresponding improvements relative to the IC. The results show that, compared to the C-C system, the interference plate extends the lock-in region of the upstream cylinder from Ur = 5–6 to Ur = 5–15 and enables wake-interference galloping at high reduced velocities when the damping ratio remains below 0.2. Among the configurations considered, the most favorable C-P-C cases are concentrated around (SPU, SPD) = (0.7, 2–3), and the case (0.7, 2) provides the strongest combined performance because it couples sustained upstream-cylinder wake-interference response with strong wake-induced vibration of the downstream cylinder. Within the investigated parameters, this favorable C-P-C configuration maintains competitive total performance over a relatively broad damping range of ζ = 0.15–0.25, and the case at ζ = 0.2 achieves a peak total nondimensional power of about 0.33. Using overall-averaged metrics over the considered Ur range, the representative (SPU, SPD) = (0.7, 2) configuration yields ΔOAOP = 281% and ΔOAOE = 364% at ζ = 0.15. Although the C-C system performs strongly at small spacing ratios and high damping and remains superior in several total-averaged metrics, the C-P-C system offers the highest peak total power, stronger upstream-cylinder harvesting, and a broader favorable damping window within the present low-Reynolds-number numerical framework.