Dynamic response of a cylinder-plate-cylinder system coupling wake-induced and interference effects

This study proposes a flow-induced vibration (FIV) configuration consisting of two transversely oscillating cylinders with a square plate positioned between them (cylinder–plate–cylinder, C-P-C system) to investigate the coupling between wake-induced and wake-interference effects. Numerical simulations are conducted using the immersed boundary adaptive mesh refinement (IBAMR) framework at a Reynolds number of 150, mass ratio of 2, and zero damping. The relative location of the plate and downstream cylinder is parameterized by the upstream spacing ratio (SPU) between the upstream cylinder and the plate, and the downstream spacing ratio (SPD) between the plate and the downstream cylinder. This study considers SPU = 0.5, 0.7, 1.0, and SPD = 1–5. Compared to the isolated cylinder (IC) and cylinder–cylinder (C-C) systems, the C-P-C system induces a broader range of dynamic responses characterized by seven distinct regimes. Three combinations of the seven response regimes are proposed at different SPUs. At SPU = 0.5, full wake-interference galloping is observed and is coupled with wake-induced vibration or galloping across all SPD, driven by lift instability, the amplification of the lift force component at three times the fundamental oscillation frequency (3fosc), and the in-phase lift-displacement interaction. For SPU = 0.7, wake interference galloping is not fully initiated but is suppressed due to the dominant lift component at 3fosc and anti-phase lift. At SPU = 1, galloping is absent, yet the vortex-induced vibration (VIV) lock-in regime extends from reduced velocity Ur = 5–7 (C-C and IC systems) to Ur = 5–10. A critical range of spacing ratio (SP) = 2.9–3.2 is identified in the C-C system, characterized by a sudden drop in force coefficients and response amplitude of the downstream cylinder. This transition corresponds to the downstream cylinder moving beyond the upstream cylinder's vortex separation region, where the wake-induced effect weakens.