The roles of rigid splitter plates in flow-induced vibration of a circular cylinder

Abstract

While it is known that rigid splitter plates play significant roles in flow control, the exact roles of them in flow-induced vibration (FIV) have not been systematically investigated. This has motivated the present work to experimentally investigate the FIV of a cylinder equipped with an upstream rigid splitter plate (USP), a downstream plate (DSP), and symmetrically arranged splitter plates in a water tunnel with Reynolds number of 1100–7700. The length of the plate is in a range of L* = 0–3.6 (L*=L/D, L is the plate length, D is the cylinder diameter). The response characteristics, vortex evolution, fluid force, and pressure fields are thoroughly analyzed. Both USP and DSP can succeed in oscillation mitigation and drag reduction. However, dramatic galloping is observed for DSP with L* = 0.4–3.2. The low-pressure region forms near the downstream plate is beneficial to trigger galloping. For USP, only vortex-induced vibration is found, and the transition of response branches corresponds to the variation in oscillation frequency and phase jumps in total transverse force and vortex force. However, the vortex mode transition from 2S to 2P disappears with long plate length. Flow visualization reveals that the upstream vortex induced by USP alters the downstream vortex shedding. Furthermore, a high-pressure region forms near the tip of USP, yielding an obstructive force that suppresses the growth of oscillation. With the combination of USP and DSP, weak galloping is excited in a narrow range of L* = 1.0–1.8, and the linear increase is also broken due to the existence of USP.