Experimental Study on Vortex-Induced Vibration of Rough Risers with Coupling Interference Effect Under Side-by-Side Arrangement

A vortex-induced vibration (VIV) experiment of rough risers with coupling interference effect under a side-by-side arrangement was carried out in a wave-current combined flume. The roughness of the riser was characterized by arranging different specifications of surface attachments on the surface of the riser. Rough risers with three different roughnesses were arranged side by side with smooth risers to explore the VIV response of the riser under the combined action of roughness and interference effect, and to reveal the coupling mechanism between roughness and interference effect. The experimental results show that, compared with that of a smooth riser, the VIV of a rough riser under the coupling interference effect has a wider “lock-in” region, and the displacement decreases more significantly at a high reduced velocity, which is more likely to excite higher-order modes and frequency responses. In addition, the displacement response and frequency response of the smooth riser are not significantly affected by wake interference from the rough riser, which is caused by the decrease of the wake region due to the delay of the boundary layer separation point of the rough riser.