Experimental investigation on vortex-induced vibration and solid-structure impact of a near-bottom horizontal flexible pipeline in oblique shear flow

Vortex-induced vibrations and solid-structure impacts of a horizontal flexible pipeline in the vicinity bottom wall boundary are experimentally investigated water flume. A neutrally-buoyant submerged pipe, with length-to-diameter ratio about 87 fixed end supports, is subject to shear flow an oblique angle 30°. The initial gap-to-diameter between pipe equal 0.2. non-intrusive measurement high-speed cameras employed simultaneously capture space–time varying in-line cross-flow normal reduced velocity range 3–15 maximum Reynolds number 2780. Experimental results highlight new equilibrium profiles modal response branches being significantly broadened due proximity. Two solid-pipe impact features discussed, including single-segment two-segment alternating depending on dominant oscillation mode pipe. Both amplitude frequency increase velocity, resulting more frequent greater force. temporal evolution from single point contact segment observed for impact. Nevertheless, lengths two segments different as result asymmetric profile. In all cases, transversely introducing perturbation transmission along which leads multi-mode, multi-frequency asynchronous oscillations 1:1 2:1 resonance. Due momentum energy consumption, experiences slow post-impact bouncing phenomenon, contributing longer period fluid–pipe interaction