Experimental investigation on flow-induced vibration control of flexible risers fitted with new configuration of splitter plates

Experimental investigations within the Reynolds number range of 2600–9100 were performed to examine the effectiveness of serrated splitter plates in controlling the flow-induced vibration (FIV) of flexible risers. Conventional splitter plates were arranged for contrast to highlight the unparalleled features of the new splitter plates. Bending strains of FIV responses were measured and converted into critical parameters of displacement, dominant frequency, oscillation orbit, suppression efficiency, and fatigue damage for analysis. Test results illustrate that for flexible risers with conventional or serrated splitter plates, a galloping phenomenon occurs at a low reduced velocity, and standing wave characteristics invariably dominate their FIV responses. As the reduced velocity varies increasingly, the conventional splitter plate triggers a continuous monotonous increase in the FIV amplitudes of controlled risers. However, owing to the phase difference in the interaction of the shear layers between proximal plates and distal plates, the FIV amplitudes of the risers fitted with serrated splitter plates start to stay constant virtually and then distinctly decline with appearing chaotic oscillation trajectories. Moreover, the control performance of serrated splitter plates with uniformly distributed serrations in alleviating FIV amplitudes is optimal at high reduced velocities; whereas excessively dense or sparse serrations can reduce FIV inhibition.