Flexible jumper VIV simulation in uniform current
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This paper studied a flexible jumper VIV under uniform current using CFD simulation. The jumper has a total length of 265m, OD of 0.33m (L/D=800), and mass ratio of 1.0. The jumper is suspended between two fixed locations, with one end above the mean water line, and the other end below the mean water line. A uniform current of 0.5m/s was applied to its submerged section perpendicular to its catenary plane. During the CFD simulation the jumper surface and its surrounding fluid were discretized using 1.5 million elements. The flow field was solved using an unsteady Reynolds-Averaged Navier-Stokes (RANS) numerical method in conjunction with a chimera domain decomposition approach with overset grids. The riser was also discretized into 250 segments. Its motion was predicted through a simplified catenary riser motion solver that superposes a static catenary solution with a tensioned beam motion equation. The external force terms were obtained by integrating viscous and pressure loads on the riser surface. The jumper VIV behavior and vertex shedding details were studied. The VIV modal components were also extracted through a least squares method, and filtered based on transient response modal characteristics. It showed that the flexible jumper VIV was complicated by its lateral offsets, and the flexible jumper motion trajectories demonstrated random behavior. It also showed the jumper VIV could have two modes excited with similar strength. Comparisons with the results obtained by Shear 7 showed good agreement and confirmed the validity of the present CFD approach. Copyright 2011 by the International Society of Offshore and Polar Engineers (ISOPE).