Numerical Simulation Of Fluid - Structure Coupled Vortex - Induced Vibration Of Water Separator

The marine riser is the critical pipeline equipment to the offshore oil and gas exploration&development. Vortex-induced vibration (VIV) is main causes to induce fatigue failure of marine risers, and reduce its mechanical properties significantly, finally accelerate the riser fatigue fracture. Once, the structures of marine riser are damaged, apart from massive damage to property, the leakage of oil and drilling mud will cause catastrophic damage to the marine environments. Hence, it is of great academic significance and practical value to study the mechanism of vortex-induced vibration and inhibition technology. The main work of this paper includes:(1) Based on dynamic mesh technique and user define function, two degree of freedom of fluid-structure coupling vibration of the marine riser can be realized by embeding the UDF that solves dynamic response equations in Fluent solver. The relationship between reduced velocity with drag coefficient and lift coefficient, non-dimensional amplitude, vortex shedding frequency and different modes of vortex formation are analyzed in detail, and managed to capture the phenomena of "vibration","lock-in" and "phase switch". The validity and reliability of the numerical simulation method is verified by comparing with experimental result. The mechanism of VFV and flow characteristics nearby the riser are comprehended though this numerical simulation method.(2) This numerical simulation method is applied to evaluate the efficacy of VIV control device. The two-degree of freedom of fluid-solid coupling numerical simulation research of marine riser that installed different length splitter plate on marine riser can be realized, the study found that with increase of the length of splitter plate, the efficacy of controlling VIV was getting worse, the optimal length of splitter plate is L=0.25D. Because mass ratio and damping ratio are the important parameters to VIV, the influence of different mass ratio and damping ratio on VIV also are researched.(3) The risers installing fairings also used this method to evaluate the suppression effect on VIV, different apical angle and location of fairing models are considered in this paper, the study found that the suppression effect of the fairing at the rear of riser is significantly better than that in front of riser. The optimal apical angle of fairing is θ=45°, the drag coefficient, lift coefficient and non-dimensional amplitude are dramatically reduced. The larger the apical angle of the fairing is, the worse the suppression effect is. This study has a great meaning on theory and in academic value; the two-degree of freedom of fluid-solid coupling vibration reflects the innovative research of content.