Large Eddy Simulation Of Free Vortex-induced Motions Of A Tethered Buoyancy Can

As a typical submerged structure, Buoyancy Can is an important component of risers in deepwater oil exploitation, thereby, the motion characteristic of Buoyancy Can is of high scientific value. The practical significance of Vortex-induced motion (VIM) of low mass ratio Buoyancy Can has led to the large numbers of interesting studies.Present work encompasses two main studies: model tests of VIM of the Buoyancy Can, and using Large Eddy Simulation(LES) method to simulate the VIM of full scale Buoyancy Can,and comparing their results.1~st, model tests of VIM of Buoyancy Can are carried out. Characteristics of motion,frequency, ST number and drag coefficient are analyzed. The results show: 1)The tendency of RMS amplitude of buoyancy can in inline flow and cross flow are similar to the results of a sphere. 2)the cross flow reduced frequency increases shaping as "stairs",causing by multi-frequency. 3)Compared with the drag coefficient of fixed cylinder, when the reduced velocity is bigger than 6.19, drag coefficient of VIM increases twice.When using LES to simulate VIM, WALE (Wall-Adapting Local Eddy-viscosity Model)is selected to simulate VIM of buoyancy can. The results show: 1) results of RMS amplitude of inline flow and cross flow by model tests and WALE are similar, but results of WALE in inline can be 1.4 times of model tests, while results in cross flow is very similar to model tests.2) results of simulations are similar to that of model tests at high velocity. 3)Results of drag coefficient is more moderate than model tests. 4)the vortex modes present 2S, P+S, and 2P.Predictions of reduced velocity between 8.67 and 10.32 are done, the RMS amplitudes in inline flow increase very small, and in cross flow keep constant. Reduced frequency in both direction increase, but f_x/f_y is still around 2, ST number is 0.12 and vortex mode is 2P.This study simulated the VIM by using experimental and numerical techniques, motion characteristics of low mass ratio buoyancy can are gained, and the results indicate that LES is a precise method.