中文摘要：

为研究背负式海底管线中增设的小直径附属管线对主管线的水动力影响,将大涡模拟中经典Smagorinsky亚格子模型与特征线算子分裂有限元法结合,并引入出口对流边界条件,完善了基于特征线算子分裂有限元的大涡模拟方法。通过自编程序数值模拟Re=1 000的单圆柱绕流,计算结果与相关文献吻合较好,验证了该算法计算圆柱绕流的有效性,并分析了Re=1 000时不同直径比、间距比情况下的串列双圆柱绕流,根据流场的不同涡脱落形态及两圆柱平均阻力系数、升力系数随直径比、间距比变化的规律得到了不同直径比条件下的临界间距范围。达到临界间距后,流场由单一涡脱落状态转变为双涡旋脱落状态。最后分析了两圆柱平均阻力系数及升力系数在临界间距后急剧增加的原因,为背负式海底管线的布局优化提供了理论依据。

英文摘要：

In order to study the hydrodynamic interaction influences of the small diameter auxiliary pipelines on the main pipelines linked with the piggybacking subsea transport pipeline, a numerical simulation method for the large eddy is proposed on the basis of the characteristic-based operator-splitting finite element method （ CBOS ） , combining the classical Smagorinsky model with the characteristic-based operator-splitting finite element method, and adopting the outlet convective boundary in the numerical simulation. The flow past around a single circular cylinder at Re=1000 is simulated by the program, and the calculated results well agree with the results given by the other relative literatures, which has validated the efficiency of the calculation method developed by the authors of this paper in simulating the flow past around the circular cylinder. Studies are carried out on the flow past two cylinders at Re = 1000 under the conditions of different diameter ratios and different spaces in a tandem arrangement of two cylinders and the critical spacing ranges with different diameter ratios are obtained, based on the different vortex shedding forms in the flow field and the change characteristics of the mean lift coefficients and the amplitude of the drag coefficients of the large and small cylinders with different diameter ratios and spacing ratios. The wake flow in the flow field indicates that the fluid structure becomes a two-wake shedding mode instead of a single-wake shedding mode when the gap between the two cylinders is over the critical spacing. In addition, the mean lift coefficients and the amplitude of the drag coefficients of the large and small cylinders both change sharply when the gap is larger than the critical spacing. The analyses of the reasons in the increase of the mean lift coefficients and the amplitude of the drag coefficients of the cylinders are also made when the diameter ratios are equal to 0.2 and 0.4. The research results mentioned above provide a theoretical basis for the layout op