海底串列不等直径双管线水动力特性的数值研究

Numerical Simulation of Flow around Two Tandem Pipelines with Different Diameters near Seabed

应用有限体积法，结合标准湍流模型，对海底串列不等直径双管线的二维不可压缩流动进行了数值模拟。设置了小管在大管的上游和小管在大管的下游这两种工况，研究Re=20000时，串列双管在不同间距比（G／D=0．4～3）时的绕流流场、升力系数、阻力系数及＆数的变化趋势。计算结果表明：当小管位于大管上游时，大管阻力小于单根大管时的阻力，两管问距越小，差值越大，且存在一临界间距，使两管的涡脱落模式从单体模式转变为相互作用模式；当小管位于大管下游时，小间距时小管的阻力呈负值，且两管间距越小负阻力越大，两管涡脱落模式始终呈现单体模式。

Two-dimensional incompressible flow around two tandem pipelines with different diameters near the seabed is investigated numerically. The Reynolds-averaged Navier-Stokes equations are solved using finite volume method with a standard κ - εturbulence model closure at Re=20000. Two conditions are selected according to the placement of the small pipeline relative to the large pipeline. Different spacing ratio G/D between the two pipelines ranging from 0.4 to 3 is investigated. The effect of spacing ratio on the flow field and the hydrodynamic force coefficients of the pipelines is discussed. It is found that when the small pipeline is located at the upstream of the large pipeline, the drag coefficient of large pipeline is smaller than that of the isolated pipeline at the same Reynolds number, and there exists a critical spacing ratio which transits the vortex shedding from the single-mode to the interaction mode. Furthermore, when the small pipeline is located at the downstream of the large pipeline, the drag coefficient of small pipeline is negative and the smaller the spacing ratio is, the larger the negative drag coefficient is, as well as the interaction mode always appears under this condition.