DNS and RANS simulations were carried out for core-annular flow in a horizontal pipe and results were compared with experiments carried out with water and oil in our lab. In contrast to most existing studies for core-annular flow available in the literature, the flow annulus is not laminar but turbulent. This makes the simulations more challenging. As DNS does not contain any closure correlations, this approach should give the best representation of the flow (provided a sufficiently accurate numerical mesh and numerical method is used). Various flow configurations were considered, such as without gravity (to enforce an on-average concentric oil core) and with gravity (to allow for eccentricity in the oil core location). Both single-phase and two-phase conditions were considered; single-phase flow refers to the water annulus with imposed wavy wall, whereas two-phase flow includes the determination of the wavy interface. Mesh refinement was carried out to assess the numerical accuracy of the simulation results.

中文翻译：

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用于具有湍流环空的核心环流的 DNS 和 RANS

对水平管道中的核心环形流进行了 DNS 和 RANS 模拟，并将结果与​​我们实验室中使用水和油进行的实验进行了比较。与文献中现有的大多数核心环形流研究相比，环形流不是层流而是湍流。这使得模拟更具挑战性。由于 DNS 不包含任何闭合相关性，因此这种方法应该给出流的最佳表示（假设使用足够准确的数值网格和数值方法）。考虑了各种流动配置，例如无重力（以强制形成平均同心油芯）和有重力（以允许油芯位置存在偏心）。考虑了单相和两相条件；单相流是指具有波状壁的水环，而两相流包括波状界面的确定。进行网格细化以评估模拟结果的数值精度。