标题： 高雷诺数湍流的表面采样模拟 显示英文标题

标题： Surface-sampled simulations of turbulent flow at high Reynolds number

摘要： 一种新的湍流模拟方法，该方法结合了整个流动的大型涡旋模拟（LES）和一组非空间填充的准直接数值模拟（QDNS），这些QDNS采样近壁湍流对大尺度强迫的响应，被提出并进行了评估。 该技术克服了湍流模拟的一些成本限制，因为主流动是用粗网格的LES处理的，而壁面函数则由近壁采样的QDNS提供。 测试了两个案例，摩擦雷诺数分别为Re$_\tau$=4200和20,000。 第一个案例的总网格节点数少于五十万，第二个案例少于两百万，计算仅需要一台台式计算机。 在Re$_\tau$=4200时，与已发表的DNS结果有良好的一致性，无论是平均速度剖面还是流向速度波动统计，都正确地显示了由于大尺度结构对近壁条纹的调制，近壁湍流水平显著增加。 在Re$_\tau$=20,000时趋势继续存在，并与实验结果一致，这代表了新方法的主要成就之一。 探讨了模型的多个详细方面，包括数值分辨率、LES-QDNS耦合策略和亚网格模型。 展示了QDNS和LES方面的网格敏感性较低。 由于该方法不假设壁面定律，因此原则上可以应用于非平衡流动。 显示英文摘要

摘要： A new approach to turbulence simulation, based on a combination of large-eddy simulation (LES) for the whole flow and an array of non-space-filling quasi-direct numerical simulations (QDNS), which sample the response of near-wall turbulence to large-scale forcing, is proposed and evaluated. The technique overcomes some of the cost limitations of turbulence simulation, since the main flow is treated with a coarse-grid LES, with the equivalent of wall functions supplied by the near-wall sampled QDNS. Two cases are tested, at friction Reynolds number Re$_\tau$=4200 and 20,000. The total grid node count for the first case is less than half a million and less than two million for the second case, with the calculations only requiring a desktop computer. A good agreement with published DNS is found at Re$_\tau$=4200, both in terms of the mean velocity profile and the streamwise velocity fluctuation statistics, which correctly show a substantial increase in near-wall turbulence levels due to a modulation of near-wall streaks by large-scale structures. The trend continues at Re$_\tau$=20,000, in agreement with experiment, which represents one of the major achievements of the new approach. A number of detailed aspects of the model, including numerical resolution, LES-QDNS coupling strategy and sub-grid model are explored. A low level of grid sensitivity is demonstrated for both the QDNS and LES aspects. Since the method does not assume a law of the wall, it can in principle be applied to flows that are out of equilibrium.