Large-eddy simulation of smooth and rough-wall turbulent boundary-layer flows at arbitrary Reynolds numbers

任意雷诺数下光滑壁和粗糙壁湍流边界层流的大涡模拟

• 批准号: 1235605
• 负责人: Dale Pullin
• 金额: $ 29.98万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2016-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1235605&HistoricalAwards=false
• 关键词: Large; eddy; simulation; smooth; rough

The large-scale, computational simulation of turbulent fluid-dynamical phenomena will continue to have an enormous impact on many diverse areas of science and engineering ranging from climate modeling of planet earth, to environmental fluid dynamics and to industrial and engineering applications at large Reynolds numbers. The ideal is direct-numerical simulation (DNS) in which all relevant physical processes are properly represented and all length scales are resolved within numerical simulation. At the extreme Reynolds numbers required for many engineering applications, however, full DNS is unlikely to be practicable within the foreseeable future. The standard engineering prediction tool has been Reynolds-averaged modeling (RANS). Whilst RANS will remain useful for many applications, there exists a growing need for a more detailed but computationally tractable numerical simulation capability in engineering development work. Examples include internal pipe flows and external streamlined and bluff-body flows where physically realistic modeling of turbulent boundary-layer dynamics including transition, curvature, separation and Reynolds-number effects is required for accurate prediction. Large-eddy simulation (LES), where the large scales of turbulent motion are resolved on the computational grid while the effects of small, unresolved eddies are modeled, is intermediate between RANS and DNS. LES has been very successful for free-shear and mixing turbulence in a wide variety of settings. In unbounded flows, the large eddies carry most of the turbulent kinetic energy, dominate momentum transport and set the length and time scales that condition the small-scale turbulence dynamics. This picture is reversed near a smooth or rough wall, where the most energetically productive eddies are necessarily part of the small-scale motion. Hence despite decades of effort, the accurate numerical prediction of wall-bounded turbulent flows remains a challenging area for computational fluid dynamics. The broad objective of the present research is to construct a robust LES capability for wall-bounded flows at Reynolds-numbers typical of practical engineering interest.The project will aim to develop a subgrid-scale methodology for LES of wall-bounded turbulence with emphasis on application to spatially evolving smooth or rough-wall turbulent boundary-layer flows in the presence of favorable and adverse pressure gradients, wall curvature, laminar-turbulent transition and flow separation at essentially arbitrarily large Reynolds numbers. The novel element is a subgrid-scale wall model, based on a wall-normal integration of the stream-wise momentum equation, which enables dynamical calculation of the wall shear stress without requiring near-wall scale resolution, but which incorporates local surface roughness, wall-normal momentum transport and pressure-gradient effects. The LES modeling resulting from this work will be available for incorporation into general computational fluid-dynamics codes. It is expected that this will provide a significant advance in our capability for the numerical simulation of complex turbulent flows at very large Reynolds numbers. The research will form an important part of the education and training of individual graduate students. Additionally the work will support dissemination of the concepts and applications of modern computational engineering technology through participation in K-12 outreach programs.

紊流动力学现象的大规模计算模拟将继续对科学和工程的许多不同领域产生巨大影响，从行星地球的气候建模到环境流体动力学，再到大雷诺数下的工业和工程应用。理想的是直接数值模拟（DNS），其中所有相关的物理过程都被适当地表示，所有长度尺度都在数值模拟中得到解决。然而，在许多工程应用所需的极端雷诺数下，在可预见的未来，完全DNS不太可能实现。标准的工程预测工具是雷诺平均模型（RANS）。虽然RANS在许多应用中仍然很有用，但在工程开发工作中，对更详细但计算易于处理的数值模拟能力的需求日益增长。例子包括内部管道流动和外部流线型和崖体流动，其中需要对湍流边界层动力学进行物理逼真的建模，包括过渡，曲率，分离和雷诺数效应，以进行准确的预测。大涡模拟（LES）介于RANS和DNS之间，在计算网格上解析大尺度的湍流运动，同时模拟小的、未解析的涡流的影响。在各种环境下，LES对于自由剪切和混合湍流非常成功。在无界流动中，大涡流携带着大部分湍流动能，主导着动量输运，并设定了制约小尺度湍流动力学的长度和时间尺度。在光滑或粗糙的墙壁附近，这幅图是相反的，在那里，最具能量生产力的涡流必然是小规模运动的一部分。因此，尽管经过了几十年的努力，对壁面湍流的精确数值预测仍然是计算流体力学的一个具有挑战性的领域。本研究的主要目标是构建具有实际工程意义的典型雷诺数的壁面有界流动的鲁棒LES能力。该项目旨在开发一种用于壁面有界湍流的亚网格尺度方法，重点是应用于存在有利和不利压力梯度、壁面曲率、层流-湍流过渡和基本上任意大雷诺数的流动分离的空间演变的光滑或粗糙壁面湍流边界层流动。这种新元素是一种亚网格尺度的壁面模型，基于流向动量方程的壁法向积分，它可以在不需要近壁尺度分辨率的情况下动态计算壁面剪应力，但它包含了局部表面粗糙度、壁法向动量输运和压力梯度效应。由这项工作产生的LES建模将可用于纳入一般的计算流体动力学代码。预计这将为我们在非常大雷诺数下复杂湍流的数值模拟能力提供重大的进步。本研究将成为研究生个人教育和培养的重要组成部分。此外，这项工作将通过参与K-12外展计划来支持现代计算工程技术概念和应用的传播。