Fundamental studies on incompressible flat-plate boundary layer and pipe flow

不可压缩平板边界层与管流基础研究

• 批准号: 341912-2010
• 负责人: Wu, Xiaohua
• 金额: $ 2.04万
• 依托单位: Royal Military College of Canada
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=572409
• 关键词: Fundamental; studies; incompressible; flat; plate

Incompressible zero-pressure-gradient boundary layer over a smooth flat-plate and incompressible flow through a smooth pipe are two fundamental building blocks of modern fluid mechanics. In the meantime, they are also the limiting cases and calibration benchmarks of many complicated engineering flows such as the boundary layer on an aircraft wing. Experiments have provided indirect evidence for the organization of large-scale vortex structures in the form of hairpin packets in the boundary layer and pipe flow. Theoreticians also hypothesized the existence of hairpin forest. Perplexingly, neither dominant hairpin packet nor hairpin forest could be detected from previous incompressible turbulent boundary layer and pipe flow simulations. We have recently achieved a breakthrough on direct numerical simulation (DNS) of flat-plate boundary layer with a natural appearance of young hairpin forest (Wu and Moin, Journal of Fluid Mechanics, Vol. 630, 2009). Top experts of the world's turbulence and boundary layer communities have expressed strong interest and have called for prompt targeted in-depth investigations (Marusic, Journal of Fluid Mechanics, Vol. 630, 2009). Here, we propose to perform fundamental investigations on the statistics and coherent structures of the flat-plate boundary layer. We also propose to investigate the large coherent structures of spatially-developing pipe flow from laminar through transition to fully-developed turbulent state. The proposed research will provide decisive and faithful resolutions to an array of pipe flow and flat-plate boundary layer questions that have been distilled from decades of experimental and theoretical investigations by many renowned groups in the world. Specific issues that will be examined include the kinematic and dynamic characteristics of hairpin forest, the physical mechanism of the very-large-scale motions indirectly observed in experiments, as well as a critical comparison of coherent structures obtained from the present DNS and previous particle image velocimetry experiments. This research will also impact the methodology of turbulence simulation.

光滑平板上的不可压缩零压力梯度边界层和光滑管道中的不可压缩流动是现代流体力学的两个基本组成部分。同时，它们也是飞机机翼边界层等许多复杂工程流的极限情况和标定基准。实验为在边界层和管道流动中以发夹包形式组织大尺度涡结构提供了间接证据。理论家们还假设了发夹森林的存在。令人困惑的是，在以前的不可压缩湍流边界层和管道流动模拟中，既不能检测到主导发夹包，也不能检测到发夹森林。