Transport and pattern formation in pipe flow: theory / simulation

管流中的传输和模式形成：理论/模拟

• 批准号: 154133604
• 负责人: Professor Dr. Marc Avila Canellas
• 金额: --
• 依托单位: Zentrum für angewandte Raumfahrttechnologie und Mikrogravitation (ZARM)
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2009
• 资助国家: 德国
• 起止时间: 2008-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/154133604?language=en
• 关键词: Transport; pattern; formation; pipe; flow

In contrast to many other flows, the flow down a pipe of circular cross-section becomes turbulent despite linear stability of its laminar parabolic profile. In addition, at low Reynolds numbers turbulence does not fill the pipe but it occurs in the form of spatially localized patches, called puffs, surrounded by laminar flow. During the start of this century there has been great progress in the understanding of the turbulent transition process and the resulting turbulent state. This success has built first on the discovery of three-dimensional coherent structures that are (traveling wave) solutions of the Navier-Stokes equation and capture features of turbulent pipe flow. Another important aspect has been the observation that puffs are transient and that their decay statistics are as expected from chaotic repellers. In the first phase of this project we have described several bifurcations of coherent structures and identified the routes to chaotic motions. We have also identified the critical point for the onset of sustained turbulence that is connected with the spatial proliferation of turbulent patches in long pipes. In the second phase of the project the focus will be on identifying the global bifurcations, on characterizing the behaviour near the critical point, on developing methods to stabilize travelling waves numerically and experimentally and on developing reduced models of pipe flow. Throughout the second phase we will continue to closely interacting with experimentalists in Erlangen, Göttingen and Delft.

与许多其他流动相反，尽管其层状抛物线分布线性稳定性，但圆形横截面管道的流动变得湍流。此外，在低雷诺数下，湍流不会填充管道，而是以空间局部贴片的形式出现，称为泡芙，围绕层流流。在本世纪初，对湍流过渡过程和由此产生的动荡状态的理解取得了长足的进步。成功首先建立在发现Navier-Stokes方程的三维相干结构（行动波）解决方案和湍流流量的特征。另一个重要方面是观察到泡芙是短暂的，它们的衰减统计数据是混乱的驱虫剂所期望的。在该项目的第一阶段，我们描述了连贯结构的几个分叉，并确定了混乱运动的途径。我们还确定了与长管中湍流斑块的空间增殖有关的持续湍流发作的临界点。在项目的第二阶段中，重点将放在识别全局分叉，表征临界点附近的行为，以开发数值，实验性和开发减少管道流量模型的方法来稳定行驶波。在第二阶段，我们将继续与Erlangen，Göttingen和Delft中的实验者密切相互作用。