Mixed mode transition

[1228195]杜宾本研究的一般领域是流体流动从层流到湍流状态的转变。具体研究了自由流湍流和不稳定模式对非平衡边界层转捩的影响。这与空气动力学的应用尤其相关，最重要的是飞机发动机。研究计划解决基本问题，但它包括可用于工程设计的实际预测方法的发展；它的范围得益于工业界同事的建议。目前的研究解决了“混合模式”相互作用的基本方面，即由环境湍流引起的边界层扰动效应与边界层切变上生长的不稳定波之间的相互作用。然后，研究转向更具挑战性和实际意义的重要方面，如对可用于计算流体动力学代码预测目的的半经验技术的需求。本研究将扩展模型功能，并为开发和测试此类技术提供数据。建模是实际预测能力工程需求的具体环节。自由流湍流下的“旁路转换”的理论和计算机模拟的概念框架先前已经导致我们在该领域的基本理解和实际预测能力的进步。本项目将有助于理解和扩展我们的“混合模式”的建模能力，其中非稳定波发生在自由流扰动之下。同样，理论视角可以从线性和弱非线性理论中发展出来。为了扩展这项工作的数学框架，计算机模拟和专门的数据分析技术将探索完全非线性的过程。仿真还将创建用于模型开发的基准数据。这些数据将提供给社区用于过渡研究。计算机模拟将为航空航天工程专业的本科生提供数据处理和可视化的项目。除了大型数据集的经验，他们将从一个完全不同于他们的课程作业的角度来看待流体动力学。

1228195DurbinThe general area of this research is the transition of fluid flow from a laminar to a turbulent condition. The specific research is into the influence of free-stream turbulence and instability modes on transition in non-equilibrium boundary layers. This is particularly relevant to applications in aerodynamics, most importantly aircraft engines. The research program addresses basic questions, but it includes development of practical prediction methods that can be used in engineering design; its scope has benefited from advice from colleagues in industry.The present research addresses fundamental aspects of the 'mixed mode' interaction between effects of disturbances induced in the boundary layer by ambient turbulence and instability waves that grow on the boundary layer shear. The research then moves on to more challenging, and practically important aspects of this subject as such the need for semi-empirical techniques that can be used for predictive purposes in computational fluid dynamics codes. This study will extend model capabilities and provide data for developing and testing such techniques. The modeling is a concrete link to engineering needs for practical predictive ability. A conceptual framework of theory and computer simulations of 'bypass transition' under free-stream turbulence has previously lead to advances in our fundamental under- standing and practical prediction ability in that area. The present project will contribute an understanding and extend our modeling capability of the 'mixed mode', where in- stability waves occur beneath free-stream disturbances. Again, a theoretical perspective can be developed from linear, and weakly nonlinear, theory. To extend the mathematical framework for this work, computer simulations and specialized data analysis techniques will explore the fully non-linear processes at play. Simulation will also create benchmark data for use in model development. These data will be made available to the community for transition research. The computer simulations will provide projects on data processing and visualization to undergraduates in aerospace engineering. In addition to the experience with large data sets, they will see fluid dynamics from a perspective quite different from their course work.