Mixed mode transition

1228195Durbin这项研究的一般领域是流体流动从层流到湍流条件的转变。具体研究的是自由流湍流和不稳定模式对非平衡边界层转捩的影响。这与空气动力学中的应用特别相关，最重要的是飞机发动机。该研究计划解决基本问题，但它包括实际的预测方法，可用于工程设计的发展，其范围已受益于业内同行的建议。目前的研究解决的基本方面的“混合模式”之间的相互作用的影响，在边界层中引起的环境湍流和不稳定波的边界层剪切增长。然后，研究转向更具挑战性的，实际上重要的方面，这一主题，如需要半经验的技术，可用于预测的目的，在计算流体动力学代码。这项研究将扩展模型的能力，并为开发和测试这些技术提供数据。建模是实际预测能力的工程需求的具体环节。自由流湍流下的“旁路转捩”的理论和计算机模拟的概念框架以前已经导致了我们在该领域的基本理解和实际预测能力的进步。目前的项目将有助于理解和扩展我们的“混合模式”，在稳定波下发生的自由流扰动的建模能力。同样，理论观点可以从线性和弱非线性理论发展而来。为了扩展这项工作的数学框架，计算机模拟和专业数据分析技术将探索起作用的完全非线性过程。模拟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进行过渡研究。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。除了与大型数据集的经验，他们将看到流体动力学从他们的课程作业完全不同的角度。

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.