Discovering the Transition Mechanisms in Fundamental Canonical Flows and in Idealized Propulsion Component Systems

流动从确定性层流状态过渡到随机湍流状态的过程在智力上具有挑战性，在技术上也很重要，注意到表面摩擦，表面传热和声发射的水平在过渡之前，期间和之后都有明显的不同。我们的研究计划集中在发现层流到湍流过渡机制的基本规范流以及应用航空工程系统的统一主题。典型的过渡流包括Blasius边界层的自然和旁路过渡（大多数人都知道），以及百年未解决的Osborne Reynolds管过渡，而应用的航空过渡流可以在涡轮定子转子级中找到，它形成了喷气发动机推进系统的构建块。我们希望通过专注于两个方面来建立一个高度创新和有影响力的研究计划：确定国际流体研究界普遍和深刻兴趣的主要前沿，未解决的问题;开发和使用高度准确，经过彻底验证的最先进的调查方法，即超大规模，物理现实，空间发展直接数值模拟（DNS）。 我们最近的研究结果发表在《流体力学年度评论》、《美国国家科学院院刊》和《流体力学杂志》上。我们的DNS数据已被全世界的管流和边界层研究人员用作基准。 在这里，我们建议提高我们的研究计划，以解决新的挑战，是重要的流体力学领域进行基本的机制调查的精确动态过渡在奥斯本雷诺管流过渡，冯卡门旋转盘边界层过渡，和多模式过渡流在一个理想化的涡轮机叶片转子级的中跨部分。 我们的愿景是解决主要的未解决的基本和工程过渡流问题，使我们的发现可以纳入未来的本科和研究生教科书。Osborne Reynolds管过渡，von Karman旋转盘过渡和理想化定子-转子级中的多模过渡的确定的目标问题构成了一个连贯的研究主题，专注于过渡建模的潜在工程相关性的机制。我们的方法是创新的，因为我们执行空间发展，非常大规模的DNS从层流开始，通过过渡，一直到完全发展的湍流。拟议的发现计划推动了最先进的边界，推动了过渡研究领域的发展，使我们能够与世界上一些最好的团体进行国际竞争。

The processes of flow transitioning from a deterministic laminar state to a stochastic turbulent one are both intellectually challenging and technologically important, noting that the levels of skin-friction, surface heat transfer and sound emission are all markedly different before, during and after the transition. Our research program centers on the unifying theme of discovering laminar-to-turbulent transition mechanisms in fundamental canonical flows as well as in applied aeronautical engineering systems. Canonical transitional flows include the Blasius boundary layer’s natural and bypass transition (mostly understood), and the century-old unresolved Osborne Reynolds pipe transition, whereas applied aeronautical transitional flows can be found in a turbomachinery stator-rotor stage, which forms the building block of jet engine propulsion system. We aspire to building a highly innovative and impactful research program by focusing on two aspects: identify major cutting-edge, unresolved problems that are of general and profound interest to the international fluids research community; develop and use highly accurate, thoroughly validated, state-of-the-art investigative approach, namely, very-large-scale, physically-realistic, spatially-developing direct numerical simulation (DNS). Our recent results have been published at the Annual Review of Fluid Mechanics, Proceedings of the National Academy of Science of the United States of America, and the Journal of Fluid Mechanics. Our DNS data have been used worldwide as benchmarks by pipe flow and boundary layer researchers. Here, we propose to elevate our research program to address new challenges that are important to the field of fluid mechanics by performing fundamental mechanism investigations on the precise dynamics of transition in the Osborne Reynolds pipe flow transition, the von Karman rotating disk boundary layer transition, and the multi-mode transitional flow in the mid-span section of one idealized turbine vane-rotor stage. Our vision is to tackle major unresolved fundamental and engineering transitional flow problems so that our discoveries could be incorporated into future undergraduate and graduate textbooks. The identified target problems of Osborne Reynolds pipe transition, von Karman rotating disk transition, and multi-mode transition in idealized stator-rotor stage constitute a coherent research theme focusing on the mechanisms with potential engineering relevance for transition modeling. Our approach is innovative in that we perform spatially-developing, very-large-scale DNS start from laminar, through transition, all the way to fully-developed turbulence. The proposed discovery program pushes the boundary of the state-of-the-art, moves the transition research field forward, and enables us to compete internationally with some of the best groups in the world.