Large-eddy simulations of complex turbulent flows

复杂湍流的大涡模拟

• 批准号: RGPIN-2016-04391
• 负责人: Piomelli, Ugo
• 金额: $ 4.23万
• 依托单位: Queen's University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=662236
• 关键词: Large; eddy; simulations; complex; turbulent

Turbulence occurs in most fluid flows. Its complexity is due to the fact that turbulent transport is mostly due to coherent, whorl-like motions (“eddies”), which are deterministic in character, but appear at random times and locations. Turbulent transport plays the primary role in determining, for instance, the drag of an aircraft or the heat transfer in a heat exchanger. Solution methods in which the eddies are explicitly resolved are gaining popularity because of the higher accuracy and completeness with which the flow can be analyzed; among them is the large-eddy simulation (LES). This proposal will focus, first, on the development of improved models and methodologies for LES, to decrease its computational demands and accelerate its transition to industry; second, on the application of LES to complex flows. My group has recently developed a new model to parameterize the small eddies [Piomelli et al., J. Fluid Mech., 766:499-527, 2015], which, in initial tests, has shown itself to be accurate and computationally cheaper than existing models. We propose to modify it to respond better to the local state of the turbulence, and extend it to more realistic flows. Furthermore, we will work towards the development of an "optimal LES" in which the computational grid adapts to the flow so that the ratio of grid size to the characteristic length-scale of turbulence is uniform. This improvement has the potential of decreasing the cost of a simulation by orders of magnitude, since present applications use grids that are overly refined in some regions and marginal in others. The second theme is the application of LES to problems of technological relevance, in which the more detailed understanding of the flow physics that LES affords in comparison to other techniques can result in significant benefits. First, we propose to study the effect of roughness on heat transfer, and explore the unknown mechanisms that determine the transport of energy, why the analogy with the transport of momentum does not hold when roughness is present, and how to model it. Second, we will investigate the flow over river dunes, extending our previous research to real-life configurations, including the sand motion and the dynamical evolution of the dune. Finally, we will apply LES to study how leading-edge protuberances can affect the performance of wings, and which shapes can improve the aerodynamic behaviour and sound emission of the wing. In summary, this proposal will take a two-pronged approach that coordinates methodological improvements, fundamental studies and applications. The model development is designed to decrease significantly the cost of the calculations, and the fundamental studies and applications will use the increased capabilities of LES to understand the physics of complex, previously unapproachable, problems. This proposal will also result in the training of at least four HQP. *****

湍流发生在大多数流体流中。它的复杂性是由于湍流运输主要是由于连贯的，类似WOREL的运动（“ Eddies”），该动作在特征上是确定性的，但出现在随机时间和位置。湍流运输在确定飞机的拖动或热交换器中的热传递方面起着主要作用。由于可以分析流量的较高的准确性和完整性，因此明确解决涡流的解决方案方法正在获得流行。其中包括大涡模拟（LES）。该提案将首先关注改进的LES模型和方法，以减少其计算需求并加速其向行业的过渡；其次，将LES应用于复杂流。我的小组最近开发了一个新模型来参数化小涡流[Piomelli等，J。流体机械，766：499-527，2015]，它是一种改进形式，已证明比现有模型更准确且计算更便宜。我们建议对其进行修改，以更好地对湍流的局部状态做出更好的反应，并将其扩展到更现实的流动。此外，我们将致力于开发“最佳LE”，其中计算网格适应流量，以使网格大小与湍流的特征长度尺度的比率均匀。这种改进具有降低模拟成本的潜力。按数量级，由于当前的应用使用某些地区过度精炼的网格，而另一些地区则是边际上的。第二个主题是将LES应用于技术相关性问题，其中对LES与其他技术相比，对LES提供的流动物理的了解更详细，可能会带来重大的好处。首先，我们建议研究粗糙度对传热的影响，并探索确定能量运输的未知机制，为什么在存在粗糙度时与动量运输的类比不存在以及如何对其进行建模。其次，我们将调查沙丘河上的流动，将我们先前的研究扩展到现实生活中的配置，包括沙丘的动态发展和动态演化。最后，我们将应用LES研究领先的突起如何影响机翼的性能，哪些形状可以改善机翼的空气动力学行为和声音发射。总而言之，该提案将采用两管制的方法，以协调方法论改进，基本研究和应用。该模型开发旨在显着降低计算的成本，基本研究和应用将使用LES的提高能力来了解复杂的，以前无法实现的问题的物理学。该建议还将导致至少四个HQP培训。 *****