Vortex Structure, Inverse Cascades, and Turbulent Bursts in Rotating, Stratified Flows

旋转层流中的涡流结构、逆级联和湍流爆发

• 批准号: 9978842
• 负责人: Philip Marcus
• 金额: $ 5万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-04-15 至 2001-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9978842&HistoricalAwards=false
• 关键词: Vortex; Structure; Inverse; Cascades; Turbulent

Three-dimensional simulations of fluid turbulence in rotating and stratified flows will be carried out using spectral methods using new efficient basis functions. The calculations will increase our understanding and ability to model and calculate turbulence in anisotropy and inhomogeneous settings that are commonly found in geophysical and astrophysical flows and is many engineering applications. Rotation and stratification tend to make the fluid act nearly 2-dimensional (2D) at some locations, at some length scales, and/or for some intervals of time. It is commonly thought that when and where the flows behave as if they were fully 3D, energy is transferred ("forward cascades") from large to small scales, and small-scale turbulence acts primarily as a passive "sponge" dissipating energy. When and where the flows behave as if it were 2D, energy inverse cascades from small to large scales. In these cases the small-scale turbulence is much more complex and difficult to model, and its effects on the large-scales are more profound. A mathematical model of the inverse cascade will be developed and scaling laws for the strengths and widths of planetary jet streams will be developed and compared against simulations, experiments and observations. Asymptotics, and mathematical models for the turbulence will permit construction of new sub-grid-scale turbulence models to be used in large-eddy numerical simulations. The simulations will be compared to laboratory experiments and observations and observations of geophysical and astrophysical flows.The specific features of this investigation place it outside of the norm for most studies of turbulent/vortical motions. It is expected that the distinct results to be obtained will not only serve to illuminate the "2-D" turbulence problem but also the more general turbulent flow processes by noting the similarities/differences between the two.

旋转和分层流动中的流体湍流将使用谱方法进行三维模拟，该方法使用新的有效基函数。这些计算将增加我们对各向异性和非均匀环境中湍流的建模和计算的理解和能力，这些环境是地球物理和天体物理流动中常见的，并且是许多工程应用。旋转和分层倾向于使流体在某些位置、某些长度尺度和/或某些时间间隔内以接近2维(2D)的方式运动。通常认为，当流动表现为完全三维时，能量从大尺度转移到小尺度(“前向叶栅”)，而小尺度湍流主要起到被动“海绵”消散能量的作用。当流动表现为2D时，能量逆级联从小尺度到大尺度。在这些情况下，小尺度湍流要复杂得多，建模困难得多，其对大尺度的影响也更加深刻。我们将建立倒置叶栅的数学模型，并建立行星喷流强度和宽度的标度律，并与模拟、实验和观测结果进行比较。渐近性，以及湍流的数学模型将允许建立新的亚网格尺度的湍流模型，用于大涡数值模拟。这些模拟将与实验室实验以及对地球物理和天体物理流动的观察和观测进行比较。这项研究的特殊特点使其超出了大多数湍流/涡流运动研究的标准。预计所获得的不同结果不仅将有助于阐明“2-D”湍流问题，而且还将通过注意两者之间的相似/不同来阐明更一般的湍流过程。