Low-dimensional dynamics of a turbulent wall flow
Low-dimensional dynamics of a turbulent wall flow
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DOI：
10.1017/s0022112001004050
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发表时间：
2001-05
影响因子：
3.7
通讯作者：
J. Jiménez;M. Simens
中科院分区：
文献类型：
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作者：
J. Jiménez;M. Simens
用数值模拟的方法研究了湍流壁流中结构的低维动力学特性。它们既是“最小”的，因为它们包含每个相关结构的单一副本，也是“自主”的，因为它们不存在可以与之相互作用的外部湍流。这种相互作用是通过一个数值掩模来防止的，该掩模对给定壁距以上的流动进行了抑制，并研究了作为掩模高度的函数的流动特性。所发现的最简单的情况是沿流传播的波不变地传播。当数值掩蔽函数的高度小于δ+1≈50时，它表现为单个波状低速条纹的形式，两侧是两个反向旋转的交错准流向涡。随着掩模高度的增加，这个解分成一个近乎完美的极限环、一个双频环面、弱混沌和完全边缘爆发的湍流。当δ+1≈70时，过渡基本上完成，即使计算盒子的与墙壁平行的维度足够小，以至于爆发的湍流是亚稳定的，只持续几个爆发周期。类似的低维动力学可以在更大一些的盒子里找到，盒子里有两个基本结构的副本，在这个盒子里爆发的湍流是自我维持的。
The low-dimensional dynamics of the structures in a turbulent wall flow are studied by means of numerical simulations. These are made both ‘minimal’, in the sense that they contain a single copy of each relevant structure, and ‘autonomous’ in the sense that there is no outer turbulent flow with which they can interact. The interaction is prevented by a numerical mask that damps the flow above a given wall distance, and the flow behaviour is studied as a function of the mask height. The simplest case found is a streamwise wave that propagates without change. It takes the form of a single wavy low-velocity streak flanked by two counter-rotating staggered quasi-streamwise vortices, and is found when the height of the numerical masking function is less than δ+1 ≈ 50. As the mask height is increased, this solution bifurcates into an almost-perfect limit cycle, a two-frequency torus, weak chaos, and full-edged bursting turbulence. The transition is essentially complete when δ+1 ≈ 70, even if the wall-parallel dimensions of the computational box are small enough for bursting turbulence to be metastable, lasting only for a few bursting cycles. Similar low-dimensional dynamics are found in somewhat larger boxes, containing two copies of the basic structures, in which the bursting turbulence is self-sustaining.