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以下英文部分来自B. B. Mandelbrot, Possible refinement of the lognormal hypothesis concerning the distribution of energy dissipation in intermittent turbulence. Statistical Models & Turbulence, Springer, 333-351, 1972.
中文是博主的点评。
Self-similarity and the k^(-5/3) spectrum have not only been observed, but are found to hold beyond their assumed domain of applicability. An unexpected embarrassment of riches, and a puzzle!
大气湍流中能谱的-5/3律延展的范围要远远宽于结构函数2/3律,故不能仅根据能谱来判断惯性子区的范围。
For many scientists, studying turbulence is synonymous with attempting to derive its properties, including those listed above, from the Navier-Stokes equations of fluid mechanics. But one can also follow a different tack and view intermittency and self-similar statistical hierarchies as autonomous phenomena.
湍流表现出很多与复杂系统相似的特征。这些特征可能是更高层次集体行为的涌现。这就好比一个社会系统,本质上都遵循牛顿力学或量子力学和麦克斯韦方程组,但是社会的行为是更高尺度的涌现行为,根本不可能从这些方程组出发来研究。这里的尺度不仅仅表示空间尺度,还有着层次的概念。分子量级是一个层次。分子组成细胞,所有的细胞集团构成一个层次。细胞构成人体器官,所有人体器官是一个层次。个人构成家庭,所有家庭是一个层次。家庭构成国家,所有国家集团是一个层次。。。。不同的层次可以涌现出不同的行为,也可以有相似的行为。回到湍流,湍流在不同尺度上的涌现特征,也完全没必要从微团层次的Navier-Sotkes方程来理解。
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