《Simulation and Modeling of Turbulent Flows》
1. There is no vertex stretching in two-dimensional turbulence; instead, vortices coalesce to form larger vortices, and this is the mechanism for energy transfer.
二维湍流中没有涡的拉伸，与之对应的是，大涡是由小涡合并产生。（引申意思就是不像三维湍流，能量的传递是从大涡到小涡，而是反其道而行之，也就是所谓的Backscatter）
2. In 1941, Kolmogorov suggested that, as the energy was passed from wavelet to wavelet, it would lose detailed information about the mechanism of energy production. If the number of seteps in the cascade was sufficiently great, we could presume that all information would be lost. They might be expected to be isotropic(having lost all information about the anisotropy of the energy-containing scales)
K41理论说：在能量在小波之间传递时，逐步会丧失本身所携带的信息，也就是他的各向异性。不过需要明白的时，这种假设就是存在于雷诺数无限大，任何计算的雷诺数都不可能无线大，所以这种假设也就仅仅存在于想象中，即便有些计算里的雷诺数相当大，但是只能说他的小尺度只是接近各项异性，而不能说完全。
3. Homogeneous turbulence is observed to be approximately Gaussian in the energy containing scales( turbulence is never Gaussian in the small scales, due to the spectral transport, but more about that in the next section). A Gaussian distribution has all zero third moments, and hence all fluxes of the form will be zero and hence
will vanish.
齐次湍流在含能尺度附近是高斯性的，但是小尺度从来都不可能是高斯型，因为谱输运的作用。高斯型分布导致所有的三阶距都是0，因此后边这两项都会消失。
4. In a homogeneous flow, all transport vanishes, since the transport terms are of the form of a divergence, and spacial derivatives are all zero in a homogeneous situation.
齐次湍流中，所有的输运项都会消失，因为输运项通常都是由散度形式组成，但是空间导数在齐次条件下都为0.
5.
