Correlation and percolation properties of turbulent diffusion

Ideas on characteristic behavior of correlation functions underlie all models of turbulent diffusion. This paper sets forth a consistent analysis of these correlation ideas, beginning with Taylor's work of 1921, which pioneered the use of the autocorrelation function, and ending with works on the percolation theory of turbulent diffusion. Despite the fact that specific physical problems are significantly different, the commonality of the theoretical notions involved is emphasized. It is shown how the ideas of 'long-range' correlations and fractality enter into the percolation method. The 'universality' of the percolation approach to the description of turbulent diffusion is discussed at some length.