Characteristic scales large Peclet number

Equation (9) generalizes earlier porosity-Peclet number power-law correlations (Konstandopoulos et al., 2002) obtained at Pe > 0.3 down to the diffusion limited deposition limit. PeQ is a characteristic cross-over Peclet number defining the scale beyond which the convective mechanism will take over the diffusive mechanism of deposition and eK the large Peclet number asymptote of the porosity. K has a dependence on the aggregate size and it is described in a forthcoming publication (Konstandopoulos, 2007). Using Eq. (9) the experimental data of Fig. 9 can be collapsed on a single curve as shown in Fig. 10. 

An important characteristic of a property distribution is encapsulated in the Peclet number, Pe = ULIk, which is the ratio of diffusive time-scale to advective timescale of the system. In this definition, U and L are the characteristic velocity and length scales of the flow. The Peclet number is a measure of the relative importance of advection versus diffusion, where a large number indicates an advectively dominated distribution, and a small number indicates a diffuse flow. Numerical modeling indicates that certain tracer distributions, in particular tracer-tracer relationships, are significantly affected by the Peclet number, and consequently can be used to determine the nature of the fluid flow (Jenkins, 1988 Musgrave, 1985, 1990). 

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