The tertiary distribution

The complexity of a model increases as we proceed from the primary to the tertiary distribution and as the number of spatial dimensions that are considered increases. Essentially all published solutions have been reduced to one or two dimensions, and most include only simulations of the primary and secondary current distributions. For the special case in which only mass transport is limiting, a large number of correlations for the current distribution are available. 

The tertiary distribution represents the formal thin boundary layer solution with no farther approximation. 

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