Concentration and temperature transients in heterogeneous porous media Part II: Radial transport

Being the most commonly used model of transport of solute and heat in porou s media, analytical solutions of the convection-dispersion equation are of great importance for both interpretative and numerical model validation pur poses. As in the linear case, the use of two different concentration variab les namely resident and flux concentrations are equally common in radial tr ansport; while the former is used in deriving the governing equations, the latter is the one measured in experiments. Therefore, description of transp ort processes in terms of dependent variables must be relevant to the way t racer experiments are to be performed. In addition, the common assumption o f velocity and scale dependence of dispersion coefficient also leads to mod ification in governing differential equations whether they are expressed in resident or flux concentrations. This work presents a detailed classificat ion of the solutions of convection-dispersion equation in radial coordinate s based on velocity- and/or scale-dependent forms of dispersion coefficient and also on the physical meanings of the solutions with respect to two dif ferent concentrations. The classification of solutions includes guidelines for selection of appropriate solution to be employed in field experiments a nd numerical validation as well. This classification has led to the develop ment of several new solutions in this work that are of great importance for interpreting and designing field experiments. (C) 2000 Published by Elsevi er Science B.V.