Miscible Displacement of Initial Solute Distributions in Laboratory Columns

Abstract

Traditional laboratory column systems that were designed to apply tracer solution at one end of the column and collect the effluent at the other end cannot be used to study miscible displacement of initial solute distributions created by multiple inputs of the same (or different) solutes at several locations in the column. Rather, these experimental scenarios require a column system in which the tracer can be injected directly into the flow field. Miscible displacement in a laboratory column system designed for this purpose was investigated. Specifically, the influence of initial solute distributions on the breakthrough curve (BTC) was analyzed using the one‐dimensional (1‐D) convection‐dispersion equation (CDE). Numerical and experimental tests were performed to evaluate the conditions for which one can use a 1‐D Dirac delta source solution to model the initial value problem posed by miscible displacement tests in the column system. For a given outlet boundary condition, if the injected solute was distributed over a distance no larger than 5% of the distance ( L ) between the injection point and the column outlet, and the column Peclet number (Pe) was not too large (<200), the solute distribution after injection can be assumed as a Dirac delta function for solving the initial value problem.