Axial Dispersion Coefficients in Laminar Flows of Water-Distribution Systems

Because longitudinal dispersion is becoming increasingly germane to the problem of accurately determining water quality, water-resource managers and engineers seeking to represent solute transport in drinking-water systems must be able to compute relevant dispersion coefficients. Accordingly, the present study was undertaken to develop and experimentally verify a modified advection-dispersion-reaction transport equation as well as the formulas used to calculate the axial dispersion coefficient. The analysis assumes laminar flows, constant mean velocities, and short travel times (dimensionless time, T<0.01). With regard to the modified transport equation, the dispersion term was assumed to be direction-dependent. Thus, two distinct dispersion rates (forward and backward) were recognized and quantified as opposed to the single value used in conventional dispersion models. With the dimensionless travel time taken to be the independent variable, the developed dispersion coefficients increased at about one-fou...