Spatially Variable Dispersion Coefficients in Meandering Channels

To analyze the spatial variability of two-dimensional dispersion coefficients in meandering channels, an observed dispersion tensor was calculated by applying a theoretical equation to the measured velocity profiles of two laboratory channels. From the observed dispersion tensor, local longitudinal and transverse dispersion coefficients were estimated by the least squares method. In both channels, the spatial variation in the dispersion coefficients was found to be strongly dependent on the specific location within the channel, because alternating bends in channels induces the periodic generation of secondary currents that alter the magnitude of transverse dispersion. Dimensionless transverse dispersion coefficients of each measurement section vary from 0.33 to 1.14 for the M1 channel and from 0.63 to 3.40 in the M2 channel around the entrance and apex of the second bend. The maximum negative correlation occurred near the apex of the channels because of the separation of the point of maximum primary velocity and the center of the circulation cells by the complex flow structure in the meandering channel. DOI: 10.1061/(ASCE)HY.1943-7900.0000669. (C) 2013 American Society of Civil Engineers.