Prediction of transverse dispersion coefficient using vertical profile of secondary flow in meandering channels

Abstract

When the concentration data are not available, the transverse dispersion coefficient should be predicted using the basic hydraulic parameters to analyze mixing characteristics. In meandering channels, where the secondary flow plays an important role in the increase of transverse mixing, the transverse dispersion coefficient must be predicted accounting for the vertical variation of the transverse velocity. In this study, based on the vertical distribution equation for the transverse velocity, the theoretical formula for the transverse dispersion coefficient is newly developed. The merits of the theoretical formula on the transverse dispersion coefficient derived in this study are that it has the finite combination of elementary functions so that the transverse dispersion coefficient can be easily obtained compared with other theoretical methods, and that it can take into consideration the proper shear effect of the secondary flow. To verify the theoretical prediction of the transverse dispersion coefficient, both flow and tracer experiments are conducted in the meandering laboratory channel. The predicted transverse dispersion coefficient from the newly proposed equation shows better agreement with the observed transverse dispersion coefficient than those from other exiting equations.