Search

To investigate the two-dimensional dispersion characteristics of the dissolved contaminant in natural rivers, tracer experiments were performed based on the instantaneous injection of Rhodamine WT solution into small- to medium-sized rivers in Korea. The relations between the dispersion coefficients and hydraulic and geometric variables of the river were analyzed in depth. The experimental results show that transverse dispersion coefficient tends to increase as the friction term, U/U*, and the channel aspect ratio, W/H, increase. The effect of the channel curvature on the rate of transverse mixing was found to be very distinct in that DT/HU* has a linear relation with UW/U*Rc, even though the slope of the fitted line in the plot of DT/HU* versus UW/U*Rc in a log-log scale was much smaller than the slope of the equation by Yotsukura and Sayre. The longitudinal dispersion coefficient also tends to increase as U/U* and W/H increase. However, DL is rather insensitive to the channel curvature. The valu...

General behaviors based on hydraulic characteristics of natural streams and channels have been recently analyzed and developed via various numerical models. However in the states of natural hydraulics, an experimental research should be performed simultaneously with the mathematical analysis due to effects of hydraulic properties such as meander, sediment, and so on. In this study, to find effects of hydraulic characteristics and evaluate longitudinal and transverse coefficients using 2-dimensional advection-dispersion equation in meandering channels, a laboratory experimental channel has been set up with 2 S-curved sections. In addition, results of the experiments have been compared with velocity fields of same hydraulic conditions. From the analysis of the pollutant clouds illustrated from the results of tracer tests, separation, stagnation, and superposition of several pollutant clouds have been occurred from asymmetric velocity fields and effects of the secondary flow which can be estimated with using SCI (secondary current intensity). Specific relationships between hydraulic properties such as ratio of width to depth, Froude number and flow patterns with dispersion coefficients which can be well-expressed could be elucidated with 2-D routing procedure.