A study of surface mixing in a meandering channel using GPS floaters

A particle-tracking experiment using surface floats was conducted to better understand the characteristics of a floating pollutant mixture in meandering channels. The experiments were performed in a life-size scale experiment center that can replicate natural flow structures. The experimental flume includes sinuosities of 1.2, 1.5, and 1.7. Surface mixing was analyzed with respect to these sinuosity values. The surface float was designed to represent the mixing by surface flow. The trajectories of the floats were recorded by built-in GPS. From the positions of the GPS floaters, the longitudinal and transverse diffusion coefficients were calculated using the moment method. The results of the calculations show that the dimensionless longitudinal diffusion coefficient ranges from 5.94 to 14.55 and the dimensionless transverse diffusion coefficient ranges from 0.37 to 2.61. These results suggest that the mixing of floating pollutants has directional properties in the meandering channels due to shear flow. Furthermore, the relationship between the longitudinal diffusion coefficient and the integral timescale was found to have a linear relationship in accordance with Taylor’s theory.