Analysis of Storage Effects in the Recirculation Zone Based on the Junction Angle of Channel Confluence

In this study, numerical simulations using the Environmental Fluid Dynamics Code model were conducted to elucidate the effects of flow structures in the recirculation zone on solute storage based on the junction angle. Numerical simulations were performed at a junction angle of 30° to 90° with a momentum flux ratio of 1.62. The simulation results revealed that an increase in the junction angle caused the recirculation zone length and width to increase and strengthened the development of helical motion. The helical motion increased the vertical gradient of the mixing layer and the mixing metric of the dosage curves. The recirculation zone accumulated the solute as a storage zone, which formed a long tail in the concentration curves. The interaction between the helical motion and recirculation zone affected the transverse mixing, such that the transverse dispersion had a positive relationship with the helical motion intensity and a negative relationship with the recirculation zone size. Transverse mixing exhibited an inverse relationship with the mass exchange rate of the recirculation zone. These results indicate that the transverse dispersion is replaced by mixing due to strongly developed storage zones.

Conditions For Physical Modelling of The Spread of Contaminants in Groundwater

The paper contains a review of dimensionless experimental dependencies determining the coefficient of transverse dispersion Dy. In the course of the dimensional analysis, dimensionless experimental dependencies describing the dispersion of pollutants in groundwater with hydraulic and physical parameters of soil in the case of steady and uniform groundwater motion were presented. The analysis allowed the determination of dimensionless practical relationships defining the dispersion factor in the perpendicular direction to the main flow direction.

Estimation of Longitudinal and Transverse Dispersion Coefficients in Saturated Porous Media Involving Physical Model

The world's urban population growth, indiscriminate use of fertilizers and chemical poisons are actually threatening groundwater resources. The main target of this paper has been tracking of distribution of a conservative tracer in a porous media and in a laboratory-scale model, to estimate the longitudinal and transverse dispersion coefficients. In this study non-cohesive sands were used to create the porous media body in the laboratory model with a grain diameter of 1-2.5 mm. Salt (NaCl) with concentrations of 5, 7.5 and 10 g/l were used as a tracer. The results of 5g/l concentration tests are reported in this paper. An EC-meter apparatus was used to measure the EC values of the tracer to monitor its plume migration. Then the collected and recorded EC data were used to calculate the tracer concentration data in different points over time, for each test. The calculated concentration data were compared with values which were obtained from the analytical solution using Fickian second law. According to the results, for instance, in the case of 5 g/l of the tracer, the obtained values of the longitudinal and transverse coefficients are equal to 3.36e-6 and 6.58e-7 m2/s, respectively.