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Modeling Contaminant Transport in Fine Sands: Three-Dimensional Sandbox Experiments and Numerical Simulation
https://orcid.org/http://orcid.org/0000-0002-4387-7166
Transverse dispersion has been studied in the literature less than longitudinal dispersion, especially in porous media with fine and very fine sand. In this research, an experimental and numerical procedure is introduced to accurately determine dispersivity coefficients. Accordingly, three-dimensional tracer experiments (transient and steady state) are conducted in a relatively large sandbox (158 cm × 160 cm in plane and height of 70 cm), filled with a fine sand soil (D50 = 0.17 mm). The effects of different hydraulic heads and several injection concentrations are considered in the experiments. The transverse and longitudinal dispersivity are determined accurately by fitting numerical simulations to the steady-state and transient sandbox experiments, respectively. According to the results, the transverse dispersivity ranges between 0.0025 and 0.06 cm, while the longitudinal dispersivity varies from 0.15 to 0.75 cm. In addition, the ratio of transverse dispersivity to longitudinal dispersivity varies between 0.017 and 0.1, based on hydraulic gradients and solute concentrations. It was observed that the transverse and longitudinal dispersivity coefficients increase as the hydraulic gradient rises. Finally, the sensitivity analysis results show that the simulated depth–concentration curves at the steady-state condition remain approximately constant with the reasonable variations in the longitudinal dispersivity coefficient, the hydraulic conductivity, and the porosity.
Modeling Contaminant Transport in Fine Sands: Three-Dimensional Sandbox Experiments and Numerical Simulation
https://orcid.org/http://orcid.org/0000-0002-4387-7166
Transverse dispersion has been studied in the literature less than longitudinal dispersion, especially in porous media with fine and very fine sand. In this research, an experimental and numerical procedure is introduced to accurately determine dispersivity coefficients. Accordingly, three-dimensional tracer experiments (transient and steady state) are conducted in a relatively large sandbox (158 cm × 160 cm in plane and height of 70 cm), filled with a fine sand soil (D50 = 0.17 mm). The effects of different hydraulic heads and several injection concentrations are considered in the experiments. The transverse and longitudinal dispersivity are determined accurately by fitting numerical simulations to the steady-state and transient sandbox experiments, respectively. According to the results, the transverse dispersivity ranges between 0.0025 and 0.06 cm, while the longitudinal dispersivity varies from 0.15 to 0.75 cm. In addition, the ratio of transverse dispersivity to longitudinal dispersivity varies between 0.017 and 0.1, based on hydraulic gradients and solute concentrations. It was observed that the transverse and longitudinal dispersivity coefficients increase as the hydraulic gradient rises. Finally, the sensitivity analysis results show that the simulated depth–concentration curves at the steady-state condition remain approximately constant with the reasonable variations in the longitudinal dispersivity coefficient, the hydraulic conductivity, and the porosity.
Modeling Contaminant Transport in Fine Sands: Three-Dimensional Sandbox Experiments and Numerical Simulation
https://orcid.org/http://orcid.org/0000-0002-4387-7166
Transverse dispersion has been studied in the literature less than longitudinal dispersion, especially in porous media with fine and very fine sand. In this research, an experimental and numerical procedure is introduced to accurately determine dispersivity coefficients. Accordingly, three-dimensional tracer experiments (transient and steady state) are conducted in a relatively large sandbox (158 cm × 160 cm in plane and height of 70 cm), filled with a fine sand soil (D50 = 0.17 mm). The effects of different hydraulic heads and several injection concentrations are considered in the experiments. The transverse and longitudinal dispersivity are determined accurately by fitting numerical simulations to the steady-state and transient sandbox experiments, respectively. According to the results, the transverse dispersivity ranges between 0.0025 and 0.06 cm, while the longitudinal dispersivity varies from 0.15 to 0.75 cm. In addition, the ratio of transverse dispersivity to longitudinal dispersivity varies between 0.017 and 0.1, based on hydraulic gradients and solute concentrations. It was observed that the transverse and longitudinal dispersivity coefficients increase as the hydraulic gradient rises. Finally, the sensitivity analysis results show that the simulated depth–concentration curves at the steady-state condition remain approximately constant with the reasonable variations in the longitudinal dispersivity coefficient, the hydraulic conductivity, and the porosity.
Modeling Contaminant Transport in Fine Sands: Three-Dimensional Sandbox Experiments and Numerical Simulation
Iran J Sci Technol Trans Civ Eng
Ahmadizadeh, Ali (author) / Hekmatzadeh, Ali Akbar (author) / Tabatabaie Shourijeh, Piltan (author) / Baghlani, Abdolhossein (author)
2022-06-01
16 pages
Article (Journal)
Electronic Resource
English
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