Experiment And Simulation Study Of Solute Transport In Two-dimensional Porous Medium Packed Lenticular Formations

The study of water flow and solute transport in porous media has been of great significance to underground engineering and groundwater pollution prevention.Tracer experiment is an important research method,but the sampling method of tracer concentration detection is mostly used in solute transport experiment.In order to avoid the influence of sampling method on solute transport,this paper presents an image analysis method to detect the concentration of tracer.In addition,most of them remained in one-dimensional transport of solute in porous media.On the basis of previous studies,a physical model is developed to simulate the solute transport of two-dimensional porous media.Inert tracers are incorporated into homogeneous porous media and porous media containing lenses,The transport of the tracer in the two-dimensional model,using the analytical model and IGW model to simulate the breakthrough curve of the solute transport under different conditions,and the numerical simulation results are analyzed and discussed.The rule and mechanism of inert solute transport are summarized.Summarized the experimental results in this paper,the following conclusions were drawn as:(1)The sampling method was replaced by image method to determine the concentration change in solute transport,we can quickly and accurately quantify the solute solubility,provide scientific simple detection method for the future research of solute movement in porous media.(2)In the experiment although the size and position of lens is varied,but the hydraulic gradient and flow rate are linear,and the traditional Darcy law is fitted.When the hydraulic gradient is same,the permeability coefficient becomes smaller with the increase of the lens body.(3)Compared with the analytical solution and IGW fitting,it can be found that in the homogeneous porous media,the fitting evaluation parameters r2 and RMSE have little difference,which can well fit the solute transport process;While in the porous medium containing lens,with the increase of the lens body,the analytical model fitting parameters of r2 decreased,RMSE increased.The r2 value and RMSE value of the IGW model have a small change,compared with the analytical solution r2 is closer to 1,the RMSE value is closer to 0,so the IGW model has higher fitting accuracy.(4)By comparing the concentration breakthrough curves under different conditions,it is found that with the increase of lens and transport distance,the peak arrival time becomes longer and the peak value becomes smaller,the diffusion coefficient D becomes larger.When the flow rate increases,the concentration reaches the peak time gradually becomes shorter and the peak value becomes larger,and the dispersion coefficient D becomes larger.It indicate that the Non-Fickian phenomena is more obvious with the velocity,lens body scale and the transport distance increases.