Non-uniform Flow Based On Fractal Soil Experimental Study And Numerical Simulation

Heterogeneous flow is a fundamental form of the transport of water and solute in field soil. Studies on water and solute transportation can provide a reliable scientific basis for water resources utilization, agricultural soil environmental protection or pollution control. It is obviously that the traditional study method, which hypothesizes that soils are homogeneous porous media, can not accurately characterize the transport of water and solute in soil, as soil is a spatio-temporal variation continuum. Fractal dimension can token the characteristics of natural. Although its application in the physics of soil has made great progress, but the dynamic process of water and solute transport in soil not been considered in most of the related studiees. Dye tracer, which can visualize migration routes of water and solute, is an important experiment method in the non-uniform flow study of soil, but most studies digging soil pattern to get information of solute distribution in soil destroyed the pore structure and solute distribution of the original soil. Therefore, this paper makes some relative research to heterogeneous flow in soil for the above problems.In this study, Brilliant Blue was used to visualize the heterogeneous transportation on soil surface of soil samples with three different initial moisture content and three different densities. Through collecting dynamically distributed images of solute moving on soil surface by dying tests with ten minutes for the interval, the fractal dimensions of dye distribution on soil surface related to three initial moisture content were calculated respectively, and the characteristics of dye coverage and fractal dimension on soil surface with different moisture content were analyzed using binary image processing technique based on the fractal theory. Then the dynamic distribution of dye concentration on soil surface in different densities were simulated successfully by model and the calculation result well agrees with experimental data.The results suggest that:(1) For each interval, solute transportation in different structure soils exhibits distinct heterogeneities;(2) Stain areas and fractal dimension on these three different initial moisture content soils surface changed between 1.07%-4.36%,1.18%-10.27%,5.44%-25.02% and 1.5-1.64, 1.64-1.72,1.64-1.85, respectively.(3) The dynamic concentration distribution on these three different density soils changed between 0-2.782,0-2.46 or 0-2.183, respectively.Then we concluded that:compared with water flow, the solute transportation shows higher heterogeneity and uncertainty; furthermore, the observation also shows that the heterogeneous flow exhibits the behaviour of fractal; solute transportation of different moisture in soil shows heterogeneous, and these variation processes were distinct, these variation processes were all presented the nonlinear growth and the expansion degree was decrease in nonlinear with time and water infiltration; the linear correlation of dynamic concentration distribution decreased significantly with the increase of volume density, and the dye concentration distribution also decreased respectively for each time space. Based on fractal, the experimental study and numerical simulation of heterogeneous flow in soil enriched the research of water and solute transport in soil, and provide a theoretical support for the effective utilization and protection of agricultural water resources.