Experiments And Numerical Simulations Of Soil-Water Movement In Subsurface Drip Irrigation

Subsurface drip irrigation (SDI) has been generally considered as one of "the most economical irrigation technique". But it is not used widely because of the lack of the research on the technique theory and designing principle. The rules of the soil-water movement are the base of the development and using for every irrigation technique. So study on soil-water movement of SDI has important points in improving its irrigation design and guiding its practical function. Based on the sum-up of the domestic and overseas study, the experiments and numerical simulation research of soil-water movement in SDI are studied in this thesis.Firstly, outdoor experiments are conducted to investigate soil-water distribution of SDI. An apparatus called TDR is used to measure the edge of the soil-water movement, the water content when stopping irrigation and the values after 24 hours. And the analysis about the phenomena and the results are conducted on the base of the data obtained from the experiment in this paper.Next, the VG model is used to describe the unknown parameters of the soil concerned in this thesis. And the unknown parameters introduced by the VG model itself are computed by the data measured in an indoor experiment combining the Matlab software. These parameters are the base of the simulation that followed.Then on the base of the principle of soil water dynamics and the former research, a mathematical model of soil-water movement is presented for SDI and some boundary conditions referred are discussed in this paper. In addition, the Galerkin finite element method (FEM) is used to introduce two-dimensional water flow equation simplified from three-dimensional axisymmetric SDI problem. Then numerical simulation and calculation for the soil-water movement are made by the Hydrus-2D program based on the study on the software. And the conclusions of the numerical simulation are coherent to the experiment data approximately.Lastly, the Hydrus-2D program is used to find the rules when irrigation design parameters alter. Especially, the influence of the different soil texture, trickle discharge rate and the depth trickle is buried exert on soil water movement is discussed in this paper. And the results will have some referential value for engineering design and carrying of SDI system.