Numerical Simulation Study On Three-Dimensional Soil Water Infiltration Of Drip Irrigation With Two-Point Source

Drip irrigation is one of the most mature and the most easily extension water-thrift irrigation technique. Size and shape of wetted volume and distribution of soil water content is foundation of drip irrigation system.The parameters can obtained by experiment,but it waste time and labor,besides,it may be produce large error during experiment. because of natural and artificial factors. Recent years,with the rapid development of computer science,appearing numerical simulation method of basing on the theory of unsaturated soil water dynamics, it have advantages of simple, rapid, and flexible.The research into clay loam, and sandy loam analyzed effects of dripper spacing, dripper discharge, soil texture and initial water content of soil on soil water infiltration of drip irrigation with two-point source, and test the model with field demonstration.The main conclusions are as follows:(1)The relation between horizontal distance and vertical dimension of wetting front with infiltration time showing power function. The relation between horizontal transport velocity and vertical transport velocity of wetting front with infiltration time showing power function.(2)To the drip irrigation of two-point source, intersection time of wetting front showing the increase of exponential function with the increase of dripper spacing.The effects of dripper spacing vertical to transport velocity of wetting front of the intersection place is significant,but transport velocity in place of emitter has little effect.(3)With the increase of dripper spacing,shape of wetted volume Changing successively from an approximate hemispheroid to an approximate hemi anther sac, an approximate hemi peanut shell and two approximate hemispheroid. High moisture content region in wetted volume are becoming one from two. After drip irrigation(840 min),vertical dimension larger than horizontal distance.(4) After drip irrigation,transport distance of wetting front decresed with the increase of dripper discharge,but the change law of high moisture content region is opposite.The change law of the fitting coefficients between transport distance of wetting front and infiltration time:infiltration index of vertical in place of emitter decresed with the increase of dripper discharge,but the change law of intersection is opposite. The change law of the fitting coefficients between transport velocity of wetting front and infiltration time: infiltration coefficients of level and vertical in place of emitter decresed with the decrease of dripper discharge,but the infiltration index is opposite.All others no obvious regular changes.(5)Transport distance of wetting front in emitter and intersection,sandy loam soil higer than clay loam soil, and their difference increase with the increase of time. The wetting soil sandy loam soil higer than clay loam, but the volume of high moisture content region clay loam much higher than sandy loam soil. To clay loam, level and vertical distance of wetting front almost same. To sandy loam, vertical distance higer than level's.(6)Transport distance of wetting front,volume of wetting soil and volume of high moisture content region are increasing with the increase of initial water content of soil. The change law of the fitting coefficients between transport distance of wetting front and infiltration time: infiltration coefficient of level in place of emitter decresed with the increase of initial water content of soil, but intersection is opposite.Infiltration index of intersection decresed with the increase of initial water content of soil, all others are opposite.(7) verified the model by the measurement of soil moisture content, migration distance of water front, and cumulative infiltration in laboratory test. The results showed that the simulation results agreed well with measurement values. It the software of HYDRUS3D and the three-dimensionalmodel of establishment can reflect the soil water movement of clay loam conditions under drip irrigation accurately.