Research On Characteristic Model Of Cumulative Infiltration And Wetting Pattern Movement In Film Hole Irrigation

In order to reveal the water infiltration law of film hole irrigation under free infiltration conditions and intersection infiltration conditions,based on a lot of research results of film hole irrigation at home and abroad,the paper uses a research method with combination of numerical simulation and experimental verification.Based on the theory of unsaturated soil hydrodynamics,HYDRUS-2D software is used to simulate the soil type,initial soil moisture content,film hole diameter,and irrigation head of film hole irrigation under free infiltration conditions and under infiltration conditions.The influence of factors such as film hole spacing on soil water movement characteristics.On the premise of analyzing the characteristics of film hole irrigation infiltration under different combinations of influencing factors,a simplified prediction model of film hole irrigation cumulative infiltration and a wet front migration distance were established The prediction model provides a certain theoretical reference for th e practical implementation of film hole irrigation in the field.The following main research results are obtained:?1?By analyzing the infiltration laws of different texture soils under different combinations of irrigation elements,the results show that when film hole irrigation is under free infiltration conditions,the main factors affecting its cumulative infiltration amount are soil type,film hole diameter and coverage The depth of the water head above the membrane;the factors that have a large effect on the migration distance of the wet front are mainly the soil type and membrane hole diameter.When it intersects,the main factors affecting the cumulative infiltration are soil type,membrane pore spacing,and membrane pore diameter.The other factors all have effects,but the impact is small.?2?Under the condition of free infiltration of film hole irrigation,the change law of cumulative infiltration amount accords with the Philip infiltration model.The simulation results show that the simulation parameter S absorption rate S and the film hole diameter D accord with a power function relationship,and the stable permeability A Film hole diameter D and irrigation water depth H have a good power function relationship,so a simplified calculation model for free infiltration accumulation of film hole irrigation including both film hole diameter and irrigation water depth was established.Due to the difference in soil texture The model contains two parameters to be determined,which can be obtained from a set of experimental data.?3?Moisture front migration distance under film hole irrigation free infiltration conditions includes horizontal migration distance X and vertical migration distance Y,both of which have a power function relationship with irrigation duration?R²?0.97?.For horizontal direction The coefficient of the power function increases with the increase of the sumK_s and D.In the vertical downward direction,the coefficient and index of the power function increase with the increase of the sumK_s and D.Therefore,the horizontal and vertical directions of different soils under the condition of free infiltration of film hole irrigation are established The simplified model for migration distance to the wet front requires only soil parametersK_s,and the predicted values agree well with the measured values..?4?Under the conditions of membrane hole irrigation and infiltration,the amount of reduced permeability?35?I has a power function relationship with the diameter of membrane hole D,the distance between membrane holes B and the time of reduced permeability t.The initial intersection time t₀ also has a corresponding power function relationship with B and D.Therefore,a calculation formula for the amount of infiltration reduction?35?I and the initial intersection time t₀ was established,and a simplified prediction model for the cumulative infiltration of the infiltration including the membrane pore diameter and membrane pore spacing was proposed.The cal culated value of the model was in good agreement with the measured value.The model has only two coefficients to be determined,which can be determined through a series of experiments.