【作者】 范严伟；

【导师】 马孝义；

【作者基本信息】 西北农林科技大学 ， 农业水土工程， 2008， 硕士

【摘要】 本文在查阅和分析总结国内外膜孔灌溉理论与技术研究成果的基础上,采用室内试验理论分析与数值模拟相结合,以数值模拟和试验验证为主的技术路线。以土壤水动力学理论为基础,建立了膜孔灌溉条件下的土壤水分运动模型,研究了膜孔灌溉条件下湿润体水分分布与入渗规律。通过研究得出以下研究成果:(1)采用高速离心机对试验所用中壤土和砂壤土不同容重下的土壤水分特征曲线进行了测定,采用水平土柱吸渗法测定非饱和土壤水扩散率,根据两者的实测数据,运用RETC软件对参数进行了拟合,获得了VG模型的有关参数值,表明VG模型可以很好的表征试验土壤水分特征曲线。(2)基于土壤水动力学方程,建立了膜孔灌三维土壤水分运动模型及边界条件,利用SWMS-3D软件求解;通过多组膜孔灌室内正交试验,测定其膜孔累积入渗量及土壤水分入渗动态含水量变化过程,获得土壤水分运动过程及其分布的试验数据。用所建模型对膜孔灌土壤湿润体水分分布和累积入渗量变化进行数值模拟,将模拟值与实测值进行了对比分析,结果表明:模拟值与试验值基本吻合,说明本文提出的模型和算法可用于膜孔灌入渗和湿润体特征的分析。(3)利用建立的模型,模拟多种土壤不同灌水技术要素组合下湿润体土壤水分分布和入渗量变化规律,得出在相同灌水定额条件下,初始含水量对土壤水分分布有一定影响,但对土壤湿润体的形状影响小,对膜孔累积入渗量影响微弱,灌溉水深对土壤水分湿润体的影响微弱,对膜孔累积入渗量影响较小;土壤质地、容重对土壤水分分布的影响显著,对膜孔累积入渗量影响较大;膜孔直径对土壤水分分布的影响不大,对膜孔累积入渗量影响很大;膜孔间距对土壤水分湿润体的形状影响比较大,对膜孔入渗量影响较小;开孔率对膜孔控制区域内的平均入渗水深影响大;因此在膜孔灌溉工程设计中可不考虑土壤初始含水量和灌溉水深的影响,而重点考虑不同土壤及容重条件下膜孔直径和开孔率对田间灌溉的影响。(4)根据数值模拟资料,建立了考斯加科夫公式中入渗系数k、入渗指数α与膜孔直径D和开孔率ρ之间的简化模型,通过拟合表明:入渗系数k与成线性关系,入渗指数α与开孔率ρ成线性关系。通过室内试验及已有文献资料对所建模型进行验证,结果表明:模型计算值与实测值相对偏差较小,说明所建模型能有效地描述膜孔灌点源入渗规律。更多还原

【Abstract】 This paper is based on consulting and summarizing the domestic and international film hole irrigation theory and technology, the technical route involved laboratory experiment, theoretical analysis and numerical simulation, which numerical simulation and experimental verification is the main route. Based on soil water dynamics theory, film hole irrigation soil water infiltration model is established.From the research studied above, it can be concluded that:(1) Used high-speed centrifuge to measure soil water retention curves for medium loam and sandy soil in different bulk density, the horizontal column infiltration method was used to measure the soil water diffusivity.According to both the measured data, the parameters for van Genuchten model can be obtained by using RETC software.This shows that VG model can greatly express experiment soil water retention curves.(2) Based on soil hydrodynamic equation,a 3-d soil hydrodynamic model and boundary condition is proposed for film hole irrigation,which is solved by SWMS-3D software.Through eight orthogonal tests film hole irrigation laboratory experiment,measure the film hole cumulative infiltration and dynamic water content changes of soil infiltration,we also get the water movement procession and distribution of test data.Using established model in this study, we simulate soil wetting pattern water distribution and film hole cumulative infiltration. Compared by simulated values and measured values, which have been analyzed, the results showed that the simulated values had little difference from experiment results.The model and algorithm in this paper can be used to simulate the water soil movement under film hole irrigation.(3) The soil water retention curves and infiltration capacity law in different combination is simulated by using established model.obtained conclusion that the initial water content has a certain effect on soil water distribution,has a little effect to soil water content wetting soil body and film hole cumulative infiltration;the water pressure has a distinct effect on soil water content wetting soil pattern,has a certain effect to film hole cumulative infiltration;the bulk density has a significant effect on soil water content wetting soil body,has a greater effect to film hole cumulative infiltration;the film hole diameter has a little effect on soil water distribution,has a greater effect to film hole cumulative infiltration;Film hole spacing has a greater effect on soil water content wetting soil dody,has a little effect to film hole cumulative infiltration;the opening ratio has a greater effect to cumulative infiltration of film hole control unit area;Therefore we can ignore effects of initial water content and water pressure on film hole irrigation engineering,mainly consider effects of film hole diameter and opening ratio in different bulk density.(4) According to the numerical simulation data,the relationship between the infiltration coefficient k ,the infiltration indexαof kostiakove quation and the film hole diameter D ,the opening ratioρis established.It showed that the infiltration coefficient k is linear relationship withρD0.68 and the infiltration indexαis linear relationship withρby fitting.Results of model were verified by the laboratory test and the existing literature showed that the relative deviation between the calculation value and measured value is less. The established model can effectively describe point source infiltration model for the film hole irrigation.更多还原