改进型有限分析法模拟包气带土壤水分运移  

Improved finite analytic method to simulate soil water movement in vadose zones

作　　者：张在勇[1,2] 王文科[1,2] 陆彦玮 宫程程 冉彬 武泽宇 Zhang Zaiyong;Wang Wenke;Lu Yanwei;Gong Chengcheng;Ran Bin;Wu Zeyu(Key Laboratory of Subsurface Hydrology and Ecological Effects in Arid Region,Ministry of Education,Chang’an University,Xi’an 710054,China;School of Water and Environment,Chang’an University,Xi’an 710054,China)

机构地区：[1]长安大学旱区地下水文与生态效应教育部重点实验室,西安710054 [2]长安大学水利与环境学院,西安710054

出　　处：《农业工程学报》2021年第18期55-61,共7页Transactions of the Chinese Society of Agricultural Engineering

基　　金：国家重点研发计划子课题(2020YFC1808302-004);国家自然科学基金重点项目(4213000272);国家自然科学基金青年科学基金项目(41902249);陕西省重点研发计划一般项目(2020SF-405);陕西省留学人员科技活动择优资助项目(2020006);中国地质调查局地调项目“塔里木盆地开都河-孔雀河流域源汇项参数体系调查评价”(2021西地委3-08)。

摘　　要：近年来有限分析法被广泛应用于模拟土壤水分运移。混合型有限分析法通常使用一阶有限差分近似代替Richards方程中的时间导数项。尽管这种方法与其他的数值方法(例如有限差分法)相比,能获得精确度更高的数值解,但是当需要精细刻画陡峭湿润锋面向下传输过程时,需要对时间项的处理提出更高的要求。因此,该研究提出一种从时域和空间域获取局部解析解的改进型有限分析计算格式来克服上述问题。将改进的有限分析法的数值解、混合型有限分析的数值解、有限差分数值解与解析解定量化对比研究发现,改进型有限分析计算格式在较大空间步长条件下(空间步长为10 cm),能够获得精度较好的数值解,且能更好地控制质量平衡误差。此外,改进的有限分析法能获得与现有的软件(VSAFT2)相似的计算结果。该研究能为包气带水分运移模拟提供一种可靠的方法,推动区域土壤水资源的评价与管理。Finite Analytic Method(FAM)has widely been used to solve the Richards equation in recent years.The first-order finite difference approximation can usually be utilized in the hybrid FAM(HFAM)to handle the time derivative term during solution.To some extent,the HFAM can obtain satisfactory results,compared with other numerical methods,such as the modified picard Finite Difference(MPFD)method.However,large errors can also be found using the HFAM to simulate the characteristics of sharp wetting fronts during the infiltration process in the vadose zone.Therefore,a better method is required to handle the time derivative term.In this study,an improved FAM(IFAM)was proposed to accurately simulate the soil water movement in the vadose zone.The IFAM was selected to obtain local analytic solutions from both the time and space domain simultaneously,due mainly to totally different from the HFAM method.Three cases were also considered to systematically evaluate the performance of IFAM.In all cases,the one-dimensional vertical soil columns were set as 100 cm.In the first case,the upper boundary condition was a constant flux boundary,and the lower boundary was a constant pressure head.Three soil columns were discretized into 100,50,and 10 elements,respectively.The Finite Difference Method(FDM),HFAM,analytic solution,and IFAM were utilized to solve the Richards equation for better comparison.In the second case,both upper and lower boundary conditions were constant pressure heads.The vertical discretization spacing was set as 1 cm.The water movement was then simulated in the vadose zone using IFAM and VSAFT2(a commonly-used software based on the Finite Element Method(FEM)to solve the Richards equation).In the third case,the upper boundary condition was also assumed to be a flux boundary,and the flux was equal to the amount of evaporation and rainfall.The lower boundary condition was a constant pressure head.The results of the first case showed that the best numerical results was achieved in the IFAM among all numerical methods.Fur

关 键 词：土壤 水分 运移 有限分析法 包气带 数值模拟 

分 类 号：P641[天文地球—地质矿产勘探]