基于FlexPDE的膜孔灌土壤水分运动数值模拟

Numerical simulation of soil water transport under film-hole irrigation based on FlexPDE

基于实测扩散率资料和土壤水分特征曲线,利用FlexPDE软件对膜孔灌溉的土壤水分运动进行模拟,探索恒定水头条件下膜孔灌溉土壤水分入渗特性和剖面水分分布特征。结果表明:FlexPDE软件模拟粉粘壤土(处理2、3)和砂壤土(处理1、4)的含水率与实测之间的平均相对误差分别为5.930%、8.340%、9.600%和14.040%,其中粉粘壤土模拟与实测土壤含水率相对误差小于5%、10%和20%的比例分别为40%、68%和84%,砂壤土相对误差小于5%、10%和20%的比例分别为12%、40%和72%,粉粘壤土的模拟效果较砂壤土理想;基于模拟获取的土壤储水量与土壤实测累积入渗量呈线性关系,相关系数均大于0.9,且二者与入渗时间呈幂函数关系,随入渗时间增加而增大,但增速逐渐变缓;利用FlexPDE预测分析膜孔间距、膜孔直径和入渗水深对粉粘壤土膜孔灌溉单向交汇时刻、水分分布和储水量的影响,发现膜孔间距对于交汇初期土壤的水分分布影响较大,膜孔直径对于土壤交汇时间以及储水量影响显著。

To explore the applicability of FLexPDE, characteristics of infiltration, and water distribution in soil profile under film-hole irrigation with a constant pressure head, the soil water transport was simulated by FlexPDE with the measured soil diffusivity and soil water characteristic curve. The results showed that: The mean relative errors between the measured moisture content and the FlexPDE simulated of silty clay loam (treatments 2 and 3) and sandy loam (treatments 1 and 4) were 5.930%, 8.340%, 9.600%, and 14.040%, respectively. In terms of the relative error between simulation and the measured soil moisture content of silty clay loam, less than 5%, 10% and 20% were 40%, 68%, and 84%, respectively. For the sandy loam, less than 5%, 10%, and 20% were 12%, 40%, and 72%, respectively. Therefore, the simulated effect of silty clay loam is better than sandy loam. Accumulated infiltration had a good linear correlation with simulated water storage, and the correlation coefficients were all greater than 0.9. Meanwhile, the accumulated infiltration and water storage grew in function of power along with increasing time, but the increase rate slowed. Using FlexPDE to predict and analyze the impact of hole spacing, hole diameter, and infiltration depth on the unidirectional intersection moment, water distribution, and water storage of mulching hole irrigation in silty clay loam, it was found that the hole spacing had a great impact on the soil water distribution at the initial intersection stage, and the diameter of film hole had a significant impact on the soil intersection time and water storage.