参数平均方式对层状夹砂土壤积水入渗数值模拟的影响

Impact of averaging methods on the numerical simulation of pond infiltration in layered soil with sand interlayer

为研究非饱和土壤水分运动方程中参数的平均方式对层状土水分运动数值模拟的影响,采用有限差分方法对Richards方程进行离散,并用MATLAB软件编程模拟层状夹砂土柱的薄层积水入渗过程。对差分网格中半节点参数的8种不同平均方式进行了数值模拟稳定性和精度的比较。结果表明:不同平均方式下湿润峰到达某一深度的时间与该处的土壤含水量增速呈负相关关系;间接算术平均和调和平均下的土壤含水率数值振荡较大;几何平均和三点平均2种方式下入渗率、累积入渗量和湿润锋误差相对较小。综合分析,几何平均和三点平均更适合层状夹砂土情况下薄层积水入渗过程的数值模拟。

The averaging methods of parameters in Richards equation can affect numerical simulation results of water movement in layered soil.The infiltration process of layered soil column under ponding condition is simulated with MATLAB software and compared the simulation results of eight different averaging methods.The results show that there exists a negative correlation between the arriving time of wetting front and the increasing rate of soil volumetric water content at a certain soil depth.The simulated soil water content has great numerical fluctuation for the averaging methods of indirect arithmetic mean and harmonic mean.Geometric mean and triadic mean have the minimum error for simulating infiltration rate,cumulative infiltration and wetting front.In conclusion,geometric mean and triadic mean are more suitable for simulating ponded infiltration in layered soil column.