滴灌条件下土壤水分运动规律的研究

Study on water movement under trickle Irrigation

本文根据滴灌条件下土壤水分运动的实际状态,提出了描述平面流运动的数学模型.采用ADI法和Newton-Raphson法联合运用求解数学模型,并编写FORTRAN程序在长城-0520计算机上实现数值计算.在室内进行了不同滴头流量的模型实验.二者结果都表明,滴头流量越大,滴头附近形成的饱和区和水平方向湿润锋的运移距离也越大;水平方向和垂直方向湿润锋的最大运移与入渗时间平方根存在着线性关系;任意时刻湿润锋形状可用半椭圆形方程表示.这些结论,对合理设计滴灌系统具有一定的理论意义和实用价值.

Based on the condition of trickle irrigation, a plane flow model is developed. The model is solved by combining ADI difference procedure with Newton-Raphson method. A FORTRAN program is presented. Experiments are conducted in the laboratory, and calculations are also made. The results indicate that discharge rates have remarkable effect on soil water movement, an increase in trickle discharge rate results in an increase of the ponded area around the nozzle, consequently an increase of the horizontal wetted area and a decrease of the soil wetted depth. It is also found that the maximum value of the wetting front in both horizontal and vertical directions is linearly related to the square root of the infiltration time. The shape of the wetting front at any infiltration time can be expressed by semielliptical equation.