一种精确求解Van Genuchten方程参数的有效方法

Effective method for accurate calculation of the Van Genuchten equation parameters

Van Genuchten方程参数的求解属于复杂的非线性拟合问题,传统方法解决此类问题存在着诸多弊端。本文试图找到一种精确求解方程参数的有效方法,枚举法由于列出所有可能的组合,不存在陷入局部最优值,因此被本文采用求解方程参数。首先,通过实验对比,确定目标函数指数k的取值;然后,讨论有效数字位数对方程参数及拟合精度的影响,确定方程参数的有效数字位数;最后,将枚举法与其它方法通过实验进行比较。结果表明:在目标函数、有效数字位数等相同条件下,枚举法具有最高的拟合精度,是一种精确求解Van Genuchten方程参数的有效方法。

The calculation of Van Genuchten equation parameters belongs to the complex nonlinear fitting problems.There exist a lot of disadvantages to effectively resolve these problems with the traditional methods.An effective new method is tried to accurately calculate Van Genuchten equation parameters in this paper.Brute force is proposed to calculate the equation parameters in this paper because it enumerates all the combination of four parameters and it never falls into local optimum values or early stagnation unlike other methods.First,the exponent k of objective function is chosen after the comparison between the two different values of the exponent k.Then,the influence of different effective digits on the values of equation parameters and fitting precise is discussed.Finally,the brute force compares with other methods by experiment.After much discussion,this paper draws a conclusion that the brute force is the best fitting precise of calculation of Van Genuchten equation parameters under the same conditions,such as the same objective functions,effective digits and so on.It is an effective method to accurately calculate Van Genuchten equation parameters.