Approaches to the Simulation of Unconfined Flow and Perched Groundwater Flow in MODFLOW
Authors：Vivek Bedekar,Richard G. Niswonger1,Kenneth Kipp,Sorab Panday, Matthew Tonkin
Journal：Ground Water
Volumes 50,Issue 2
Date：March/April 2012
Page number：187–198
Abstract:Various approaches have been proposed to manage the nonlinearities associated with the unconfined flow equation and to simulate perched groundwater conditions using the MODFLOW family of codes. The approaches comprise a variety of numerical techniques to prevent dry cells from becoming inactive and to achieve a stable solution focused on formulations of the unconfined, partially-saturated, groundwater flow equation. Keeping dry cells active avoids a discontinuous head solution which in turn improves the effectiveness of parameter estimation software that relies on continuous derivatives. Most approaches implement an upstream weighting of intercell conductance and Newton-Raphson linearization to obtain robust convergence. In this study, several published approaches were implemented in a stepwise manner into MODFLOW for comparative analysis. First, a comparative analysis of the methods is presented using synthetic examples that create convergence issues or difficulty in handling perched conditions with the more common dry-cell simulation capabilities of MODFLOW. Next, a field-scale three-dimensional simulation is presented to examine the stability and performance of the discussed approaches in larger, practical, simulation settings.


《地下水杂志》刊登:在MODFLOW这个模拟软件中自由流和地下水流流动的模拟方法
作者: Vivek Bedekar,Richard G. Niswonger1,Kenneth Kipp,Sorab Panday, Matthew Tonkin
刊物：地下水杂志
期刊号：2012, 50(2)
时间：2012年3/4月
页码：187–198
摘要：已经提出了很多方法解决与潜水流动方程有关的非线性问题以及用MODFLOW软件的代码模拟滞水流动状况。这个方法包括各种数值方法来考虑各项动态因素以及对于受压、部分饱和地下水流动方程得到一个稳定的解决方案。K保持各项影响因素的动态性避免了得到不连续的水头，反过来提高了基于连续倒数的参数估计软件的有效性。大多数方法使牛顿 - 拉夫森线性化，以获得较好的收敛性。在这项研究中，很多已经公布的方法逐步的应用于MODFLOW作为对比分析。首先，用合成实例呈现了一种比较分析的方法，在用MODFLOW的模拟能力处理滞水状况时出现了收敛问题或困难。接下来，呈现了一个场规模的三维模拟，用来检查所讨论的方法的稳定性和性能。