Reduced order modeling of the Newton formulation of MODFLOW to solve unconfined groundwater flow
Reduced order modeling of the Newton formulation of MODFLOW to solve unconfined groundwater flow
复制标题
DOI：
10.1016/j.advwatres.2015.06.005
复制
发表时间：
2015-09-01
影响因子：
4.7
通讯作者：
Yeh, William W-G.
中科院分区：
文献类型：
--
作者：
Boyce, Scott E.;Nishikawa, Tracy;Yeh, William W-G.
基于投影的模型降阶技术已被证明是非常有效的，以减少高维地下水模拟的计算负担，但只适用于承压地下水流。提出了一种新的方法，减少了离散，瞬态，无压地下水流模型的维数。这种无约束模型降阶技术是基于Galerkin投影和MODFLOW的牛顿公式。该方法的实现遵循标准的包设计和代码结构，MODFLOW采用其所有功能。当在MODFLOW中调用该包时，它可以收集快照，生成基础，构建简化模型并及时向前传播简化模型。新的配方准确地代表了地下水位表面下的各种非线性设置，如井内流从多节点井。无约束模型降阶应用于四个测试用例，以说明其在处理非线性特征的灵活性。几个测试案例进行了讨论，以证明无侧限模型简化的适用性。最后一个测试用例将新的模型简化方法应用于由113，578个单元组成的圣巴巴拉，CA的范围MODFLOW模型，该模型每个时间步需要求解113，578个方程，并将其简化为127个方程。(C)2015爱思唯尔有限公司版权所有。
Projection-based model reduction techniques have been shown to be very effective for reducing the computational burden of high dimensional groundwater simulations, but only applied to confined groundwater flow. A new methodology is proposed that reduces the dimension of a discretized, transient, unconfined groundwater flow model. This unconfined model reduction technique is based on Galerkin projection and the Newton formulation of MODFLOW. The method is implemented following the standard package design and code structure that MODFLOW employs for all its features. When the package is invoked within MODFLOW it can collect snapshots, produce a basis, construct the reduced model and propagate the reduced model forward in time. The new formulation accurately represents the water-table surface under a variety of nonlinear settings, such as intraborehole flow from a Multi-Node Well. The unconfined model reduction is applied to four test cases to illustrate its flexibility in handling nonlinear features. Several test cases are discussed to demonstrate the unconfined model reduction applicability. The final test case applies the new model reduction methodology to a scoping MODFLOW model of Santa Barbara, CA composed of 113,578 cells, which requires solving 113,578 equations per time step, and reduces it to 127 equations. (C) 2015 Elsevier Ltd. All rights reserved.