论文标题
在不饱和多孔介质中流量和运输的非标准模型的有效求解器
Efficient Solvers for Nonstandard Models for Flow and Transport in Unsaturated Porous Media
论文作者
论文摘要
我们研究了多孔培养基中完全耦合流量和反应性转运的几种迭代方法。所得的数学模型是一个耦合的非线性演化系统。流模型组件建立在Richards方程上,修改以结合诸如动态毛细血管和磁滞之类的非标准效应,以及溶质的反应传输方程。两个模型组件是强烈耦合的。一方面,流动会影响溶质的浓度;另一方面,表面张力是溶质的函数,它会影响毛细管压力,从而影响流动。应用EULER隐式方案后,我们考虑一组迭代线性化方案来解决所得的非线性方程,包括整体石段和两种分裂策略。后者包括规范的非线性分裂和替代线性分裂,根据我们的数值研究,总体上似乎更快地迭代。 (时间离散)系统是非线性的,我们研究了不同的线性化方法。我们考虑线性收敛的L-Scheme,它无条件地收敛,牛顿方法是四次收敛但受到初始猜测的限制。每当包括滞后效应时,牛顿方法都不会收敛。 L-Scheme收敛;然而,它可能需要许多迭代。使用安德森加速度可以改善这一方面。在MRST中实现的五个数值示例中,对不同的解决策略进行了详尽的比较,MRST是基于MATLAB的工具箱。
We study several iterative methods for fully coupled flow and reactive transport in porous media. The resulting mathematical model is a coupled, nonlinear evolution system. The flow model component builds on the Richards equation, modified to incorporate nonstandard effects like dynamic capillarity and hysteresis, and a reactive transport equation for the solute. The two model components are strongly coupled. On one hand, the flow affects the concentration of the solute; on the other hand, the surface tension is a function of the solute, which impacts the capillary pressure and, consequently, the flow. After applying an Euler implicit scheme, we consider a set of iterative linearization schemes to solve the resulting nonlinear equations, including both monolithic and two splitting strategies. The latter include a canonical nonlinear splitting and an alternate linearized splitting, which appears to be overall faster in terms of numbers of iterations, based on our numerical studies. The (time discrete) system being nonlinear, we investigate different linearization methods. We consider the linearly convergent L-scheme, which converges unconditionally, and the Newton method, converging quadratically but subject to restrictions on the initial guess. Whenever hysteresis effects are included, the Newton method fails to converge. The L-scheme converges; nevertheless, it may require many iterations. This aspect is improved by using the Anderson acceleration. A thorough comparison of the different solving strategies is presented in five numerical examples, implemented in MRST, a toolbox based on MATLAB.