In this paper, the meshless element-free Galerkin method (EFGM) based coupled model is developed to simulate the groundwater flow and multispecies reactive transport coupled with sequential decay reactions in unconfined aquifers. The use of moving least squares (MLS) approximation in approximating the head and concentration variables in EFGM tends to provide the solutions with better numerically stability than the finite difference (FDM) and finite element methods (FEM). Therefore, the proposed model is less affected by numerical dispersion unlike FDM/FEM based models. For the validation of the proposed model, it is applied to multispecies transport equations coupled with sequential reactions, reversible reactions, spatially or temporally varying transport velocities, time dependent decay rates and species concentration at the boundaries. EFGM solution is matching very well with the available analytical solutions for all the selected problems. However, FEM model fails to converge to the analytical solution for the selected problems with the time dependent transport coefficients. Finally, the developed EFGM coupled model is used to simulate groundwater flow and transport of chlorinated solvents in hypothetical and synthetic field unconfined aquifers. The EFGM solutions are compared with those from MODFLOW-RT3D simulations. The good comparison between both solutions indicates the applicability of the proposed model to multispecies transport.

本文建立了基于无网格无网格伽勒金方法（EFGM）的耦合模型，以模拟地下水在非承压含水层中的流动和多物种反应性运移以及相继的衰减反应。与最小差分法（FDM）和有限元方法（FEM）相比，使用移动最小二乘（MLS）近似法逼近EFGM中的水头和浓度变量往往可以为解决方案提供更好的数值稳定性。因此，与基于FDM / FEM的模型不同，所提出的模型受数值色散的影响较小。为了验证所提出的模型，将其应用于与顺序反应，可逆反应，时空变化的运输速度，随时间变化的衰减速率和边界处的物种浓度相结合的多物种运输方程。EFGM解决方案与针对所有选定问题的可用分析解决方案非常匹配。然而，有限元模型无法收敛到具有随时间变化的传输系数的所选问题的解析解。最后，使用已开发的EFGM耦合模型来模拟假设和合成场无限制含水层中的地下水流和含氯溶剂的迁移。将EFGM解决方案与MODFLOW-RT3D仿真的解决方案进行了比较。两种解决方案之间的良好比较表明所提出的模型对多物种运输的适用性。建立的EFGM耦合模型用于模拟假设和合成领域无限制含水层中的地下水流和氯化溶剂的输送。将EFGM解决方案与MODFLOW-RT3D仿真的解决方案进行了比较。两种解决方案之间的良好比较表明所提出的模型对多物种运输的适用性。建立的EFGM耦合模型用于模拟假设和合成领域无限制含水层中的地下水流和氯化溶剂的输送。将EFGM解决方案与MODFLOW-RT3D仿真的解决方案进行了比较。两种解决方案之间的良好比较表明所提出的模型对多物种运输的适用性。