基于二维和三维模型的盆地典型剖面流场对比

Comparison of groundwater flow fields in typical profiles in drainage basins based on 2D and the 3D models

前人多在二维剖面上分析盆地地下水循环规律,基于二维剖面模型和三维模型得到的剖面地下水流场是否一致值得探究。推导了三维单元盆地和复杂盆地的水头解析解,选取了水位最高点到最低点的剖面作为典型剖面,比较了二维、三维模型得到的典型剖面流场。当潜水面起伏关于典型剖面对称时,与三维模型相比,单元盆地二维剖面模型得到的流量随深度衰减偏慢,复杂盆地二维剖面模型得到的内部驻点位置偏深。当潜水面起伏不对称时,由于存在垂直于典型剖面的流速分量,典型剖面上不存在内部驻点,滞流区仍然存在。结论加深了对地下水在三维空间循环规律的认识。

A profile is often selected to analyze the pattern of groundwater circulation in drainage basins.However,it is unknown whether the groundwater flow field of a profile obtained from a 2D model is identical to that from a 3D model. In this paper,the analytical solutions of groundwater hydraulic heads in a unit basin and a complex basin are derived and the profile from the highest of the water table to the lowest is selected as a typical profile. The flow fields of the typical profile obtained from the 2D model and the 3D model are compared. The results indicate that when the water table is symmetric about the typical profile,compared with what obtained from the 3D model,the groundwater flux in the unit basins obtained from the 2D model decays with depth more slowly,and the internal stagnation points in the complex basins obtained from the 2D model have a greater depth. When the water table is asymmetric about the typical profile,due to the occurrence of velocity perpendicular to the typical profile,the internal stagnation points disappear,but the internal stagnant zones still exist. These results can expand the understanding of groundwater circulation in the 3D drainage basins.