基于等效渗透系数法修正的多节点井流模型

Modified MNW Model Based on Equivalent Permeability Coefficient Method

管道是含水层中十分常见的水文地质结构,目前关于含水层中地下水管道流模拟常用的模型有等效渗透系数模型、多节点井流(MNW)模型和管道流(CFP)模型,其中MNW模型和CFP模型被耦合到地下水数值模拟软件MODFLOW中。MNW模型使用有限差分网格渗透系数对管道流进行计算,在数值模拟过程中假设包含管道的含水层网格渗透系数为孔隙介质渗透系数,但其并不能反映管道-含水层网格系统的高渗透性。基于等效渗透系数法对MNW模型进行修正,为了检验修正后MNW模型的模拟效果,以二维砂槽试验数据为例,分别采用CFP模型、原始MNW模型和修正MNW模型对管道周围含水层地下水流场进行了数值模拟,并将模拟流场与实测流场进行了对比分析。结果表明:修正MNW模型与原始MNW模型相比其模拟误差降低了76.14%,且其模拟误差小于CFP模型,说明修正后的MNW模型提升了多节点井流模型对含水层中管道流的模拟效果,更好地体现了现实中管道与含水层的双重介质性,对更加高效而准确地进行含水层中地下水管道流数值模拟具有实际意义。

Conduits are ubiquitously present hydrogeological structures within aquifers.Currently,prevalent models for simulating conduit flow in aquifers include the equivalent permeability model,multi-node well(MNW)model,and conduit flow process(CFP)model.Both the MNW and CFP models are incorporated within groundwater numerical simulation software MODFLOW.The MNW model computes conduit flow using a finite-difference grid permeability and assumes that the permeability of an aquifer grid containing a conduit is the same as that of the porous medium,which fails to reflect the high permeability of the conduit-grid system.This study presents an MNW model correction based on the equivalent permeability approach.To evaluate the performance of the corrected MNW model,we conducted numerical simulations of the aquifer flow fields around the conduit using the CFP model,the original MNW model,and the corrected MNW model,using two-dimensional sandbox experiment data for comparison.The results show that the error of the corrected MNW model is reduced by 76.14%compared to the original MNW model,and the error of the corrected model is less than that of the CFP model,indicating that the corrected model enhances the simulation of conduit flow by the MNW model,and better reflects the dual-medium nature of conduits and aquifers in reality.This research has practical implications for efficiently and accurately performing numerical simulations of conduit flow.