基于CFP的岩溶管道流数值模拟研究——以桂林寨底地下河子系统为例

为了描述岩溶多重含水介质存在非达西流问题,研究管道流CFP模型在岩溶区数值模拟中的应用。在分析管道流CFP基本原理的基础上,通过建立概念模型算例(5个管道,上下临界雷诺数分别为2 000和4 000),探讨不同管道水文地质参数对出口流量及水流状态的影响,并对参数敏感性进行分析,最后将CFPM1模型应用于广西寨底岩溶地下河系统,探讨在实际应用中的管道流模型适用性。概念模型结果表明,参数敏感度从大到小依次为:管道直径、水力梯度、管道渗透系数、弯曲度及粗糙度,流量与雷诺数随管道参数增大而增大,水流状态从层流变为紊流。寨底岩溶管道流模型中3个观测井及地下河出口实测流量表明CFPM1能较好地模拟出岩溶地下水水位变化趋势。得出结论:CFPM1管道流模型允许岩溶管道与基岩含水层进行水流交换,能够较好地刻画岩溶区管道介质非达西流特征,但管道参数获取较为困难,且不能刻画岩溶管道形态变化。该方法具有一定通用性,可为实际应用提供指导。

Research on Numerical Simulation of Karst Conduit Media Based on CFP: A Case Study of Zhaidi Karst Underground River Subsystem of Guilin

To depict the non-Darcian and multiporosity components of flow characteristics in karst aquifers, the authors used the Conduit Flow Process (CFP) model to study the numerical simulation of karst area. For the purpose of probing into the impacts of hydrogeological parameter on discharge and water flow state and on the basis of analyzing the fundamentals of CFP, the authors established the concept model with five conduits and upper and lower critical Reynolds number being 2 000 and 4 000 respectively. Then the authors investigated a karst aquifer by applying the CFP model to discussing the applicability of the model at Zhaidi karst aquifer, a highly karstified water system located in Guilin, Guangxi. The result of applying concept model showed that discharge and Reynolds number became larger and flow state changed gradually from laminar to turbulent flow with the decreasing effect from pipe diameter, pipe conductance, hydraulic gradient, roughness to tortuosity. Zhaidi numerical model with three observation wells showed that the CFPM1 model could simulate and forecast the trend of groundwater level. It is thus concluded that CFPM1 model permits the exchange of ground water between matrix and pipe, and the non-Darcian feature of karst media could be well depicted. This method is universally applicable and practical, and can be used as the practical technology in karst numerical simulation.