非达西效应下瞬态承压无压转换数值解

Numerical solution to non-Darcian effect on transient confined-unconfined flow

为了研究承压含水层中不稳定承压无压完整井渗流转换机制,提出了一个考虑非达西效应的数值模型。利用Izbash方程描述了比流量与水力梯度之间的非线性关系,并通过有限差分法对模型进行求解。通过与达西渗流模型进行比较,验证了所提出模型的可靠性。结果表明,非达西指数、准水力渗透系数及单位储水量与非承压区的发育和含水层的降深之间呈负相关关系,这是由湍流程度的增大加速了对抽水井的补给所致。通过敏感性分析发现,降深对非达西指数、准水力渗透系数较为敏感,但对弹性储水系数和重力储水系数等不敏感。

In order to investigate the mechanism of transient confined-unconfined flow towards a fully penetrated pumping well in a confined aquifer,this study develops a numerical model considered non-Darcian effect.The Izbash s equation is used to describe nonlinear relationship between the specific discharge and the hydraulic gradient,and the numerical solution is derived by finite difference method.The acceptability of the proposed model is verified by the comparison with the Darcian seepage model.The results showed that the non-Darcian index,quasi-hydraulic conductivity and specific storage have negative effects on the development of the unconfined region and the drawdown of the aquifer,resulting from that the greater degree of turbulence flow accelerates the recharge to the pumping well.Through sensitivity analysis,it is noted that the drawdown is sensitive to the non-Darcian index,quasi-hydraulic conductivity,but not sensitive to the specific yield and specific storage.