Numeric simulation for flow to a pumping well with moving boundary of the non-Darcian flow region in a leaky aquifer
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In this study, groundwater flowing to a large-diameter well in a leaky aquifer has been investigated. The groundwater flow around the well were divided into two regions, Darcian flow region and non-Darcian flow region, based on the critical Reynolds number. An iteration method was proposed by using the finite difference method to estimate the interface (RcD) of these two regions. The interface is assumed to be a moving interface, meaning that RcD is a function of pumping time. The solution obtained in this study can be used to estimate the aquifer parameters when the pumping data is available. The results show that RcD is small at early pumping stage and the new solution is almost the same as that of the one-region Darcian flow model. In the middle stage of pumping, RcD increases and the difference between the new solution and the former analytical solution is relatively larger, while the slope of the drawdown-time behavior for the new solution is almost the same as that of the one-region non-Darcian flow model. For the late stage of pumping, RcD approaches a maximum value, and the new solution is almost the same as that of one-region non-Darcian flow model for the non-Darcian flow region, and it is the same as that of one-region Darcian flow model for the Darcian flow region. RcD is sensitive to the values of the radius of well casing and well screen. The new solution becomes the one-region non-Darcian flow solution when RcD approaches infinite, while it becomes the one-region Darcian flow solution when RcD approaches 0.
