Non-darcian flow in a fractured aquifer

Altınörs, Adnan Altay
Non-Darcian flow in a finite fractured aquifer is studied in this thesis. A stream bounds the aquifer at one side and an impervious stratum at the other. The aquifer consists of fractures capable of transmitting water rapidly and porous blocks which mainly store water. Unsteady flow in the aquifer due to a sudden or a gradual rise in the stream level is analysed by the double-porosity conceptual model. Governing equations for the flow in fractures and blocks are developed using the continuity equation. The fluid velocity in fractures is often too high for the linear Darcian flow so that the governing equation for fracture flow is modified by Forcheimer̕s equation which incorporates a nonlinear term. Governing equations are coupled by an interaction term that controls the quasi-steady state fracture-block interflow. Governing equations are solved numerically by the Crank-Nicolson implicit scheme. The numerical results are compared to the analytical results for the same problem which assumes Darcian flow both in fractures and blocks. Numerical and analytical solutions give same results when Reynold̕s number is less than 0.1. The effect of non-linearity on the flow appears when Reynold̕s number is greater than 0.1. The larger the piezometric head gradient, the higher the flow rate and, thus, higher the non-linearity is. The effect of aquifer parameters on the flow is also investigated. The proposed model and its numerical solution is a unique application of non-linear flow models to the fractured aquifers. It can be used in predicting water levels in fractured aquifers and evaluating time dependent flow rates in the analysis of recession hydrographs.


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Citation Formats
A. A. Altınörs, “Non-darcian flow in a fractured aquifer,” Ph.D. - Doctoral Program, Middle East Technical University, 2005.