Numerical Experiment to Analyse the Reliability of Coarse Grid Based Numerical Methods for Modelling Groundwater Flow by Drainage Objects Like Wells in Confined Aquifer

AbstractAt the neighbourhood of several drainage objects types in shallow aquifer like fully penetrated wells, partially penetrated wells, well with laterals, horizontal drainages etc. groundwater flow forms contain frequently 2D/3D singular behaviours (e.g. logarithmical or polar singularities), which require special attention by coarse grid simulations Groundwater reservoir modelling. The first objective of the paper is to test the accuracy of Finite Volume Methods with specific reference to one of the most used standard reservoir modelling software in groundwater modelling PMWIN/MODFLOW (i.e. Processing MODFLOW for Window), Chiang (2001). The numerical experiment will be accomplished mainly for fully penetrating well (W) and partially penetrating well (ppW) using various discretization size.It will be shown that the standard Well Index method (Peaceman 1983), currently used by coarse grid simulations, allows the local correction in well blocks only for hydraulic head (or pressure) in the wellbore obtained by coarse grid simulation for imposed global discharge/recharge rate of the well. In the paper an extension of the WI based method will be proposed which allows also the well discharge rate correction by coarse grid modelling for imposed hydraulic head (imposed pressure) in the well. The proposed method is proved with several numerical simulation examples for fully wells and ppWells