GROUNDWATER FLOW AND TRANSPORT SIMULATION FOR A CONFINED AQUIFER USING ANALYTIC ELEMENT METHOD AND RANDOM WALK PARTICLE TRACKING

摘要

In this paper, the groundwater flow and transport processes in a confined aquifer have been simulated using analytic element method (AEM) and random walk particle tracking (RWPT). The implementation of coupled AEM-RWPT to simulate solute transport processes is the first time in the field of groundwater flow and transport process. The AEM solves the groundwater flow equation by superposition of the analytic solution of simple hydrogeological features like, well, river, lake, recharge, etc. One of the main advantages of AEM is that, it generates continuous head and velocity, thus very suitable for particle tracking process, unlike finite difference (FD) or finite element (FE) based model where velocity needs to be interpolated from the nodal values. First using AEM, analytic elements are developed to represent pumping well, constant head boundary, no flow boundary, river, recharge etc. Thereafter, using AEM the flow processes of a hypothetical confined aquifer has been simulated. It is assumed that, there is an instantaneous injection of certain pollutant mass in the aquifer. The contaminant mass is represented by a large number of particles and solute transport process have been simulated by random walk particle tracking technique. The RWPT moves each particle by using the velocity field obtained from the AEM based flow simulation model to simulate advection and adds a random displacement to simulate dispersion. RWPT solves the transport equation directly and thus it is virtually free from numerical dispersion and artificial oscillations.