CONVOLUTION-BASED PARTICLE TRACKING METHOD FOR MODELING GROUNDWATER TRANSPORT FOR TRANSIENT FLOW CONDITIONS

A Convolution-Based Particle Tracking (CBPT) method is developed to calculate solute concentrations in groundwater models under transient flow conditions. This method is valid for linear transport processes such as first order decay or linear sorption. A pulse of particles is introduced at various times for every source location, depending on the nature of the flow. Numerical convolution of particle paths obtained at each release time and location with a time-varying source term is performed to yield the shape of the plume. The assumption of linearity allows for superposition of multiple solute sources. The CBPT method uses fewer particles for a single particle tracking run, from which source term variability, sorption and decay can all be simulated rapidly without additional process-model runs. We demonstrate the computational efficiency and numerical accuracy of the CBPT method for transient flow, for various flow and transport scenarios with special emphasis on diffusion, in a 3D porous medium.