RAFT: A simulator for ReActive Flow and Transport of groundwater contaminants

Abstract

ErrataSince this report was written, RAFT has undergone a lot of changes so that this report does not any longer reflect the current status of RAFT. An updated report is expected to be placed on WWW in the neas future. Please send an e-mail to if you want to be notified when the report becomes available on WWW. a,chilakapati@pnl.gov SummaryThis report documents the use of the simulator RAFT for the ReActive Flow and Transport of groundwater contaminants. RAFT can be used as a predictive tool in the design and analysis of laboratory and field experiments or it can be used for the estimation of model/process parameters from experiments. RAFT simulates the reactive transport of groundwater contaminants in one-, two-, or three-dimensions and it can model user specified source/sink configurations and arbitrary injection strategies. A suite of solvers for transport, reactions and regression are employed so that a combination of numerical methods best suited for a problem can be chosen. User specified coupled equilibrium and kinetic reaction systems can be incorporated into RAFT. RAFT is integrated with a symbolic computational language MAPLE, to automate code generation for arbitrary reaction systems.RAFT is expected to be used as a simulator for engineering design for field experiments in groundwater remediation including bioremediation, reactive barriers and redox manipulation. As an integrated tool with both the predictive ability and the ability to analyze experimental data, RAFT can help in the development of remediation technologies, from laboratory to field.

Organic matter mineralization in sediment of a coastal freshwater lake and response to salinization

“…The reaction-transport model calculations were carried out with the Biogeochemical Reaction Network Simulator (BRNS), a flexible modeling environment for one-dimensional simulations (Regnier et al, 2003;Aguilera et al, 2005;Jourabchi et al, 2005). In the BRNS, the chemical species, reaction stoichiometries, kinetic parameters, boundary conditions, and transport parameters are specified by the user through a MAPLE software or web-based interface (Chilakapati, 1995;Amberg et al, 1999;Regnier et al, 2002Regnier et al, , 2003). An executable program, which consists of a set of standard routines for iteratively solving the reaction and transport equations, is then generated automatically.…”

The influence of physical heterogeneity on microbial degradation and distribution in porous media

“…The purpose of the threshold is to prevent the lag functional from being "triggered" by extremely small concentrations which arise from small-scale dispersions (real or numerical) and which may occur preceding the pulse body. The history of concentration of substrate at a particular location is incorporated into the metabolic potential functional 3 Using appropriate boundary and initial conditions of the experiment, the above system of equations was solved numerically by a high-resolution reactive flow and transport simulator RAFT [Chilakapati, 1995]. The numerical procedure involved the solution of (1) and (2) for velocities, using density and viscosity computed from the known concentration distribution at the previous time step.…”

“…A simple representation of the biomass partitioning that provides the coupling in the model is the linear reversible kinetic attachment/detachment model (equations (8) and (9)). In this model, forward and reverse rate coefficients, Kf and K r, (attachment and detachment respectively) were determined by a least squares fitting routine using RAFT (in the parameter estimation mode, [Chilakapati, 1995] …”

A Reaction-Based River/Stream Water Quality Model: Reaction Network Decomposition and Model Application

“…Equation (3) can be decomposed based on the type of reactions via the Gauss-Jordan column reduction of reaction matrix o (Chilakapati 1995). In order to avoid singularity of the reaction matrix, redundant equilibrium reactions are removed from the system prior to decomposition, so that the remaining equilibrium reactions are linearly independent (Zhang et al 2008).…”