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G. Barth

Publications and source records attributed to G. Barth.

2 recordsLinked to original sources

Numerical methods for improving sensitivity analysis and parameter estimation of virus transport simulated using sorptive-reactive processes

Using one- and two-dimensional homogeneous simulations, this paper addresses challenges associated with sensitivity analysis and parameter estimation for virus transport simulated using sorptive-reactive processes. Head, flow, and conservative- and virus-transport observations are considered. The paper examines the use of (1) observed-value weighting, (2) breakthrough-curve temporal moment observations, and (3) the significance of changes in the transport time-step size. The results suggest that (1) sensitivities using observed-value weighting are more susceptible to numerical solution variability, (2) temporal moments of the breakthrough curve are a more robust measure of sensitivity than individual conservative-transport observations, and (3) the transport-simulation time step size is more important than the inactivation rate in solution and about as important as at least two other parameters, reflecting the ease with which results can be influenced by numerical issues. The approach presented allows more accurate evaluation of the information provided by observations for estimation of parameters and generally improves the potential for reasonable parameter-estimation results. ?? 2004 Elsevier B.V. All rights reserved.

Journal of Contaminant Hydrology

Is it More Important to Characterize Heterogeneity or Differences in Hydraulic Conductivity Measurements?

As a first step toward understanding the role of sedimentary structures in flow and transport through porous media, this work deterministically examines how transport simulations compare to observed transport through simple, artificial structures in a laboratory experiment. Small-scale laboratory-measured values of hydraulic conductivity were used to simulate transport in an intermediate-scale (10-m long), two-dimensional, heterogeneous porous medium (s 2 lnK=1.26, mlnK = 4.18, where K is cm hr-1 ). Results were judged based on how well the simulated transport matched observed transport through the tank. Permeameter and column experiments produced laboratory measurements of hydraulic conductivity for each of the five sands used in the intermediate-scale experiments. Despite explicit numerical representation of the heterogeneity, predictions using the laboratory-measured values under-estimated the mean arrival time by as much as 35%. The significance of differences between simulated and observed mean arrival time was investigated by comparing variability of transport predictions using the different measurement methods to that produced by different realizations of the heterogeneous distribution. Results indicate that the variations in measured hydraulic conductivity were more important to transport than variations between realizations of the heterogeneous distribution of hydraulic conductivity.

Conference Paper