Verification of the inverse model: multi-step steady-state outflow method using numerical and experimental data

Abstract

The multi-step steady-step steady-steady outflow method (MSSOM), an inverse model, is developed by Muller [ 1992] as a practical alternative over more labor intensive techniques for the rapid measurement of unsaturated hydraulic conductivity. The MSSOM method employs the steady-state Darcy's equation for parameter estimation. This method requires only three easily-measured flux controlled attributes including flow rate, suction and core length from a one dimensional short column experiment. A multistart-adaptive simplex (MSX-ARS) technique is employed to locate the objective function's global minima. A number of experimental, and noiseless and noisy numerical data sets are employed to verify the MSSOM method in this study. The MSSOM method performs well if the data is noiseless. However, this method is found sensitive to errors in flow rate and core length. Furthermore, lengthy computer time is required for the MSX-ARS approach. Therefore, additional refinement of the MSSOM experimental setup and minimization technique are needed to further improve this method.