Linearized cosimulation of hydraulic conductivity, pressure head, and flux in saturated and unsaturated, heterogeneous porous media

An efficient cosimulator is developed for generating both random hydraulic property fields and related flow regimes under either saturated or unsaturated conditions. This cosimulator combines a spectral random field generator, based on the Fast Fourier Transform technique, and first-order perturbation/spectral solutions for flow in saturated and unsaturated porous media. Owing to the first-order approximation of the simulator, flow regimes in several geological media with different variabilities are simulated to investigate the accuracy of the simulator. For mild and moderately heterogeneous geological media, the simulator is found to be very accurate in terms of pressure head field and flux distributions. In addition, the execution time of the simulator is substantially smaller than that of any classical numerical simulator. However, the accuracy of the simulator deteriorates as the geological medium becomes highly heterogeneous.