A NEW TIME-DOMAIN RANDOM-WALK METHOD FOR SOLUTE TRANSPORT IN 1-D HETEROGENEOUS MEDIA

A new method to simulate solute transport in 1-D heterogeneous media i s presented. This time domain random walk method (TDRW), similar in co ncept to the classical random walk method, calculates the arrival time of a particle cloud at a given location (directly providing the solut e breakthrough curve). The main advantage of the method is that the re strictions on the space increments and the time steps which exist with the finite differences and random walk methods are avoided. In a homo geneous zone, the breakthrough curve (ETC) can be calculated directly at a given distance using a few hundred particles or directly at the b oundary of the zone. comparisons with analytical solutions and with th e classical random walk method show the reliability of this method. Th e velocity and dispersivity calculated from the simulated results agre e within two percent with the values used as input in the model. For c ontrasted heterogeneous media, the random walk can generate high numer ical dispersion, while the time domain approach does not.