Analysis of Dispersion by the Random Walk Method

摘要

Concern about the increasing deterioration of groundwater quality has demandedthe development of engineering tools to simulate groundwater contaminant transport. Such well established numberical techniques as finite difference and finite element method were obviously chosen first to realize the first generation of transport models. At present a large number of codes exist that solve the advection-dispersion equation numerically by one of the methods mentioned above. These codes are widely used, despite the well-known fact that they produce poor results at high Peclet numbers, i.e. in cases where the advection-dispersion equation is advection dominated. In reality this situation occurs frequently. An alternative technique that is more successful at high Peclet numbers, the random walk method, has only recently recently some attention in groundwater hydrology. The thesis consists of four papers (chapters 2-5), in which the random walk method is studied. The more theoretical aspects of the method are covered in the first two chapters (2 and 3), while its use in such practical problems as transport in stratified aquifers and mixing of fresh and saline water in coastal aquifers are discussed in chapter 4 and 5. Preliminary versions of these chapters were published before as symposium papers.