Kinematic modeling of multiphase subsurface transport.

摘要

Fluids that are immiscible with water form one phase of a multiphase flow system when introduced into the subsurface. Simplified modeling of such fluids provides means to estimate the bulk movement of pollutants over time, but in the past such models have relied on assumed shapes for fluid profiles in the soil. Kinematic models of soil moisture transport provide an alternative where the soil moisture profile is obtained through solution of the governing equations. Kinematic models also provide a means to study the wave nature of the flow, which is a problem that is difficult to solve by traditional finite element or finite difference methods. The objective of this research was to apply kinematic theory to multiphase pollutant events resulting from spills or land treatment sites. The resulting model formulations are entirely in the form of a system of coupled nonlinear ordinary differential equations, which are solved by a Runge Kutta technique. Two FORTRAN implementations are presented, one (KOPT--Kinematic Oily Pollutant Transport) for situations where the water flux is represented by a constant value. The second (KROPT--Kinematic Rainfall and Oily Pollutant Transport) allows interactions between the oil and subsequent rainfall events to be modeled. The latter work showed that oil banks form and move ahead of the incoming water as it displaces the oil. Example simulations are presented for both models, and a set of experimental land treatment results are compared with KROPT simulations.