Modeling of Air Sparging in a Layered Soil. Numerical and Analytical211 Approximations. Modelling, Analysis and Simulation

摘要

Air sparging in an aquifer below a less permeable horizontal layer is modeled211u001eusing a two-phase flow approach. Supported by numerical simulations, we show that 211u001ea steady state situation is reached. For an analysis of the steady state, we 211u001edistinguish three different flow regimes, which occur between the well screen and 211u001ethe unsaturated zone. Just below the surface that separates the high and the low 211u001epermeable layers, a regime with nearly hydrostatic capillary pressure develops. 211u001eWe use this observation to derive an ordinary differential equation for the 211u001epressure at the interface, which leads to an approximation of the air flow 211u001epatterns just below and within the low permeable layer. The approximation 211u001eprovides an estimate for the radius of influence as a function of the physical 211u001eparameters. The agreement between the analytical approximation and the numerical 211u001esteady state results is almost perfect when heterogeneity is increased. With a 211u001efew modifications, the analysis applies also to a DNAPL spills above a less 211u001epermeable layer. Comparison with an illustrative numerical simulation shows that 211u001ethe analytical approximation provides a good estimate of the radial spreading of 211u001ethe DNAPL flow on top of and within the low permeable layer.