Thomson N R, Johnson R L
Department of Civil Engineering, Faculty of Engineering, University of Waterloo, ON, Canada.
J Hazard Mater. 2000 Feb 25;72(2-3):265-82. doi: 10.1016/s0304-3894(99)00143-0.
The performance of in situ air sparging is controlled by the distribution of air pathways in the subsurface, which is in turn controlled by the structure of the medium to be sparged. The specific pathways that the air follows are determined, at the grain scale, by the distribution of air entry pressures of the pores. At the field scale, pore size distributions are usually correlated with heterogeneous structures (e.g. layers) within the medium, which control the macroscopic distribution of the air. The processes that produce an observed air distribution at a particular site are complicated, and are potentially well suited to modeling with multiphase flow models. Recent numerical modeling of heterogeneous media appears to successfully represent expected distributions of air; however, current models do not provide a tool to predict sparging performance. For this to be the case, the models need to represent the detailed structure of the medium at the site to be studied, as well as to capture the relevant aspects of the discrete air/water distribution (i.e., represent air channels at the centimeter or smaller scale). This will, in general, require a level of site data that is not available and numerical models that require many millions of computational elements. As a consequence, at least for the foreseeable future, numerical modeling of the air sparging process will continue to play a vital role as a conceptual tool with limited predictive capability at sites.
原位空气注入的性能受地下空气通道分布的控制，而空气通道分布又受待注入介质结构的控制。在颗粒尺度上，空气所遵循的具体通道由孔隙的进气压力分布决定。在现场尺度上，孔径分布通常与介质内部的非均质结构（如地层）相关，这些结构控制着空气的宏观分布。在特定地点产生观测到的空气分布的过程很复杂，并且可能非常适合用多相流模型进行模拟。最近对非均质介质的数值模拟似乎成功地再现了预期的空气分布；然而，目前的模型并未提供预测注入性能的工具。要做到这一点，模型需要表示待研究地点介质的详细结构，同时捕捉离散的空气/水分布的相关方面（即表示厘米级或更小尺度的空气通道）。一般来说，这将需要目前尚无法获得的现场数据水平以及需要数百万计算单元的数值模型。因此，至少在可预见的未来，空气注入过程的数值模拟作为一种概念工具，在各地点仍将继续发挥重要作用，但其预测能力有限。
