School of Resources and Environmental Engineering, Hefei University of Technology, Hefei, 230009, China.
School of Resources and Environmental Engineering, Hefei University of Technology, Hefei, 230009, China.
Chemosphere. 2023 Sep;334:139013. doi: 10.1016/j.chemosphere.2023.139013. Epub 2023 May 22.
Understanding high-velocity pollutant transport dependent on the large hydraulic gradient and/or heterogeneity of the aquifer and criteria for the onset of post-Darcy flow have attracted considerable attention in water resources and environmental engineering applications. In this study, a parameterized model is established based on the equivalent hydraulic gradient (EHG) which affected by spatial nonlocality of nonlinear head distribution due to the inhomogeneity at a wide range of scales. Two parameters relevant to the spatially non-local effect were selected to predict the development of post-Darcy flow. Over 510 sets of laboratory one-dimensional (1-D) steady hydraulic experimental data were used to validate the performance of this parameterized EHG model. The results show that (1) the spatial nonlocal effect of the whole upstream is related to the mean grain size of the medium, and the anomalous variation due to the small grain size implies the existence of the particle size threshold. (2) The parameterized EHG model can effectively capture the nonlinear trend that fails to be described by the traditional local form of nonlinear models, even if the specific discharge stabilizes at the later stages. (3) The Sub-Darcy flow distinguished by the parameterized EHG model can be equated to the post-Darcy flow, and then the criteria for the post-Darcy flow will be strictly distinguished under the premise of determining the hydraulic conductivity. The results of this study facilitate the identification and prediction of high-velocity non-Darcian flow in wastewater management and provide insight into mass transport by advection at the fine-scale.
理解依赖于大水力梯度和/或含水层非均质性的高速污染物迁移以及达西流后发生的准则，在水资源和环境工程应用中引起了相当大的关注。在这项研究中，建立了一个基于等效水力梯度（EHG）的参数化模型，该模型受非线性水头分布空间非局部性的影响，这种非局部性是由于大范围尺度上的非均质性引起的。选择了两个与空间非局部效应相关的参数来预测达西流后的发展。使用了超过 510 组实验室一维（1-D）稳态水力实验数据来验证这个参数化 EHG 模型的性能。结果表明：（1）整个上游的空间非局部效应与介质的平均粒径有关，而由于小粒径引起的异常变化意味着存在粒径阈值。（2）参数化 EHG 模型可以有效地捕捉传统非线性模型的局部形式无法描述的非线性趋势，即使在后期阶段比流量稳定。（3）参数化 EHG 模型区分的亚达西流可以等同于达西流后，然后在确定水力传导率的前提下，可以严格区分达西流后的准则。本研究的结果有助于识别和预测废水管理中的高速非达西流，并深入了解细尺度上的对流质量传输。
