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西南交通大学学报 2011年第6期46卷 973-978页

作者：彭道平黄涛 aaron packman 西南交通大学地球科学与环境工程学院四川成都610031 美国西北大学土木与环境工程系伊利诺伊州埃文斯顿60208

为观测砷沉积导致的孔隙介质内部结构的改变,采用X射线差异微断层扫描技术,扫描从Loa流域获得的河床沉积物和实验室配制的含砷样品,对含砷聚集物在孔隙介质中的分布进行了成像分析.经过图像处理去除图像上的噪点和增强图像中砷的信息,... 详细信息

为观测砷沉积导致的孔隙介质内部结构的改变,采用X射线差异微断层扫描技术,扫描从Loa流域获得的河床沉积物和实验室配制的含砷样品,对含砷聚集物在孔隙介质中的分布进行了成像分析.经过图像处理去除图像上的噪点和增强图像中砷的信息,获得了孔隙介质中含砷聚集物的三维数据组;采用Avizo 6和Blob3D等工具,对三维数据组进行重建和可视化.成像显示:大量含砷聚集物沉积在介质孔隙和介质表面;不同尺寸聚集物的形态呈现出明显的多样化特征———小颗粒聚集物趋于球形,大颗粒聚集物则趋于扁平状.研究表明,该技术可在不破坏样品的前提下,实现对孔隙介质沉积前后内部结构变化的直接观测.

关键词：孔隙介质 X射线差异微断层扫描技术砷图像处理三维成像

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Application of Hausdorff fractal derivative to the determination of the vertical sediment concentration distribution

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International Journal of Sediment Research 2023年第1期38卷 12-23页

作者： Hongguang Sun Shiqian Nie aaron I.packman Yong Zhang Dong Chen Chengpeng Lu Chunmiao Zheng State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai University College of Mechanics and Materials Hohai University College of Mathematics and Systems Science Shandong University of Science and Technology Department of Civil and Environmental Engineering Northwestern University Department of Geological Sciences University of Alabama Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences College of Hydrology and Water Resources Hohai University School of Environmental Science and Engineering Southern University of Science and Technology

The Rouse formula and its variants have been widely used to calculate the steady-state vertical concentration distribution for suspended sediment in steady sediment-laden flows, where the diffusive flux is assumed to be Fickian. Turbulent flow, however, exhibits fractal properties, leading to non-Fickian diffusive flux for sediment particles. To characterize non-Fickian dynamics of suspended sediment, the current study proposes a Hausdorff fractal derivative based advection-dispersion equation(HADE)model, where the Fickian diffusive flux in the Rouse model is replaced by a fractal derivative re-scaled using a constant diffusivity. The order of the Hausdorff fractal derivative is designed to characterize the influence of the multi-fractal turbulence structure on sediment diffusion. Applications show that the HADE model, with the analytical solution expressed using a stretched exponential function, can accurately describe the observed vertical concentration profiles for suspended sediment with different *** improvement well captures the non-exponential decay of the vertical sediment concentration in turbulent flow. Further analyses of measured sediment concentration profiles reveal that the Hausdorff fractal order decreases with the Rouse parameter, which describes the stronger impact of turbulent flow and a more uniform sediment concentration profile for smaller particles. Model comparisons also show that the HADE model provides better performance in describing the sediment concentration profiles than the improved Rouse formula and the standard fractional derivative advection-dispersion equation(FADE), which either under-or over-estimates vertical displacement of sediment particles, likely due to coherent turbulent structures.

关键词： Anomalous diffusion Hausdorff fractal derivative Vertical concentration distribution Suspended sediment Metric transform

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STREAM-SUBSURFACE EXCHANGE, SUSPENDED SEDIMENT TRANSPORT, AND THE COUPLED TRANSPORT OF COLLOIDS AND CONTAMINANTS IN SEDIMENT BEDS

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International Journal of Sediment Research 2003年第2期 199-207页

作者： Jianhong REN ,aaron I. packman Department of Civil and Environmental Engineering Northwestern University Evanston IL USA

Recent interest in the role of sediments in contaminant transport and stream ecology has motivated additional study of both stream-subsurface exchange flows and suspended sediment transport, deposition, and resuspension. Detailed consideration of the hydrodynamic coupling of stream and pore water flows indicates that there will often be a considerable exchange flux between streams and porous stream beds. As a result, suspended sediments are readily carried from the stream into the subsurface where they can deposit due to physico-chemical interactions with the bed sediments. These processes can greatly influence the transport of fine sediments in streams, and also have important implications for the transport and fate of contaminants. Stream-subsurface exchange allows contaminants to interact with streambed sediments, and contaminants such as metals can sorb to colloidal phases, so that contaminant fate also depends to a large extent on the fate of the suspended sediments. Various degrees of interaction between colloids, contaminants, and stream bed sediments can result in a wide range of transport behavior. In addition, contaminant-particle and particle-particle interactions both depend on the background water chemistry (e.g., pH and ionic strength). Fundamental understanding of the underlying processes allows prediction of the coupled transport of suspended sediments and contaminants. These problems have been analyzed by combining fundamental fluid mechanics with appropriate chemical or physico-chemical interactions between contaminants, colloids, and bed sediments. Long-term modeling of fine sediment and contaminant transport in streams will require consideration of dynamic interactions between stream-subsurface exchange hydrodynamics and fine particle transport.

关键词： Stream hydraulics Suspended sediment transport Contaminant transport Hyporheic exchange

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