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Study of pollutant transport in depth-averaged flows using random walk method

Journal of Hydrodynamics 2019年第2期31卷 303-316页

作者： Xue-fei Wu Dongfang Liang School of Environment and Resource Southwest University of Science and TechnologyMianyang 621010China Department of Engineering University of CambridgeCambridgeUK

The random walk particle tracking(RWPT)method is compared with the Eulerian methods in investigating pollutant transport in depth-averaged *** a typical representative of the Eulerian model with high performance,the MacCormack scheme with Total Variation Diminishing modification(TVD-Mac)is selected for *** concentration is simulated in four case ***,both numerical models have been tested in two idealized cases and compared against analytical *** dissipation is observed for TVD-Mac model where the concentration changes abruptly,especially under the circumstances of low resolution and misalignment between the flow direction and grid *** the contrary,simulations by the random walk model achieve higher accuracy in both cases and are free of fictitious oscillations in the vicinity of sharp concentration ***,the solute oscillation along a one-dimensional hypothetical tidal estuary is simulated,with the RWPT accurately con serving mass and suffering less rm merical diffusion compared with the Eulerian ***,the process of pollutant transport in a Yangzte River reach is predicted by the *** longitudinal dispersion coefficient DL is calculated *** is compared favorably with the theoretical/empirical formulae,indicating the validity of the RWPT in solving complex natural problems.

关键词： Pollutant transport depth-averaged flows random walk particle tracking TVD-MacCormack

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Comparison of depth-averaged concentration and bed load flux sediment transport models of dam-break flow

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Water Science and Engineering 2017年第4期10卷 287-294页

作者： Jia-heng Zhao Ilhan Ozgen Dong-fang Liang Reinhard Hinkelmann Department of Civil Engineering Technische Universitat BerlinBerlin 13355Germany Department of Engineering University of CambridgeCambridge CB2 1PZUK

This paper presents numerical simulations of dam-break flow over a movable bed. Two different mathematical models were compared: a fully coupled formulation of shallow water equations with erosion and deposition terms(a depth-averaged concentration flux model), and shallow water equations with a fully coupled Exner equation(a bed load flux model). Both models were discretized using the cell-centered finite volume method, and a second-order Godunov-type scheme was used to solve the equations. The numerical flux was calculated using a Harten, Lax, and van Leer approximate Riemann solver with the contact wave restored(HLLC). A novel slope source term treatment that considers the density change was introduced to the depth-averaged concentration flux model to obtain higher-order accuracy. A source term that accounts for the sediment flux was added to the bed load flux model to reflect the influence of sediment movement on the momentum of the water. In a onedimensional test case, a sensitivity study on different model parameters was carried out. For the depth-averaged concentration flux model,Manning's coefficient and sediment porosity values showed an almost linear relationship with the bottom change, and for the bed load flux model, the sediment porosity was identified as the most sensitive parameter. The capabilities and limitations of both model concepts are demonstrated in a benchmark experimental test case dealing with dam-break flow over variable bed topography.

关键词： Shallow water Sediment transport Bed load flux model depth-averaged concentration flux model Dam break

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Computing depth-averaged Flows Using Boundary-fitted Coordinates and Staggered Grids

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Tsinghua Science and Technology 2000年第2期5卷 226-230页

作者：洪益平周雪漪陈永灿余常昭 Department of Hydraulic and Hydropower Engineering Tsinghua University Beijing 100084 China

A depth averaged nonlinear k ε model for turbulent flows in complex geometries has been developed in a boundary fitted coordinate system. The SIMPLEC procedure is used to develop an economical discrete method for staggered grids to analyze flows in a 90° bend. This paper describes how to change a program in rectangular coordinate into a boundary fitted coordinate. The results compare well with experimental data for flow in a meandering channel showing the efficiency of the model and the discrete method.

关键词： depth-averaged k-ε model boundary-fitted coordinates staggered grid meandering channel

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Effects of vegetation patch density on flow velocity characteristics in an open channel

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Journal of Hydrodynamics 2019年第5期31卷 1052-1059页

作者： Wen-qi Li Dan Wang Jun-li Jiao Ke-jun Yang State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan UniversityChengdu 610065China

The aquatic plants are often found in natural rivers,and they affect the channel flow structure *** study the effects of the vegetation density a(the frontal area per volume)on the flow velocity characteristics,rigid bamboo circular cylinders are chosen as the model emergent *** the experiments,the density of the vegetation takes various values while all other flow parameters are kept constant.A 3-D acoustic Doppler velocimeter(ADV)is used to measure the local flow velocities for different vegetation *** results show that the existence of the vegetation patch leads to an increase of the depth-averaged velocity on the right and left sides behind the vegetation patch,and it increases monotonically with the vegetation *** different vegetation densities,the lateral distribution of the stream-wise velocity behind the vegetation patch follows approximately an S-shaped profile when a≤60 m-1,and a logarithmic profile if a>60 *** vertical distribution of the stream-wise velocity along the channel varies with the vegetation density and also follows an S-shaped distribution in a certain range,with the locations and the ranges being affected by the vegetation density.

关键词： Vegetation density stream-wise velocity depth-averaged velocity lateral distribution longitudinal distribution open channel

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Numerical simulation of transport and dispersion of side-discharged sewage in tidal flow

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Acta Oceanologica Sinica 2000年第2期19卷 137-144页

作者： Liang Shuxiu1 Shen Yongming1 Sun Zhaochen1 Ni Haoqing2 (1. State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China 2. China Institute of Water Resources Hydropower Research, Beijing 100044, China Key Lab. of Coast. and Offsh. Eng. Dalian University of Technology Dalian 116024 China

Based on N - S equations, the depth-averaged stress - flux algebraic model is used to simu late the anisotropic transport and dispersion when hot water or pollutants are side-discharged into large water they. In this model the depth-averaged continuity, momentum and concentration equations are employed, and the tide is asymmetric. The results show the changes of velocity field and pollutant con centration with time and space during one tidal period.

关键词： depth-averaged stress - flux algebraic anisotropy asymmetric tide

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