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Three-dimensional numerical modeling of hydrodynamic flow, sediment deposition and transport in stormwater ponds and alluvial channels.

机译：雨水池塘和冲积河道水动力流动，泥沙沉积和运输的三维数值模拟。

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摘要

Prediction of flow and sediment transport is an important and challenging problem for stormwater management and river engineering applications. This thesis concerns primarily the computation of flow, sediment deposition and transport processes in stormwater ponds and alluvial channels based on a multiphase flow approach in modeling sediment transport. Starting from an existing hydrodynamic Reynolds Averaged Navier-Stokes flow solver, numerical models are developed to predict flow, sediment deposition and transport under the FLUENT software package. Two types of sediment transport models are formulated to consider quantities of present sediment phase volume fractions: a Discrete Phase Model in a Lagrangian frame where the sediment phase occupies a low volume fraction and particle-particle interactions are neglected; a Eulerian two-phase model where each phase is considered as an interpenetrating continuum and particle-particle interactions are not neglegible. The model is capable to model sediment transport with high volume fractions.;The solution methodologies are implemented numerically for different case studies. The Discrete Phase Model approach, together with a standard k -- epsilon turbulence model, is applied to stormwater pond modeling studies. The use of computational fluid dynamics to simulate flow fields and sediment depositions in stormwater tanks is beneficial because one may compare different factors that affect sedimentation efficiency. In particular, two case studies with different inlet and outlet pipes arrangements are investigated under different steady inflow conditions and bed boundary conditions. A method is employed and hooked to FLUENT for accurate simulations of particle settling behavior in stormwater ponds. The method considers critical bed shear stress as a threshold and evaluates local bed shear stress with this value to determine the particle deposition behavior. It is demonstrated that this model is an efficient 3D hydrodynamic flow and sediment transport numeric model for low sediment-laden flows, thus providing engineers and scientists with a useful tool for studying sediment deposition with a variety of sediment sizes, inflow conditions, and geometry arrangements.;In order to gain more insight into the fundamental flow and sediment interaction mechanics of sediment transport, an Eulerian two-phase model embeded in FLUENT is implemented in an open channel with loose bed based on two-phase mass and momentum equations. These equations are used in conjunction with the constitutive relations that are obtained by applying kinetic theory. Different from traditional sediment transport models, this model uses the two-phase theory, and thus, has no need to invoke any empirical sediment transport formulas. In this application, predictions for turbulent fluctuations for the fluid phase are obtained using a modified k -- epsilon turbulence model with a supplement of extra terms which take into account the interphase turbulent momentum transfer. Predictions for turbulent quantities for the solid phase are obtained using Tchen-theory correlations for the discrete particles under homogeneous and steady turbulent flows. Besides simulation of sediment transport, the model also provides some ideas for simulating scour and bed deformation. The results presented in this study demonstrate that the model is efficient and quite accurate in dealing with sediment transport and scour simulation with loose bed.
机译：对于雨水管理和河流工程应用，流量和泥沙输送的预测是一个重要且具有挑战性的问题。本论文主要涉及基于多相流方法模拟泥沙运移的雨水池塘和冲积河道的水流，泥沙沉积和输送过程的计算。从现有的流体动力学雷诺平均Navier-Stokes流量求解器开始，开发了数值模型，以在FLUENT软件包下预测流量，沉积物沉积和运输。制定了两种类型的沉积物传输模型来考虑当前沉积物相体积分数的数量：拉格朗日框架中的离散相模型，其中沉积物相占体积分数较低，而颗粒间的相互作用被忽略；一个欧拉两相模型，其中每个相都被视为一个互穿的连续体，粒子与粒子之间的相互作用不可忽略。该模型能够模拟高体积分数的泥沙运移。离散阶段模型方法与标准k-ε湍流模型一起被用于雨水池塘建模研究。使用计算流体动力学来模拟雨水箱中的流场和沉积物沉积是有益的，因为可以比较影响沉积效率的不同因素。特别是，在不同的稳定流入条件和床边界条件下，研究了两种采用不同进，出口管布置的案例研究。采用了一种方法并将其连接到FLUENT，以精确模拟雨水池塘中的颗粒沉降行为。该方法将临界床层切应力视为阈值，并使用该值评估局部床层切应力以确定颗粒沉积行为。结果表明，该模型是用于低含沙量的高效3D流体动力和泥沙运移数值模型，从而为工程师和科学家提供了研究各种沉积物尺寸，入流条件和几何布置的沉积物沉积的有用工具。为了更深入地了解泥沙输送的基本流动和泥沙相互作用机理，在两相质量和动量方程的基础上，在具有松散床的明渠中实现了嵌入FLUENT中的欧拉两相模型。这些方程式与通过应用动力学理论获得的本构关系结合使用。与传统的泥沙运移模型不同，该模型使用了两阶段理论，因此无需调用任何经验性的泥沙运移公式。在本申请中，使用修改后的k-ε湍流模型并考虑了相间湍流动量传递的额外项，获得了流体相湍流波动的预测。固相湍流量的预测是使用Tchen-理论相关性获得的，用于均匀和稳定湍流下离散颗粒的运动。除了模拟输沙，该模型还提供了一些模拟冲刷和床层变形的思路。在这项研究中提出的结果表明，该模型在处理沉积物和疏松冲刷模拟方面是有效且相当准确的。

著录项

  • 作者

    Zhang, Leying.;

  • 作者单位

    Old Dominion University.;

  • 授予单位 Old Dominion University.;
  • 学科 Engineering Environmental.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 121 p.
  • 总页数 121
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 环境污染及其防治;
  • 关键词

  • 入库时间 2022-08-17 11:38:26

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