冲积河流混合活动层内床沙级配变化的动力学基本方程

本文将冲积河流混合活动层内床沙的交换、掺混概括为表层床沙与水中运动泥沙在床面附近湍流作用下的掺混交换和混合活动层中泥沙在沙波运动作用下的掺混交换过程，建立了冲积河流混合活动层内床沙级配变化的基本方程。该方程定量地反映了水流强度、床面沙波运动及河床冲淤变化与床沙级配变化的关系，描述了河床冲淤过程中床沙级配时空变化的动力学特性。文中还应用该方程，分析了河床冲刷粗化现象。     

悬移质水流挟沙能力与输沙特性

悬移质水流挟沙能力与输沙特性对于冲积河流泥沙冲淤、河床演变影响很大。作者在对我国广泛应用的悬移质挟沙力半经验性公式进行分析基础上，指出了这类公式应用的局限性，并通过试验研究提出了悬移质水流挟沙能力的新关系式，同时对输沙平衡时的临界不淤流速及临界坡降等表达式进行了探讨，文中结论的应用限于S=2-40kg/m^3中低含沙量的情况。     

冲积河流长距离冲刷不平衡输沙过程初步研究

本文从悬移质扩散方程出发, 研究冲积河流长距离冲刷不平衡输沙过程. 对于天然沙质河流, 床沙均为非均匀沙, 由于较细泥沙的冲刷率总大于较粗泥沙, 因此在床面薄层内泥沙随冲刷迅速粗比, 致使挟沙力降低, 不平衡输沙距离比均匀沙情况大大延长. 文中同时提出了表层床沙粗化的概化计算模式及床沙交换速率计算公式. 床沙交换速率的大小是决定含沙量恢复饱和距离的重要因素. 本文对不同类型底部边界条件进行了计算比较, 并与黄河下游的实际冲刷资料进行了对比, 结果表明, 应用梯度型底部边界条件, 且在考虑表层床沙粗化中以作者提出的公式计算床沙交换速率, 则计算含沙量和实际符合良好.     

沙质河床清水冲刷粗化的研究

研究了沙质河床清水冲刷粗化机理，即它不是靠推移质冲刷，而主要是靠悬移质冲刷，在粗化过程中产生沙波，形成与水和条件相适应的稳定的沙波运动，建立新的平衡。据此，提出了河质河床粗化物理模式和计算方法。     

基于输沙平衡度的河型成因理论假说及其验证

在建立冲积河流输沙平衡度公式的基础上,提出河型成因理论假说:冲积河流河型形成的内在成因是河流的输沙平衡度,外在成因是表达河床、水流和泥沙的物理量;河流系统中包含了河床系统、水流系统和泥沙系统3个二级系统;河道整治工程首先影响河型的外在成因,然后通过外在成因影响内在成因,不同的输沙平衡度过程形成了不同的河型。黄河下游的验证结果表明:依据冲积河流河型成因理论假说可以对河型进行分类,并有效地对河型进行预测,从理论上讲可以控制河型。     

天然河流沙质河床上器测推移质输沙率含义的商榷

作者基于天然河流沙质河床上的推移质和悬移质两类运动形式的泥沙,不存在一个能够截然划分的界面,认为在沙质河床上利用推移质采样器实测的推移质输沙率,其组成不都是推移质泥沙,其中尚包括悬移质中的床沙质泥沙。为此,本文分析了长江中游干流宜昌和汉口水文站河段利用推移质采样器实测的推移质输沙率和与之相应测次的、按测时水沙条件计算的临底流层内悬移质中床沙质泥沙输沙率的相关关系,论证了沙质河床上器测推移质输沙率中推移质泥沙和悬移质中床沙质泥沙组成的机理。     

冲积河道冲刷过程中横向展宽的初步模拟

本文首先描述了冲积河道横向展宽现象，分析了河岸横向冲刷、崩塌的机理及展 宽原因。然后建立细沙河流一维非均匀悬移质泥沙数学模型，同时结合河道横向展宽模式，预测冲积河道冲刷过程中，粘性土组成的河岸的横向展宽过程。此外，还分析了不同来水来沙条件及河岸土体特性对河道横向展宽和河床冲刷的影响，指出了影响冲积河道横向展宽的主要因素。     

沙质河床推移质输沙率计算研究

沙质河床推移质输沙计算无论在河流动力学的基本理论研究,还是在工程应用方面都有重要意义。本文回顾了前人主要研究成果,认为因推移质输沙率测验精度低而使现有公式多不适用于典型沙质河床,故在阐明推移质与悬移质泥沙交换运动机理基础上,借助因测验精度较高而在学科研究较成熟的悬移质含沙量垂线分布公式,通过向河底外延推求出推移质泥沙输沙率,并充分考虑泥沙粒径、水流强度及水力摩阻特性对沙质推移质输沙厚度的影响,得到了物理概念清晰、形式较为简明的沙质推移质输沙率公式。通过黄河细沙河床实测资料验证结果表明,本文建立的公式比前人推移质输沙率公式具有较高计算精度,可以应用到推移质输沙率测验精度不能保证的沙质河段的河床变形计算。     

潮汐河口平面二维悬沙输移及河床变形的数值模拟

本文应用平面二维非恒定水流运动方程和悬移质不平衡输沙方程，针对不同物理量的特性，采用不规则网格的差分法求解水流运动方程和有限控制体积法求解悬移质泥沙输移方程。利用杭州湾水文泥沙实测资料对模型进行了验证，所得结果是满意的。     

河道冲刷和清水水流河床冲刷率

在冲积河流里。水流条件变化如洪水、水库泄放清水、河道渠化等使挟沙力不饱和引起冲刷，称为河道冲刷。这与水工建筑造成的局部冲刷不同。河道冲刷深度主要决定于冲刷率和冲刷历时。本研究通过对各种泥沙大量实验，证明了河床冲刷率正比于水流提供的冲刷功率并依赖于泥沙粒径和容重，首次提出了冲刷率公式。经验证，该公式可以用于非恒定流输沙和河流洪水冲刷计算。     

悬移质近底参考面平衡浓度的一个计算公式--对Lane与Kalinske模式的改进

根据推移质与床沙交换、悬移质主要与推移质交换的物理背景，采用Einstein床面泥沙的起动概念及推移运动概率函数表征床面泥沙起动及推移运动，采用Lane与Kalinske提出的泥沙因水流垂向脉动而进入悬浮运动的模式表征推移质进入悬浮运动的过程，建议一个床面层高度，建立了一个悬移质近底平衡浓度的一个计算公式。公式的参数由实测资料确定，公式经过了独立资料的检验，计算精度在可以接受的范围内。基于本文建议的床面层高度及参考面平衡浓度公式，建立了悬移质输沙率计算方法，取得了满意的输沙率计算精度。对于细颗粒泥沙的悬移质输沙率计算，本文公式克服了Einstein方法的缺陷。     

河流水冰沙耦合模型研究Ⅱ：验证与应用

北方河流冬季河冰运动会带来凌汛灾害威胁,研究流凌运动对水流、泥沙和河道的影响具有重要工程意义。本文在平面二维河冰动力学模型基础上,建立二维水冰沙耦合数值模型。基于三角形的非结构网格,采用具有迎风特性的Petrov-Galerkin型有限元法计算非恒定水流过程、非恒定非均匀沙输运和河床冲淤变化,利用无网格的SPH法计算河冰运动,基于河冰对岸滩的刮擦切应力计算岸坡侵蚀,再利用双泥沙休止角法分析不同含水层岸坡的稳定坡面。该模型创新性地耦合水沙理论和河冰理论,能模拟北方河流全季节及河冰全过程的水位流量波动、河冰运动、泥沙输移、河床冲淤及岸滩崩塌过程。通过实验条件下溃坝引起的岸坡崩塌侵蚀验证了模型的准确性和可靠性,研究结果显示该模型能再现水流、河冰、泥沙、河床及河岸间的复杂耦合作用,揭示河冰刮擦对岸滩侵蚀破坏的促进机理,可进一步支撑冬季河道防凌减灾和岸滩水土保持研究。     

Experimental study on the bed topography evolution in alluvial meandering rivers with various sinuousnesses

The bed morphology in alluvial meandering rivers is composed of both alternatively distributed free bars and curvature related point bars. To study the influence of channel sinuousness on the flow and sediment transport, and consequently the bed morphology in meandering rivers, experiments were carried out in a series of curved channels with erodible bed fixed side walls. Measurements on the surface flow field, bed topography evolution and sediment transport rate were performed. Experimental results show a high velocity area near convex bank at a streamwise position a little bit upstream of the apex and the increasing in sinuousness of channel tends to increase the cross-sectional variation of flow velocity at the apex of bends. Point bars and pools appear in the channel bends in all experimental runs the bedform has an obvious tendency of downstream migration as a whole. The quasi-equilibrium bedform in the channel bends are dominated by two independent factors: the influence of curvature and the influence of flow-bed instability inside the channel. The increasing of flow rate leads to a faster development of bars and pools, as well as faster downstream migration of the entire bedform. The increase of sinuousness in channel bends leads to the increase of both the spatial and the temporal fluctuation of bedforms. Bedload is dominant in the sediment transport and the sediment transport rate tends to increase with the increasing of the inlet flow rate but decrease with the increasing of the channel sinuousness. Computational results on the bed topography in river bends was also presented based on empirical models, showing that the highly sinuous channels have more uncertainty in bed morphology and more difficult to be predicted with mathematical models when compared with slightly sinuous channel bends. The coupled interaction of point bars, mid-channel bars, alternative bars and even sand ripples are thought to complicate the mechanism and make the bed morphology difficult to predict. The experiment results can be useful for further theoretical study on the dynamics of river meanders with water depth-width ratio as small as 1/10 to 1/20 and bedload dominated sediment transport.     

冲积河流沙质河床推移质级配分布规律

推移质级配是进行推移质输沙率、河床冲淤等计算模拟的重要条件。本文从分析沙质河床近壁紊动源区内泥沙运动临界图景入手,运用瞬时动量对撞平衡原理得到推移质泥沙临界运动条件,并基于垂向瞬时紊动速度所具有的高斯分布规律,求解随机方程,建立了理论性较强的沙质河床推移质颗粒级配计算公式。黄河与长江的实测资料检验结果表明,本文提出的公式能同天然沙质河床推移质实测资料符合,因而对于确定冲积河流沙质河床推移质泥沙级配具有重要的理论意义和实用价值。     

水库下游冲刷的数值模拟—模型的构造

由于水库下游冲刷过程中悬移质与推移质、推移质与河床质、河床质与悬移质交换机理及床沙粗化机理的复杂性,使得研究水库下游冲刷数学模型的难度较大。 为了研究水库下游冲刷、河床演变问题及由此而引起的对防洪、航运等造成的影响,本文建立了一维全沙数学模型,模型考虑了非均匀悬移质不饱和输移、非均匀沙推移质输移及床沙级配的调整。文中考虑了冲刷过程中挟沙能力的沿程调整,挟沙能力包括以下三个方面,即悬移质中细颗粒部分从累计效果看不参予与床沙交换(冲泻质),这部分泥沙全部计入挟沙能力;悬移质的粗颗粒部分落淤到床面与床沙交换后部分地计入挟沙能力;床沙中可悬浮部分从床面冲起后部分地计入挟沙能力。非均匀沙推移质输沙率公式考虑了床沙运动的随机性及床沙粗化对输沙率的影响。床沙级配的调整采用CARICHAR混合层模型。对计算中经常遇到的关键性问题提出了处理方法。     

Estimating Sediment Budget at a River Basin Scale Using a Process-Based Distributed Modelling Approach

The paper presents a process-based distributed modelling approach for estimating sediment budget at a river basin scale with partitions of suspended and bed loads by simulating sediment loads and their interactions. In this approach, a river basin is represented by hillslopes and a network of channels. Hillslopes are divided into an array of homogeneous grid cells for modelling surface runoff and suspended sediments. Channels are defined by incorporating flow hydraulic properties into the respective hillslope grids as sub-grid attributes for modelling both suspended and bed loads. Suspended sediment transport is modelled using one dimensional kinematic wave approximation of Saint-Venant’s principles of conservation of mass and momentum. Transport capacity of runoff or streamflow is used to set the limit of suspended sediment transport rate. Bed load in channels is estimated based on the instantaneous water and hydraulic parameters. Fractional interchange between suspended load and bed load is then back calculated. The performance of the model was evaluated through a case study application in a large river basin in Japan. The model satisfactorily calculated the sediment transport and total sediment budget in the basin. The simulated bed load was found to be reasonable and consistent with the water flow and suspended sediment flux. The results showed the bed load can be expressed as a linear function of the suspended load. The fractions of different sediment loads also exhibit linear relationships with water discharge for the rising and recession limbs of the flood hydrographs. The case study has demonstrated that the process-based distributed modelling approach can efficiently describe the basin-scale sediment budgets with due consideration of the suspended and bed loads and their interactions in the hillslopes and channels.     

Two Dimensional Heavy Metal Transport Model for Natural Watercourses

This work presents the development and calibration of a two‐dimensional (depth‐averaged) river flow, sediment transport and heavy metal transport model in natural watercourses. Because heavy metals occur in dissolved and adsorbed phases, implementing the active‐layer concept for sediment transport computation enabled the development of a heavy metal transport model that accounts for pollutant moving in dissolved phase, adsorbed on suspended sediment, adsorbed on bed‐load, deposited in the active‐layer of the river bed or adsorbed on sediment in deeper strata. The proposed concept also enables the modelling of pollutant exchange processes using accessible sediment particle surface area for suspended and bed sediment separately. The presented heavy metal transport model is able to manage sediment mixtures found in natural watercourses using an arbitrary number of sediment size‐classes, distinguishing in this way smaller size‐classes that engage in interaction with the pollutant. Using field measurements for a reach of the Danube River, simulations were conducted for water flow, sediment transport and heavy metal transport. While some discrepancies between measured and computed values for pollutant concentrations were observed, the model reproduced the water and sediment contamination quite reasonably with acceptable mass conservation errors. The simulations also gave an insight in the general behaviour of the monitored heavy metals in the considered river reach. Therefore, it can be concluded that the developed model is suitable for simulating complex flow, sediment transport and heavy metal transport conditions in natural watercourses. Copyright © 2015 John Wiley & Sons, Ltd.     

一维河网非恒定流及悬沙数学模型的节点控制方法

本文的一维河网非恒定流及悬沙数学模型，是根据以一维圣维南方程组，悬沙非平衡输运方程及水位、含沙量节点控制法而建立。首先，利用单一河流有限差分方程组转换形式和节点处质量、能量守恒性，写出所有节点的水位控制方程组。求解此不规则稀疏矩阵方程组得到得有节点的水位，再由单一河流非恒定流的求解方法可获得所有单一河流的断面水位和流量。基于水注的节点水位控制法，本文提出了节点悬沙控制法。假设节点处冲刷或淤积较小，所有节点的含沙量控制方程组可通过输沙量守恒方程用矩阵形式写出。求解此不规则稀疏矩阵方程组，得到所有节点处的含沙量。所有单一河流断面处的含沙量通过单一河流悬沙输运的求解方法获得。本文介绍的模型适用于各种河网类型。作为检验，该模型成功地应用于珠江三角洲流域河网水流及悬沙的数值计算。