Incipient Velocity of Non-uniform Sediment in Sloping River Bends

A model for incipient movement of sediment in rolling pattern was established. In this model, the starting of sediment particles under low transport rate, the exposure degree of sediment, the lateral slope of water surface and the effect of transverse circulating current induced by the hydraulic structure of bend flow were fully considered. A theoretical formula for the incipient velocity of non-cohesive and non-uniform sediment in sloping river bends was developed. The results from the theoretical formula compared well with the experimental data.

Stability and self-adaption character of turbulence coherent structure in narrow-deep river bend

In a meandering fiver, a certain scale of turbulent vortex dominates the development of fiver morphology, making the river bend with s particular curvature. This kind of vortex is denoted as ＂bend-forming vortex＂. The coordinated relationship of bend-forming vortex and meandering fiver channel is then known as ＂self-adaption feature＂ of rivers. With these two concepts, this paper investigated the stability and self-adaption character of coherent vortex in the U-shape river bend with a constant curvature. On the basis of fluid mechanics theory and in consideration of turbulent coherent vortex as disturbance, the growth rate and the wave number response range of coherent vortex in meandering rivers with different curvatures were calculated in this paper. Moreover, the responses of different scales of coherent turbulence structure to river bend parameters were analyzed to explain the mechanism of fiver bend maintenance. These methods could provide a theoretical basis for further investigation on fiver meandering.

Tracer advection in an idealised river bend with groynes

This paper presents numerical simulations of particle advection in the bend of an open channel containing groynes, which is an idealised form of a shallow river bend in a wide river. The flow field is computed using a boundary-fitted solver of the non-orthogonal, curvilinear shallow water equations. The computational grid is generated by solving Poisson-type elliptic partial differential equations using an iterative multi-grid scheme for prescribed boundary coordinates. The shallow water equations are discretised with finite differences in space, and 4 t h order Runge-Kutta integration in time. Tracers introduced at specific initial locations have their trajectories computed using Lagrangian particle tracking. The numerical shallow flow model is verified by comparison to the analytical solution of fully developed flow in an open channel. The combined shallow flow and Lagrangian particle-tracking model is then used to simulate the advection of tracer particles in a rectangular channel containing a pair of parallel groynes, and tracer particles in a curved open channel containing groynes, of dimensions roughly equivalent to a Danube River bend.

Just Around the River Bend

China vows to stimulate business and development in the stagnant Tumen River region to expand trade into northeast

Numerical modeling of flow in continuous bends from Daliushu to Shapotou in Yellow River

The upper reach of the Yellow River from Daliushu to Shapotou consists of five bends and has complex topography. A two-dimensional Re-Normalisation Group （RNG） k-ε model was developed to simulate the flow in the reach. In order to take the circulation currents in the bends into account, the momentum equations were improved by adding an additional source term. Comparison of the numerical simulation with field measurements indicates that the improved two-dimensional depth-averaged RNG k-e model can improve the accuracy of the numerical simulation. A rapid adaptive algorithm was constructed, which can automatically adjust Manning＇s roughness coefficient in different parts of the study river reach. As a result, not only can the trial computation time be significantly shortened, but the accuracy of the numerical simulation can also be greatly improved. Comparison of the simulated and measured water surface slopes for four typical cases shows that the longitudinal and transverse slopes of the water surface increase with the average velocity upstream. In addition, comparison was made between the positions of the talweg and the main streamline, which coincide for most of the study river reach. However, deviations between the positions of the talweg and the main streamline were found at the junction of two bends, at the position where the river width suddenly decreases or increases.

A new conception on the formation of the first bend of Yangtze River: its relations with Eocene magmatic activities

Based on field observations, the author proposes a new understanding on the formation of the first bend of the Yangtze River. The relationship between the formation of the first bend of the Yangtze River and Eocene magmatic activity is expounded, suggesting that the first bend of the Yangtze River is the result from choking of the strong magmatic activity in Eocene. As a result, the upstream became a natural reservoir, whose riverside between Mt. Yulong and Mt. Haba was burst, guiding Jinshajiang River running eastward. At the same time, the drastic uplift of the Qinghai-Tibet Plateau led to the deep dissection of the river cut down the channel, resulting in the formation of the Tiger Leaping Gorge. The magnitude of uplift in the study area (located in the eastern of the Tibetan Plateau) is calculated. Taking Mt. Yulong as a base, the magnitude of lift is 3,300 m from Eocene to Pliocene, adding 700 m since Pleistocene, totaling up to 4,000 m or so.

An Analysis of Africans’ Blind Worship Towards European Culture in V. S. Naipaul’s A Bend in the River

As an important early work of Nobel laureate Naipaul and a model of postcolonial works,A Bend in the River has been studied for decades.It is not hard to find Africans’blind worship towards European culture after reading this book.This paper aims to explore the manifestations of Africans’blind worship towards European culture in the novel by a close reading and acts as a wake-up call for almost every nations existing in the age of globalization to firm their own national cultural stand and enhance cultural confidence so as to remain invincible in the unprecedented changes.

城镇化、技术创新影响全要素能源利用效率的中介效应研究——来自黄河“几”字弯的实证

采用全局参比Malmquist模型测算黄河“几”字弯都市圈城市2006—2021年的全要素能源利用效率,分析GML指数变化与全要素能源利用值的变化,利用三阶段中介效应模型分析城镇化、技术创新对黄河“几”字弯都市圈城市全要素能源利用效率的影响效应。研究表明:黄河“几”字弯大部分城市的全要素能源利用效率值呈现增长态势,且资源型城市高于非资源型城市,省会城市低于非省会城市;产业结构高级化是城镇化促进全要素能源利用效率的部分中介;经济增长是技术创新促进全要素能源利用效率的完全中介;降低环境污染是技术创新促进全要素能源利用效率的部分中介。黄河“几”字弯都市圈各城市应构建现代经济能源体系,加速产业升级与城市转型,建设低碳零碳负碳工程,推动技术创新与经济增长、绿色发展齐头并进。

急弯河段新建船闸上游引航道通航条件研究

在急弯河段已建枢纽上新建船闸工程,船闸布置受限因素众多,通航条件复杂。为分析船闸引航道通航水流条件,建立袁河石洲枢纽1:80正态物理模型,开展急弯河段船闸上游引航道通航水流条件试验,对比隔流堤不同长度口门区的流速分布,同时结合自航船模试验分析船闸口门区通航条件。结果表明,延长隔流堤对减小口门区横向流速峰值、改善流态作用明显;隔流堤延长250 m时,石洲船闸上游引航道最高通航流量可达到规范要求的20 a一遇洪水。

黄河“几”字弯都市圈资源环境承载力与经济发展耦合协调研究

在生态文明建设理念下,如何实现生态脆弱区资源环境与经济的协调发展,已成为我国亟待解决的问题之一。以典型生态脆弱区黄河“几”字弯都市圈21个地级市为例,基于2005年、2010年、2015年、2020年的资源环境与经济发展数据,运用熵权TOPSIS法分析资源环境承载力状况,并引入耦合协调度模型揭示资源环境承载力与经济发展水平耦合协调关系及其时空演变特征,结果表明:黄河“几”字弯都市圈资源环境承载力呈波动上升趋势,区域差异显著;资源环境承载力与经济发展水平的耦合协调度整体逐渐趋向于更高程度的耦合;通过莫兰指数分析发现,黄河“几”字弯都市圈资源环境承载力与经济发展水平耦合协调度为显著空间正相关。

巴基斯坦卡洛特水电站取水防沙试验研究

多沙河流上水电站取水发电,泥沙问题是需要解决的关键问题。本文通过物理模型试验,研究了巴基斯坦卡洛特水电站泥沙淤积发展规律。结果表明:通过“分级相机拉沙”排沙优化调度运行方式和“双重弯道分沙取水”枢纽布局,卡洛特水电站的淤积平衡年限延长至20年,坝上游8.15 km河段泥沙累积淤积量为4782.3万m^(3),平均淤厚27.4 m,最大淤厚51.7 m,兴利库容保留率78.56%;蓄水期,过机水流含沙量降低92.1%,汛前和汛后过机水流含沙量降低33.7%,全年通过电厂机组的水流含沙量不超过1.2 kg/m^(3),过机泥沙粒径原型值最大为0.02 mm,基本无粗沙过机问题。卡洛特水电站排沙调度方式和枢纽布局为解决高原地区多沙河流水电站泥沙问题提供了解决思路。

雅鲁藏布江大拐弯地区滑坡发育分布特征及其对地貌演化的响应

雅鲁藏布江大拐弯地区位于青藏高原东南部,是世界上地壳隆升和地貌演化最快的区域之一。在内外动力耦合作用下,区内滑坡灾害极其发育,严重制约着公路、铁路和水电工程的规划建设。本文以滑坡对地貌演化的响应为切入点,剖析了地形地貌、河流侵蚀、构造活动与滑坡分布的关系。研究表明:滑坡在地貌演化中扮演着重要角色,区内局部地形起伏度和坡度与滑坡发生呈非线性正相关关系,沟谷地貌通过增加斜坡陡度和滑坡率来适应的区域地壳隆升和河流快速下切;分析不同地貌演化阶段的面积-高程积分,随着地表侵蚀程度的增高,滑坡的面积比、滑坡坡度的平均值和中位数值都逐渐增大,表明滑坡侵蚀在区内快速侵蚀中起着重要支撑作用;河流侵蚀对滑坡的控制作用明显,雅鲁藏布江大拐弯在纵坡降较陡、河流功率大的加拉-金珠藏布口滑坡密集分布;滑坡发育与断裂密度呈正相关关系,与断裂距离呈负相关关系,区内断裂剧烈活动诱发的地震滑坡也是造成地貌侵蚀的重要媒介。研究结果有利于加深对雅鲁藏布江大拐弯地区滑坡孕灾背景的认识,也可为研究区的工程规划建设和防灾减灾提供科学依据。

被喂养的非洲——《大河湾》中的逆写帝国与生态批评

奈保尔的代表作《大河湾》描绘了民族解放运动后新兴的非洲国家面临的军事与经济危机,刻画当地的历史伤疤以及在现代化进程中面临的困境,揭示了殖民主义与帝国主义的本质。通过后殖民生态批评的视角审视该小说,不难发现西方霸权主义在经济全球化掩盖下给第三世界国家带来的惨重伤害。奈保尔强烈批判殖民主义与新殖民主义造成的自然生态的破坏、社会生态的紊乱与精神生态的崩溃,他试图打破人与自然的二元对立,建构三位一体的生态平衡。

Theoretical analyses on hydrodynamic instability in narrow deep river with variable curvature

Bending river is the most common river type in nature, and it is also a typical example for river evolution. The transform of the flow pattern can affect the development of the riverbed form. In return, the variation in the riverbed form can affect the hydrodynamic characteristics of the flow, thereby leading to the continuous evolution of the bending river. Based on this, a theoretical model for the bending river is established. The hydrodynamic instability characteristics of the laminar flow in the channel with a variable curvature, a typical and the variations of some parameters such wave frequency are also discussed. model as the meandering river, are studied, as the curvature, the wave number, and the

以系统观念构建陕西黄河“几字弯”生态治理格局

坚持系统观念,扎实推进山水林田湖草沙一体化保护和系统治理,是解决荒漠化综合防治攻坚难题,构建黄河“几字弯”生态治理新格局的重要工作方法和根本思维方式。以陕西黄河“几字弯”攻坚区为例,采用系统生态观分析陕西黄河“几字弯”沙化演变,强调系统观念在生态工程治理中的重要作用,实现了局部与整体、历史与现实、多元主体与综合措施、全局谋划与落地见效的有机统一。近二十年来,陕西黄河“几字弯”地区荒漠化和沙化治理成效显著,植被覆盖率显著提升。根据国家黄河“几字弯”攻坚战总体部署与“几字弯”的实际情况,制定了“三区三带”生态治理方案。该方案的提出,体现了系统智慧,为区域治理提供了新的思路和方法。

黄河“几字弯”沙化土地综合治理思路和举措探讨

黄河“几字弯”位于内蒙古中西部,范围涉及内蒙古7个盟市,具有重要的生态地位和战略地位。文章从四个方面分析了黄河“几字弯”面临的生态问题,针对存在的问题提出治理思路和六大具体治理举措,并就未来持续推进黄河“几字弯”沙化土地综合治理事业高质量发展提出建议。

河道形态重塑对城市河流污染物迁移扩散影响的数值模拟

以重庆市梁滩河某典型渠化河道(Urban)为例,采用RiverBuilder数值模拟工具将河道形态改造为6种河道,利用构建的二维水动力-对流扩散模型考察了河道形态重塑对河流水体更替时间(T_(TOT))、污染物浓度曲线(C_(CC))、污染物达到最大值时间(M_(MT))和污染物达到下游边界时间(A_(AT))等污染物迁移扩散指标的影响。结果表明,通过分别改变Urban河道的宽度(W_(bf))、深度(D_(bf))和蜿蜒度(Md)3个几何变量来重塑河道形态,虽可在一定程度上抑制污染物的迁移扩散,但效果不及基于变量D_(bf)进行多变量组合变化的复合河道。同时,近自然(Natural)河道的抗污能力及污染物扩散抑制能力最强,更适于河流污染物的自净过程。研究证实,将W_(bf)、D_(bf)、M_(d)进行无序复杂变化营造的河道形态更接近Natural河道,能为河流水体水质改善提供良好的生态水力条件。

基于高分辨率遥感影像的荆江河段南部洪道崩岸监测——以戥盘洲弯道为例

为研究长江支流崩岸情况,本文以荆江河段南部松滋河戥盘洲弯道及江心洲为例,利用高分辨率遥感影像数据,采用定量描述的方法,对其2013—2022年崩岸情况进行监测。监测结果表明,河道和江心洲都存在不同程度的崩岸,其中监测点南部河道宽度由2013年4月的203.11 m扩宽至2022年11月的287.94 m,平均每年扩宽8.5 m,每月扩宽0.74 m。5个监测点在监测期内都有不同程度的崩岸,崩岸程度最严重的监测点至河道岸边的距离从2013年4月的122.56 m缩短至2022年11月的60.13 m,平均每月缩短达0.54 m。因此,利用高分辨率遥感影像开展崩岸监测是一种非常有效的监测手段,是常规监测的有益补充;建议在开展长江主干流崩岸监测和修建防护工程的同时,应加强对长江支流河道崩岸的监测和河道防护。

基于IF-GEP的河湾最大冲刷深度预测方法

为解决传统河流流经弯道的最大冲刷深度预测过程中存在的不足,将孤立森林(IF)和基因表达式编程(GEP)方法相结合,建立了一个基于IF的GEP河湾最大冲刷深度预测模型(IF-GEP),并将该模型与传统GS-SVR和RF模型及现有经验公式进行对比。结果表明,IF-GEP预测模型在测试集上取得了较好的预测效果,且预测精度明显高于现有公式及传统的GS-SVR和RF模型。最后将该预测模型应用于多条不同河流的预测中,IF-GEP预测模型的预测结果与实际测量值较吻合,说明该预测模型具有良好的预测能力和较高的泛化性能。

黄河宁夏永丰渡口连续弯曲河段河床稳定性分析

河流连续弯道是大多数自然河流常见的特征,环流是弯道中最常见的要素之一,环流与纵向水流结合在一起,在弯道横断面内指向凹岸螺旋前进,对河流稳定性产生了复杂影响。因此,为研究连续弯曲河流中环流对河流水动力及泥沙输移的影响,利用声学多普勒剖面仪、激光粒度分布仪、GPS-RTK等实验仪器,对黄河宁夏永丰渡口连续弯曲河道水动力学要素进行了比较分析。结果表明:经长期冲淤,河床断面形式与弯道内环流存在关系,环流会构造河床断面的形状,改变水流主流线的方向,使其发生摆动;在连续弯道内,影响含沙量的主要因素是流速,二者呈正相关关系;相比于直线段,弯曲河道稳定性更差,更易发生河床变形。