Numerical Simulation of Bed Load and Suspended Load Sediment Transport Using Well-Balanced Numerical Schemes

Sediment transport can be modelled using hydrodynamic models based on shallow water equations coupled with the sediment concentration conservation equation and the bed con-servation equation.The complete system of equations is made up of the energy balance law and the Exner equations.The numerical solution for this complete system is done in a seg-regated manner.First,the hyperbolic part of the system of balance laws is solved using a finite volume scheme.Three ways to compute the numerical flux have been considered,the Q-scheme of van Leer,the HLLCS approximate Riemann solver,and the last one takes into account the presence of non-conservative products in the model.The discretisation of the source terms is carried out according to the numerical flux chosen.In the second stage,the bed conservation equation is solved by using the approximation computed for the system of balance laws.The numerical schemes have been validated making comparisons between the obtained numerical results and the experimental data for some physical experiments.The numerical results show a good agreement with the experimental data.

Local vs. cross station simulation of suspended sediment load in successive hydrometric stations: heuristic modeling approach

The present paper aims at modeling suspended sediment load(SSL) using heuristic data driven methodologies, e.g. Gene Expression Programming(GEP) and Support Vector Machine(SVM) in three successive hydrometric stations of Housatonic River in U.S. The simulations were carried out through local and cross-station data management scenarios to investigate the interrelations between the SSL values of upstream/downstream stations. The available scenarios were applied to predict SSL values using GEP to obtain the best models. Then, the best models were predicted by SVM approach and the obtained results were compared with those of GEP. The comparison of the results revealed that the SVM technique is more capable than the GEP for modeling the SSL through the both local and cross-station data management strategies. Besides, local application seems to be better than cross-station application for modeling SSL. Nevertheless, the cross-station application demonstrated to be a valid methodology for simulating SSL, which would be of interest for the stations with lack of observational data. Also, the prediction capability of conventional Sediment Rating Curve(SRC) method was compared with those of GEPand SVM techniques. The obtained results revealed the superiority of GEP and SVM-based models over the traditional SRC technique in the studied stations.

Seasonal distribution and relationship of water mass and suspended load in North Yellow Sea

The concentration of suspended load can be determined by its linear relationship to turbidity.Our results present the basic distribution of suspended load in North Yellow Sea.In summer,the suspended load concentration is high along the coast and low in the center of the sea.There are four regions of high concentration in the surface layer:Penglai and Chengshantou along the north of the Shandong Peninsula,and the coastal areas of Lüshun and Changshan Islands.There is a 2 mg/L contour at 124°E that separates the North Yellow Sea from regions of lower concentrations in the open sea to the west.And there is a 2 mg/L contour at 124°E that separates the North Yellow Sea from regions of lower concentrations in the open sea to the west.The distribution features in the 10 m and bottom layer are similar to the surface layer,however,the suspended load concentration declines in the 10 m layer while it increases in the bottom layer.And in the bottom layer there is a low suspended load concentration water mass at the region south of 38°N and east of 123°E extending to the southeast.In general,the lowest suspended load concentration in a vertical profile is at a depth of 10 to 20 m,the highest suspended load concentration is in the bottom near Chengshantou area.In winter,the distribution of suspended load is similar to summer,but the average concentrations are three times higher.There are two tongue-shaped high suspended load concentration belt,one occurring from surface to seafloor,extends to the north near Chengshantou and the other invades north to south along the east margin of Dalian Bay.They separate the low suspended load concentration water masses in the center of North Yellow Sea into east and west parts.Vertical distribution is quite uniform in the whole North Yellow Sea because of the cooling effect and strong northeast winds.The distribution of suspended load has a very close relationship to the current circulation and wind-induced waves in the North Yellow Sea.Because of this,we have been able to show for the first time that the distribution of suspended load can be used to identify water masses.

Daily and Monthly Suspended Sediment Load Predictions Using Wavelet Based Artificial Intelligence Approaches

In the current study, the efficiency of Wavelet-based Least Square Support Vector Machine(WLSSVM) model was examined for prediction of daily and monthly Suspended Sediment Load(SSL) of the Mississippi River. For this purpose, in the first step, SSL was predicted via ad hoc LSSVM and Artificial Neural Network(ANN) models; then,streamflow and SSL data were decomposed into subsignals via wavelet, and these decomposed sub-time series were imposed to LSSVM and ANN to simulate discharge-SSL relationship. Finally, the ability of WLSSVM was compared with other models in multistep-ahead SSL predictions. The results showed that in daily SSL prediction, LSSVM has better outcomes with Determination Coefficient(DC)=0.92 than ad hoc ANN with DC=0.88. However unlike daily SSL, in monthly modeling, ANN has a bit accurate upshot.WLSSVM and wavelet-based ANN(WANN) models showed same consequences in daily and different in monthly SSL predictions, and adding wavelet led to more accuracy of LSSVM and ANN. Furthermore,conjunction of wavelet to LSSVM and ANN evaluated via multi-step-ahead SSL predictions and, e.g.,DC LSSVM=0.4 was increased to the DC WLSSVM=0.71 in 7-day ahead SSL prediction. In addition, WLSSVM outperformed WANN by increment of time horizon prediction.

A DISCUSSION ON CURRENTS AND SUSPENDED LOAD TRANSPORT IN SURF ZONE

In this paper, the distribution characteristics of the breaking wave current and suspended load transport in the surf zone are discussed in main. Based on the measured data of the waves, the form of breaking wave, the breaking wave current and the sediment concentration of suspended load in the offshore surf zone near Nouakchott, the Islamic Republic of Mauritania, the author has analized the law governing the distribution of longshore current and sediment concentration of suspended load by means of statistical method, and presented a calculation method for the longshore sediment transport in offshore surf zone.

Generation of electromotive force in igneous rocks subjected to non-uniform loading

When one end of an air-dry igneous rock block was uniaxially loaded in laboratory, there appeared an electromotive force that made electric currents flow from the stressed volume to the unstressed volume. Quartz-free rocks such as gabbro also generated this force, stronger than quartz-bearing rocks such as granite. This indicates that the piezoelectric effect of quartz and the electrokinetic effect of pore water do not make a large contribution toward generating the electromotive force. We focus on peroxy bond that is one of the abundant lattice defects in igneous rock-forming minerals. When mechanical loading deforms the lattice structure around this defect and breaks its bond, its energy levels change and act like an accepter. As an electron is trapped at this defect from a neighbor 02- site, a positive hole is activated there. They attempt to diffuse toward the unstressed volume through the valence band and are simultaneously affected by the attractive electric force with the electrons trapped in peroxy bonds. This leads to a polarization in the stressed volume and the generation of electromotive force between the stressed and unstressed volumes. Similar electromotive force may be generated in the Earth＇s crust where inhomogeneous stress/strain is changing.

Finding the buckling load of non-uniform columns using the iteration perturbation method

The aim of this study is to calculate the critical load of variable inertia columns. The example studied in this paper can be used as a paradigm for other non-uniform columns. The wavelength of equivalent vibratory system is used to calculate the critical load of the trigonometrically varied inertia column. In doing so, the equilibrium equation of the column is theoretically studied using the perturbation method. Accuracy of the calculated results is evaluated by comparing the solution with numerical results. Effect of improving the initial guess on the solution accuracy is investigated. Effects of varying parameters of the trigonometrically varied inertia and the uniformly tapered columns on their stability behavior are studied. Finally, using the so-called ＂perfectibility＂ parameter, two design goals, i.e., being lightweight and being strong, are studied for the discussed columns.

随机车流作用下拱桥吊杆疲劳性能研究

为研究吊杆的疲劳性能,以某拱桥为工程背景,在MATLAB中使用蒙特卡洛抽样建立考虑车型、车道、车距、车速、车重5种参数的随机车流模型,使用ANSYS求解吊杆在随机车流荷载作用下的应力时程,评估吊杆的疲劳损伤和寿命。结果表明,跨中长吊杆和拱脚附近的短吊杆疲劳损伤值高于其他吊杆;车流密度越大,吊杆疲劳损伤值越大,个别吊杆的不同车流密度下疲劳损伤值可相差20倍;车流密度对吊杆疲劳寿命影响很大,尽可能使用长时间的实测车流数据才能得到满意的预测结果。

基于电磁弹式索力传感器的悬索桥短吊索索力检测

采用传统索力测试方法进行短吊索索力测试的精度难以满足工程需求。本文以棋盘洲长江公路大桥悬索桥荷载试验为工程依托,提出基于磁弹原理及磁电效应的电磁弹式索力传感器检测吊索索力的方法,并与有限元分析结果以及频率法、应变法测试结果进行对比。结果表明,试验标定误差小于±2%,在荷载试验中,传统索力测试方法对吊索的测量误差偏大,采用电磁弹式索力传感器更为准确地测量了短吊索索力,解决了短吊索索力的测量难题。荷载试验的吊索索力测试结果表明,索力增量的测试值与分析值偏差小于±5%,实际索力的测试值与分析值偏差小于±4%。

悬浮物特征对砂加载混凝沉淀处理高悬浮矿井水实验的影响

高悬浮物矿井水高效快速处理是解决西部六省区煤炭资源化合理利用的关键。关于原水中悬浮物特征对石英砂加载混凝沉淀效果的影响则很少有系统的研究,影响机制也不清晰。为此,选用石英砂加载混凝处理陕西小保当煤矿典型高悬浮矿井水为研究对象,分析矿井水中悬浮物的粒径、煤岩比和初始负荷大小对石英砂加载混凝处理高悬浮物矿井水效率的影响。矿井水中悬浮物的粒径、煤岩比和初始负荷大小对石英砂加载混凝处理高悬浮物矿井水效率和沉降速度的影响明显。通常,混凝沉淀的去除效率和沉降速度随矿井水中悬浮物的粒径而显著升高,但当悬浮物的粒径过低(小于0.075 mm)后,沉降速率和去除效率明显降低。矿井水悬浮物的初始负荷过高(高于10 000 NTU)和过低(低于500 NTU)都会降低混凝去除效率和沉降速度。矿井水悬浮物中煤粉质量含量越高,砂加载混凝处理效率越低。该结果为有效提升砂加载混凝工艺的运行成效,缓解中国西部矿区水资源短缺的矛盾,同时对中国煤炭行业的绿色发展和矿区生态文明建设也具有重要的意义。

悬挂式单轨车辆车体结构静载荷工况的探讨

简述了悬挂式单轨交通的应用现状,介绍了悬挂式单轨车辆的组成及特点,对比分析了国内外城轨车辆相关标准中车体结构静载荷工况的不同要求。最后,结合悬挂式单轨车辆自身的技术特点和实际运营场景,提出了悬挂式单轨车辆车体静强度载荷工况方案。

海洋液压猫头内泄漏和负载效率试验研究

海洋液压猫头是钻机的基础配套部件,油缸内泄漏和负载效率是影响它安全高效运行的重要因素。为了研究以上两个参数,设计出带电子吊秤的试验装置。利用保压法测油缸中部230mm处的内泄漏,参照电子吊秤负载值来确认保压是否有效,再计算负载效率。通过以上方法对某海域8台液压猫头做试验研究,得到内泄漏试验值均低于标准值0.9MPa,内泄漏值合格;对负载效率值未达到0.88的4台液压猫头进行分部法分析,发现为活塞接头偏心和螺纹未拧紧所致。更换偏心的活塞接头并拧紧后,重复试验,均达到要求。液压猫头在2020年出厂后于海上正常生产运行。未来液压猫头须调整优化油缸密封:适当增加内泄漏标准以换取更大的负载效率;给动滑轮加导向装置,以稳定负载效率。研究结果表明利用该方法试验液压猫头内泄漏和负载效率,直观量化了性能指标及结果,可行有效,为同类型或相似类型的试验提供了参考。

Using Artificial Neural Network to Estimate Sediment Load in Ungauged Catchments of the Tonle Sap River Basin, Cambodia

Concern on alteration of sediment natural flow caused by developments of water resources system, has been addressed in many river basins around the world especially in developing and remote regions where sediment data are poorly gauged or ungauged. Since suspended sediment load (SSL) is predominant, the objectives of this research are to: 1) simulate monthly average SSL (SSLm) of four catchments using artificial neural network (ANN);2) assess the application of the calibrated ANN (Cal-ANN) models in three ungauged catchment representatives (UCR) before using them to predict SSLm of three actual ungauged catchments (AUC) in the Tonle Sap River Basin;and 3) estimate annual SSL (SSLA) of each AUC for the case of with and without dam-reservoirs. The model performance for total load (SSLT) prediction was also investigated because it is important for dam-reservoir management. For model simulation, ANN yielded very satisfactory results with determination coefficient (R2) ranging from 0.81 to 0.94 in calibration stage and 0.63 to 0.87 in validation stage. The Cal-ANN models also performed well in UCRs with R2 ranging from 0.59 to 0.64. From the result of this study, one can estimate SSLm and SSLT of ungauged catchments with an accuracy of 0.61 in term of R2 and 34.06% in term of absolute percentage bias, respectively. SSLA of the AUCs was found between 159,281 and 723,580 t/year. In combination with Brune’s method, the impact of dam-reservoirs could reduce SSLA between 47% and 68%. This result is key information for sustainable development of such infrastructures.

The Intra-Annual Variability of Discharge, Sediment Load and Chemical Flux from the Monitoring: The Yukon River, Alaska

The covered-ice breakup in subarctic to arctic rivers in the early snowmelt season often gives any damage to instruments monitoring physical and chemical factors of water. The serious condition has brought few time series data during the snowmelt runoff except the river stage or discharge. In this study, the contribution of snowmelt runoff to the discharge and sediment load is quantified by monitoring water turbidity and temperature at the lowest gauging station of U. S. Geological Survey in the Yukon River, Alaska, for more than 3 years (June 2006 to September 2009). The turbidity was recorded by a self-recording turbidimeter with a sensor of infrared-ray back-scattering type, of which the window is cleaned by a wiper just before a measurement. The turbidity time series, coupled with frequent river water sampling at mid-channel, produce time series of suspended sediment (SS) concentration, particulate organic carbon (POC) concentration and particulate organic nitrogen (PON) concentration (mg?L–1) by using the high correlation (R2 = 0.747 to 0.790;P 11 to 2.01 × 1011 m3), 8.7% - 22.5% of the annual sediment load (3.94 × 107 to 5.08 × 107 ton), 11.6% - 23.7% of the annual POC flux (4.05 × 105 to 4.77 × 105 ton), and 10.3% - 24.5% of the annual PON flux (2.80 × 104 to 3.44 × 104 ton). In the snowmelt season, the peak suspended sediment concentration preceded the peak discharge by a few days. This probably results from the fluvial sediment erosion in the river channels.

Incipient Motion of Bed Load Sediment and Its Application in the Three Gorges Hydro Project

A formula for the calculation of critical shear stress of non-uniform sediment was developed by on river bed has been established while considering the relative degree expose of grains.The values of the Coeffi- cients in the formula have been obtained.The formula has been verified with prototype observation data, flumes data of both nature and lightweight sand.The computed results fully reflect the characteristics of thresh- old motion of non-uniform sediment.The result have been used in some physical mo...

三峡建库后长江中游非均匀悬移质挟沙力变化

水流挟沙力变化是研究水库下游悬沙输移及河道演变的核心问题之一。以长江中游沙市—汉口沙质河段为研究对象,引入韩其为非均匀悬移质不平衡输沙中水量百分数、挟沙能力级配等概念,阐释了三峡建库前后非均匀悬移质挟沙力变化及其影响因素。建库后,沙市、监利站各流量级下床沙转为挟沙力的水量百分数均明显增加,螺山、汉口站分别超过临界流量30000 m^(3)/s和35000 m^(3)/s时,床沙转为挟沙力的水量百分数有所增加;沙市—城陵矶河段水流挟沙力减小程度大于城陵矶—汉口河段,其中沙市—城陵矶河段<0.125 mm粒径组挟沙力大幅减小,城陵矶—汉口河段<0.25 mm粒径组挟沙力减小。沙市—城陵矶河段水流挟沙力减小主要受挟沙力平均沉速ω^(*)变化影响,城陵矶—汉口河段水流挟沙力减小受挟沙力平均沉速ω^(*)和挟沙力判数U 3/h的共同影响,其中螺山、汉口站分别不超过临界流量30000 m^(3)/s和35000 m^(3)/s时,挟沙力判数U 3/h的贡献率较大。

Analysis of energy pile groups subjected to non-uniform thermal loadings

Sequentially coupled thermal-stress finite element analyses were performed to investigate the mechanical behaviors of an energy pile group subjected to non-uniform thermal loadings.The group effect was highlighted by comparing the thermo-mechanical responses with those of the single pile case.Due to the thermal interactions between piles,the group piles’temperatures were higher than that of the isolated single pile.If only part of the piles served as heat exchangers,i.e.,the pile group was thermal loaded unevenly,there were dif-ferential deformations between the heated and the non-heated piles.Due to the pile-raft-pile interaction,the axial forces of the piles chan-ged significantly.The location of the heated pile had an important influence on the thermally induced axial force,while the effect of the soil’s coefficient of thermal expansion was not significant.Inspired by the numerical result,a simplified method was proposed to capture the main characteristics of energy pile groups and to facilitate the design.The proposed method was developed in the framework of the traditional load transfer approach,and the pile-raft-pile interaction was included.By applying different temperature increments to dif-ferent piles,the non-uniform thermal loading was modeled.The proposed method was verified by comparing with the finite element anal-ysis results and the data collected from the literature.

输电线路异物清除空中机器人飞行控制技术研究

针对人工清理输电线路上的异物效率低且存在较大风险的问题,本文提出了一种用于输电线路清理的空中机器人,该空中机器人通过悬挂作业工具实现线路异物清理。本文针对输电线路异物清理空中机器人建立了其携带负载时的运动学和动力学模型;针对空中机器人携带负载后带来的重心变化、接触作业时的接触力与参数摄动等问题,研究了线性自抗扰控制方法。对空中机器人进行了仿真实验,验证了本文提出的空中机器人的可行性和线性自抗扰控制方法在空中机器人上具有较好的控制效果和抗干扰能力。

金沙江下游区间来沙驱动因子分析及产沙预测模型

随着长江上游梯级开发的快速推进,金沙江下游干支流来沙占比失衡现象日益突出,区间水沙实测资料欠缺的问题严重影响了对干流库群泥沙淤积的预测。为系统性了解并掌握金沙江下游区间内泥沙分布全貌,明晰区间来沙时空异性特征以及归因,基于已有支流水文站泥沙序列与因子集,采用秩相关分析研究了区域内地形、气候、土地覆被、空间尺度各类因子对流域产沙的潜在影响和各因子之间的变化独立性。通过参数降维与双重回归分析相结合的方法识别关键因子组合并构建输沙模数预测模型。研究结果表明:8°以上坡度占比、气温和集水面积的驱动因子组合能够较为完整地解释研究区域产沙机制,并在此基础上建立了能解释约92%输沙模数变化性的预测模型。根据模型计算得到广大无实测资料区域的输沙模数分布范围为87~1189 t/(km^(2)·a),近50 a来减小幅度约50~300 t/(km^(2)·a)。在此基础上识别白鹤滩、溪洛渡高产沙及上下游低产沙区间,并分析了该空间不均衡特征的削弱趋势。