• 全国中文核心期刊
  • 中国科技核心期刊
  • 美国工程索引(EI)收录期刊

2008 Vol. 19, No. 1

Display Method:
Sediment deposition analysis of downstream access channel of permanent ship lock during 135m operational phase of Three Gorges reservoir
HU Xing-e, LI Yun-zhong, LI Ming-chao
2008, 19(1): 1-7.
Abstract:
Based on the abundant data of the sediment deposition and water-sediment factor change in the downstream access channel and entrance area of the permanent ship lock during 135m operational phase,a series of parameters and relationships are analyzed.These parameters include the deposition quantity and its distribution,the deposition configuration of entrance bar,the deposition mechanism and the rermval time of sediment.Then,some relational equations are established,such as sediment concentration between the entrance and the Yangtze River,inclined flow velocity of the entrance and discharge of the Yangtze River,the aggradation and the incoming sediment of entrance bar.And,the deposition of the density and circulation flow in the downstream access channel and entrance area are verified by the inverted density flow theory.The results indicate that the depositions in the downstream access channel and entrance area develop mainly in the major flood period (Jul.-Sept.),and one desalting in the later flood stage (Oct.-Dec.)can satisfy the shipping depth demand.
Monitoring and analysis of variation in the Yellow River estuary based on remote sensing under the change of environment of flow and sediment
XU Mei, LI Ji-ren, HUANG Shi-feng, LI Xiao-tao, MENG Fan-guang
2008, 19(1): 8-12.
Abstract:
Waterhead is a dominant factor for controlling the development of the Yellow River's new wetland.The change of flow-sediment condition results in the variation of coastline, land area, land cover and environment of the Yellow River estuary.In this paper, the feature of flow-sediment and the corresponding variation in the Yellow River estuary are monitored and analyzed based on the remote sensing for the nearly several years before and after 2000.The result shows that the Yellow River estuary extends toward the sea direction and land area increases in the new flow-sediment environment but not evidently In general, the environment quality in the estuary is improved.And the flow-sediment condition of 2003 is perfect.
Experimental study of feature of the cohesive sediment lamination movement
WANG Jia-sheng, CHEN Li, LIU Lin, HUANG Rong-min
2008, 19(1): 13-18.
Abstract:
In this article the experiments of open channel flume is done to study the coherent sediment motion in weak dynamic condition, the experimental results indicate that the special movement form "the lamination movement" emerges when the condition (flow and sediment density) is contented.When "the the lamination movement" occurrs, the sediment density along perpendicular profile presents "the steps and ladders".The peak value of the fluent speed emerges in the middle of the perpendicular of the flow, then reduces to the water surface and the bottom of the flume.The cohesive sediment flocculation and construction of flocculation net are the basic reason for the emergence of the lamination movement forms.The fluent condition is the most important factor for the lamination movement formation, and the lamination movement forms in the certain fluent intensity scope.The sediment density has the tremendous effect on the lamination movement formation.Different sediment densities form the different lamination movements and the hydrodynamic conditions, that is the silt density increases, the intensity of the fluent forming the lamination movement also increase correspondingly.
Numerical simulation study on longitudinal profile of scouring funnel
FENG Xiao-xiang, ZHANG Xiao-feng, WEI Zhi-lin, LI Jian-bing
2008, 19(1): 19-26.
Abstract:
An optimized method is put forward for the conventional sigma coordinate system which will cause a dynamical change size of an orifice and have difficulty in the specifying the free surface boundary condition.And 1D flow model is adopt ed to determine the vertical 2D free surface boundary, namely, "movable rigid-lid" used to get the boundary condition.Based on the flow characteristic in front of the bottom orifice and stability analysis of the underwater slope, it introduces the boundary condition of sediment exchange near the riverbed and the expression for the critical condition of riverbed sliding in the initial stages of the bottom orifice outflow respectively.So a vertical 2D flow and sediment mathematical model for bottom orifice outflow is proposed.It is validated by the flume experimental data for the riverbed deformation of scouring funnel shape with rigid apron.Satisfactory agreement is obtained in the length of scouring even segment and the slope of scouring funnel.It shows the rationality and reliability of this proposed model.
Experimental study on the incipient plunging point of stratified flow of turbidity currents and debris flows
YU Bin
2008, 19(1): 27-35.
Abstract:
World-wide attention has been paid to the plunging point because it is the forming and persisting conditions of strat ified flows.Incipient plunging point Froude number (Fr) is the forming condition of stratified flows and the stable plunging point Fr is the persisting condition of stratified flows.A series of experiments were conducted in a flume to study plunging point of stratified flows of low density turbidity currents, high density turbidity currents and debris flows The rule of incipient plunging point Fr in uniform and straight channel was found.The incipient plunging point Fr of stratified flow is direct proportional to the head velocity of stratified flow at given width of channel and given concentration of sediment.Compared the different experimental results from others references, the results of this study have good reliability as they have good consistency.The results of this study are applicable only for the incipient plunging point instead of the stable plunging point and the transition between the incipient plunging point and the stable plunging point.But the stable plunging point Fr of stratified flows of high density turbidity currents and debris flows is very close to their incipient plunging point Fr.This approach is more desirable when the debris flow has strong viscosity.
Modelling hydrological cycle system in Zhalong wetland based on reservoir model concept
XU Shi-guo, LIU Da-qing, TANG Xiao-liang
2008, 19(1): 36-42.
Abstract:
This paper presents a hydrological cycle system model based on reservoir model concept to model hydrological cycle processes in Zhalong wetland.It is divided into 9 reservoirs based on the topography and the project construction Each reservoir is modelled based on water balance function.The model works using the input data from 1971 to 2003.The parameters of the model are calibrated by the 11 years (1971-1981) outflow runoff data.The validity of the model is verified by the 6 years (1982-1987) outflow runoff data and 12 flooded areas obtained from Landsat TM images.The efficiency coefficient of outflow runoff is nearly 0.90 and the relative error less than 3.0%.The modeled flooded areas are also satisfying.The results show that the proposed model has a good performance in modelling wetland hydrological cycle system.
Studies of the energy balance and evapotranspiration over the typical marsh wetland in Sanjiang plain
SUN Li, SONG Chang-chun
2008, 19(1): 43-48.
Abstract:
During the period from May to October 2006,the continuous eddy covariance measurements is used to investigate the seasonal variation of energy balance and evapotranspiration and to determine the total evapotranspiration over the typical marsh wetland in Sanjiang plain.According to the regression analysis,the total evaporation and transpiration are estimated.The results show that there is obvious seasonal variation of the energy balance of marsh wetland.Overall,the latent heat flux dissipated 45.5% of the net radiant energy,sensible heat flux 27.9% and the storage heat flux 26.7%.The total evapotranspiration from May to October is 310.6 mm,and the highest month-average daily evapotranspiration appears in July.The total evaporation which accounts for about 71% of total evapotranspiration is about 221 mm,and the total transpiration accounts for 29%.Therefore,the evaporation is the main contributor to the evapotranspiration over marsh.
Hydrological cycle and improvement alternatives for urban area
LIAW Chao-hsien, CHAN Li-mei, CHEN Chia-liang, CHIU Yie-ru
2008, 19(1): 49-53.
Abstract:
Urbanization comes along with population increment and centralization,which enlarges the density of impervious areas,results in dwindling ground water replenishment and deteriorating urban water cycle etc.In order to have a better understanding and quantify the impacts from reducing impervious areas and installing rainwater catchment systems on long-term urban water cycle,building up an appropriate urban water cycle model is needed.The watershed of the Liu-guan pumping system in Taipei city has been chosen as the study area.Parameters in the rmdel are calibrated and verified using measured data from the inflow of the pumping station.Sensitivity analysis of these parameters is also conducted.The hydrologic changes among surface runoff,infiltration and evapomanspiration for changing percentage of impervious areas by installing permeable pavement are examined.Also different percentages of existing buildings are assumed to install roof rainwater catchment systems and their impacts on surface runoff and water supply are evaluated.The urban water cycle model established in the study may easily assess the changes of water cycle by changing land uses and provide as a useful tool for urban planners.
Seasonal flood frequency analysis and flood prevention standard
XIAO Yi, GUO Sheng-lian, LIU Pan, XIONG Li-hua, FANG Bin
2008, 19(1): 54-60.
Abstract:
The flood quantile estimated by conventional seasonal floodfrequency is less than or equal to annual maximum estimator,and can not satisfy a given flood prevention standard.A bivariate joint distribution with Pearson Type Ⅲ distribution margins is developed based on Gumbel-Hougaard Copula and used to describe two seasonal maximum flood series.A relational equation between annual maximum flood and seasonal maximum floods is developed,and the relationship between the frequencies of seasonal flood quantiles and design flood prevention standard is also given.Ultimately a new seasonal flood frequency analysis method is proposed and developed.Compared with the conventional annual maximum method,the seasonal design floods estimated with the proposed method are slightly greater in the main flood season and less in other flood seasons.It is shown that the proposed method could satisfy flood prevention standard and provide a new way for determining seasonal design floods.
Spatial heterogeneity of soil moisture in alpine meadow area of the Qinghai-Xizang Plateau
LI Yuan-shou, WANG Gen-xu, DING Yong-jian, WANG Yibo, ZHAO Lin, ZHANG Chun-min
2008, 19(1): 61-67.
Abstract:
In this paper geo-statistical theory and methods are used to study the spatial heterogeneity of loll moisture characteristics in shallow profile (0~40 cm) of alpine meadow areas(110 m×90 m) in the Qinghai-Xizang Plateau.The 352 sampling points are fixed in total Using the grid sampling method(10 m×10 m space).The results show that in alpine meadows 0-30 cm depth of coverage area,there is a high degree of spatial heterogeneity of soil moisture.Within 87.3%-74.9% spatial heterogeneity,part of the spatial autocorrelation is at 0-30 cm depth.The auto-correlation factors at 10-201 m scale play an important role in the 0-30 cm soil moisture spatial heterogeneity.But spatial heterogeneity of mil moisture at the layer of 30-40 cm depth can be controlled by the random and auto-correlation factors.With the increase of depth the fractal dimension D has a gradually increasing trend.The warthy noting is that the random factor will increase at soil depth for soil moisture spatial heterogeneity.From the C0/(C+C0) comparable values of soil four layers,the minimum value is in the lowest level of thi s 10-20 cm,the level of system variables is shown in the highest degree of spatial autocorrelation.mil moisture content of the layer 0-30 cm of alpine meadows area is affected by precipitation,vegetation growth,mot distribution,soil characteristics and impacts of human interference et al.
Constant water levels at the upstream of sluice gates in a large-scale transferring channel
FANG Shen-guang, LI Yu-rong, WU Bao-sheng
2008, 19(1): 68-71.
Abstract:
Aimed to study on whether constant water levels immediate at the upstream of control gates can be maintained in the Middle Route of South-to-North Water Transfer Project, the different unsteady flow transit ional processes are simulated when inflow at the head, openings of control gates and the flow rates divided by outlets are changed simultaneously.The results show that a very long time is needed to reach a new steady state of the flow in the channel under operations of all control gate openings simultaneously and the transitional time needed for the decreasing of gate openings is much longer than that for their increasing.Water levels at the upstream of control gates vibrate to a big extent in transitional processes and can restore to their initial values finally.More studies are needed to find out the methods of gate operation that can fully realize constant water surface elevations immediate at the upstream of sluice gates for real time channel regulations.
Threshold value of epikarst runoff in forest karst mountain area
JIANG Guang-hui, WU Ji-chun, GUO Fang, LI Hua-ju, SUN Hai-long
2008, 19(1): 72-77.
Abstract:
An epikarst spring in the forest karst rmuntain area in the southwestern China is selected for this study.The continuous auto-monitoring of the spring's di scharge,pH,electrical conductivity (EC),water temperature(T) and rainfall has been done for more than one year.The results indicate that,generally,in rainy sewn,the spring's pH shows a temporary decrease after rainfall,and the spring's EC increases temporally,while the spring's T displays a transitory increase.However in dry season the behaviors of these parameters are different.According to the spring's different reflection to rainfall ranging from faintness to intensity,the response can be classified into three grades.The first grade is characterized by unchange after rain in discharge,pH, EC and T.The second grade shows slow and little change in a part of these parameters.The third grade indicates a distinct change in all of the four parameters.Basing on the spring's response,it is determined that the threshold value of runoff in the epikarst is 12 mm of rainfall.For epikarst,the threshold value is the mark to distinguish between the effective and invalid rainfall.It is also an important parameter for the study on the formation of gn}undwater resources.
Numerical modeling of multi-directional random wave transformation in wave-current coexisting water areas
ZHENG Jin-hai, Hajime Mase
2008, 19(1): 78-83.
Abstract:
Based upon the wave action balance equation,a numerical predicting model is developedfor multi-directional random wave transformation in the wave-current coexistingfield,in which the diffraction effect and the Doppler shift of dispersion relation are taken into account.A bore based formulation is used to parameterize the energy dissipation associated with coupled current and depth limited wave breaking.The governing equation is discretized by a forward marching first order upwind finite difference method.The wave height distribution of uni-and multi-directional incident random waves are calculated with and without considering the nearshore currents effect.Results show that the predictions considering the current effect produce a preferable fit to the experimental data and perform well in simulating the wave height accretion due to rip currents.The mutual model-data comparisons reveal that the present model is applicable for the random waves propagating in wave-current coexisting water areas.
Model experiment study of effect of discharge atomization for energy dissipation by hydraulic jump
WU Shi-qiang, WU Xiu-feng, ZHOU Hui, CHEN Hui-ling
2008, 19(1): 84-88.
Abstract:
The phenomenon of discharge atomization occurs as hydraulic structures discharging,affecting the safety of power stations,electrical equipment and producing environmental pollution.In this study,the means of large scale model is used to study the discharge atomization problem for Xiangjiaba power station.The feedback analysis is carried out for the model law of atomization using the field measured data of Wantang power station similar to that of Xiangjiaba power station on the side of energy dissipation.Atomization intensities and canes of Xiangjiaba power station is forecasted.
Numerical simulation of plug energy dissipater flow
YIN Ze-gao, SHI Bing, ZHAO Lin, SUN Dong-po
2008, 19(1): 89-93.
Abstract:
In the case of the plug energy dissipater flow, the characteristic of turbulence is studied firstly, then 3-D RNG k-ε mathematical model and the calculation program are established and verified properly by the physical model test data Based on the computational results of mathematical model, the head loss of plug energy dissipater flow is analyzed and generalized, showing that the head loss coefficient reducs rapidly, then increases evidently and finally increases according to linearity relation, when the ratio of plug section length to plug section radius increases from small value.According to the same radius of pressure tunnel, the head loss coefficient is affected by a variety of plug section radius more than that of plug section length, which can give reference to the design of plug energy dissipater.
Mixed-water model of watershed based on incomplete mixing pattern
WANG Chuan-hai, ZHU Yan, CHENG Wen-hui, XIANG Xiao-hua
2008, 19(1): 94-98.
Abstract:
In order to reduce the numerical diffusion error of the convey-diffuse equation, the concept of concentration on cross section is introduced to calculate the mean concentration of river sections, and a new finite control volume method is put forward based on the incomplete mixing pattern.Depending on above concept, a income water component model is set up, which simulates the water source composition of the basin and describes the spatio-temporal changes of different water sources.By applying the present method in calculation, the results are in agreement with the measured data, indicating that the present method of incomplete mixing pattern can improve the accuracy of income water calculation.
Assessment of eutrophication in the Yangtze River estuary and its adjacent waters
SU Chang, SHEN Zhi-liang, YAO Yun, CAO Hai-rong
2008, 19(1): 99-105.
Abstract:
According to the investigations of four mid-months (Feb.,May,Aug.,and Nov.)of seasons in 2004,we choose COD,DO,PO4-P,DIN,Chl-a as assessing indexes,and use the artificial neural network to assess eutrophication in the Yangtze River estuary and its adjacent waters.The results show that the waters of eutrophication mainly concentrate round the rivermo uth,and the extent of eutrophication gradually decreases from the rivermouth to the east and northeast.The areas of eutrophication are almost distributed in the side of salinity bellowed 20 and have seasonal variations along with the changes of Yangtze River diluted water.The phenomenon of eutrophication is more serious in May and August than in other months,and both have the trend of turning around to the northeast,which may be caused by the diluted water turnaround with the flood coming in May.The transection distributions of eutrophication in each rmnth indicate that the grades of eutrophication change from high to low level,from rivermouth to the east,and it has complex variations in the vertical direction.The analysis shows that DIN is the main control factor for the assessment results of eutrophication.
Distribution of pCO2 in Hongfeng lake in summer stratification
LÜ Ying-chun, LIU Cong-qiang, WANG Shi-lu, XU Gang
2008, 19(1): 106-110.
Abstract:
Water column samples taken from the northern and the southern lake centers in Hongfeng lake in summer stratification were measured about their water temperature,pH,the concentration of HCO3-,DO,Chla,NH4+,NO3-,and PO43-.The pressure of CO2 (pCO2) was calculated by the chemical balance and the Henry's law.The results show that the photosynthesis,the degradation of the organic matter and the thermal stratification are the main factors regulating the distribution of pCO2 in Hongfeng lake.The unsaturation of CO2 in the epilimnion is caused by the fixation of CO2 during the photosynthesis and the sharp increase of CO2 in the metalimnion may be due to the degradation of the photosynthesis production.In addition,the pCO2 in the hypolimnion near the sediment is the highest and has an increasing tendency,which indicates that the degradation of organic matter in the sediments has an important effect on the pCO2 in the hypolimnion.The thermal stratification results in the significant variation of pCO2 in the water column and the accumulation of CO2 in the hypolimnion.Finally,the variation of pCO2 is concomitant with the variation of the nutriments:the consumption of nutriments during the photosynthesis took place in the upper water column and the release of nutriments during the degradation of the organic matter in the lower water column.
Hydrostatic settling suspended matter of large shallow lake
XIANG Jun, PANG Yong, LI Yi-ping, WEI Hai, WANG Peng, LIU Xing-ping
2008, 19(1): 111-115.
Abstract:
In order to study the hydrostatic settling of suspended matter of large shallow lake,Four experiments,based on the Taihu lake,were conducted in the laboratory for hydrostatic settling behavior of suspended matter in Taihu lake in April and May,2005.The settling velocity of suspended matter was calculated by McLaughlin method.The results show that the settling velocity of particular inorganic matter(PIM) is the biggest,and the second biggest one is that of suspended matter (SS),the smallest one is that of particular organic matter(POM).During the same time of settling,the settling velocity of PIM is 1.6-2.0 times bigger than that of SS,the settling velocity of POM is 0.3-0.7 times bigger than that of SS,and the settling velocity of PIM is 2.5-5.5 times bigger than that of POM.The results also show that the suspended matter concentration decays exponentially with time,which is more obvious when the percentage of inorganic suspended matter accounting for total suspended matter is higher.When the suspended matter concentration is low,no clear relationship is found between settling velocity and suspended matter concentration.But settling velocity obviously rise with the increase of suspended matter concentration while the latter is high.
Prediction model of chaotic time series based on support vector machine and its application to runoff
YU Guo-rong, XIA Zi-qiang
2008, 19(1): 116-122.
Abstract:
Chaos theory and support vector machine have great capability of dealing with nonlinear matter.Based on the phase-space reconstitution theory,the prediction rmdel of chaos time series is built by using the support vector machine in this paper,the method,the characteristic,and the selecting of the key parameters in the modeling is discussed.Fnrstly the phasespace re-constitution is made by saturated correlation dimension,so that information of monthly runoff series is profoundly investigated.At the same time,the maximum Lyapunov exponent is computed using the improved small-data method,and it is used to recognize the chaotic feature of the monthly runoff at YiChang.In the application of chaos time series using support vector machine model to predict the rmnthly runoff,the RBF kernel function is introduced,which simplified the course of solving non-linear problems.It is shown by the study case that the rmdel proposed in the paper can process a complex hydrological data sieres better,and has better generalization and prediction accuracy.
High precision numerical integral on free surface boundary of 3-D unsteady seepage problem
ZHENG Gui-lan, WANG Yuan, PEI Li-hua
2008, 19(1): 123-128.
Abstract:
In Getechnical engineering, such as slope, underground tunnel, dam and dike, and soil foundation etc, 3-D unsteady seepage problem often occurs.In performing the numerical analysis of unsteady seepage problem, it is necessary to calculate the integral on free surface boundary.In the paper, a high precision numerical integral method is presented.Based on the 8-node isoparametric element, the equat ion of the free surface boundary in an element is obtained firstly according to zero water pressure condition, and then the integral on the free surface boundary is translated into the integral on the plane ξη of local reference.And the integral region is calculated according to the projections of the intersecting points where free surface and the boundaries of the element cross.Finally the whole integral region is divided into several triangle sub regions, and the Simpson method with changing steps is performed to calculate the integral on each triangle sub-region.The high precision numerical integral method can avoid the assumption that the free surface is a plane within an element.It can improve the calculation accuracy, especially for the case that the free surface within an element varies very sharply The applications in both the sand tank model and an example of homogeneous earth dam are given, it shows that the method is practical.
Recent development and universality evaluation of ET0 calculation formulas
SU Chun-hong, CHEN Ya-xin, XU Bing
2008, 19(1): 129-136.
Abstract:
This article, through summarizing the progresses in the evapotranspiration (ET0) methods research, analyzes representative ET0 computation methods emphasized on three periods of the world: modificative Penman (MP), Penman-Monteith (PM) and standard ASCE-PM.We take 20th century 90's last stages and 21th century initial period's world newest 19 experimental achievements with lysimeter's actual value rating ET0 value as the foundations, analyzing general usage of the ET0 computational method regarding the different climatic conditions Although the effect of PM method application is desirable in many areas, many local effects are still unsatisfactory; the method MP and so on are more suitable in part of areas; the PM and MP method are not popular, the special attention must be paid to the standard ASCE PM method.In brief, these kinds of half theory (semi-empirical) methods only suit in certain areas By comparison of MP and PM method, we can't simply evalu ate which kind of method is superior or which kind of method calculates the ET0 value big (or value is small), and we should consider different geography, the climatic conditions and lysimeter experimental result.In the article, there is also corresponding suggestion for the research in the future, which is helpful to the thorough research of ET0 method discipline.
Development in numerical and experimental study of the multiple jets
LU Qi-ling, CHEN Gang
2008, 19(1): 137-146.
Abstract:
The multiple jets is an important type of fluid flow with its application in various engineering fields and a highly complex turbulent flow due to the action of entrainment and mixing of the high speed flow.These phenomena were observed in number of previous investigations in theoretical,experimental and numerical studies,and some structural features and flowing mechanisms are revealed.In this paper,from the aspects of the numerical simulation and the experimental study,the present study methods and results are analyzed,and the forecasting ability of both the different turbulence models and various measuring ways are summarized.In the end,some unsettled issues are discussed and the developing directions in this field are also pointed out.