Abstract: In order to improve the computational stability and accuracy,the Preissmann's four point implicit difference scheme is used in a 1-D model,and the improved Double Sweep Implicit method is presented in a 2-D model by using the Eulerian Lagrangian method instead of upwind finite difference.An junction control method for water level is established in the 1-D model.The 1-D model is joined together with a 2-D model at the river mouth,which avoids the requirement of the grid over lapping at river segment.The downstream boundary of the 1-D model is the up boundary of the 2-D model.Using the interface section method for transferring hydraulic factors,a new coupled numerical model is established.Application of the coupled model to the Pearl River Delta is carried out for the calculation of the water level,discharge and velocities.Results of the tem poral and spatial distribution of the water level,discharge and velocities coincide with the measure data quite well.
Abstract: A 2-D numerical model is developed to simulate flow and suspended sediment concentration in oscilating turbulent boundary layer over plane bed,which is based on the N-S equations with the Smagrionsky's subgrid-scale turbulence model The calculation results agrees well with the flow characteristic and sediment concentration measured in experiment practically.
Abstract: The shortage of the current standards for estimating the incipient ration of sediment particles is analyzed in this paper. The standards for estimating incipient ration of sediment not only should consider the condition of river flow,but also consider the relative location of sediment grains within riverbed. The condition of incipient rmtion for one diameter grain is not a constant,but a variant located in a region and varying with the relative expose degree of the grain. The formula for calculating the conditions of threshold rmtion is obtained according rolling ride based on force and momentum balances,and the value of dimensionless critical shear stress of each status is calculated theoretically.
Abstract: Based on the measurements during 1950-1960 and 1974-1985,the analysis are made on the influence of the floods from different sediment source areas on the relationship between the discharge and the sediment concentration at stations of Huayuankou,Caocun,Aishan and Lijin on the lower Yellow River. When the runoff between Hekou and Longmen,Malian River and Beiluo River accounts for rmre than 20% or 25% of the total water wlumes at stations of Sanmenxia,Heishiguan and Xiaodng,the flood is referred to as from the coarse sediment source area of the Yellow River. When the runoff between Hekou and Longmen,Malian River and Beiluo River covers less 20% or 25% of the total runoff at stations of Sanmenxia, Heishiguan and Xiaodong,the flood is referred to as from the fine-sediment source area or from the area with small sediment concentrations. As a result,the relationship between the mean discharge and the mean sediment concentration at stations of Huayuankou,Caocun,Aishan and Lijin on the lower Yellow River is divided into two classes:(1) the mean sediment concen-tration increases greatly for small variation in the mean discharge,and (2) the concentration does not increase much even when the mean discharge increases by several times. Meanwhile,the flood between Hekou and Longmen,Malian River and Beiluo River causes great increase in the mean inflow sediment coefficient and the mean sediment concentration of the lower Yellow River and consequently leads to a large amount of the deposition.
Abstract: Based on oceanic temperature data of 1955-2001 in the tropical Pacific,the changes of the west Pacific warm pool oceanic temperature anomalous signal pathway are analyzed and discussed in the paper.The pathway that influences anomalous signal of sub surface oceanic temperature in the west Pacific warm pool region is revealed.The analysis indicates that there is close relation between change of sub surface posit ive and negative oceanic temperature anomalous signal in the west Pacific warm pool region and the anomalous signal westward propagation in the north equatorial current.The signal in the north equator current propagated from the equator middle east Pacific toward the west Pacific warm pool region along the ther mocline,the cool and warm signal in the west Pacific propagated toward the equator middle east Pacific along the thermocline, and they have formed cyclone circulat ion pathway of tropical oceanic anomalous signal on thermocline curved surface.The westward propagation of the sub surface oceanic temperature anomalous signal in the north equatorial current is the important mechanism to lead to the warm pool region and the west Pacific and is a key factor influencing the El N ino and La Nina events.
Abstract: The radial basis function-artificial neural network(RBF-ANN)is a more excellent neural network,and is applied to flood level forecasting for tidal channel in this paper The parameters of the RBF-ANN are calculated by using the K-mean algorithms and the least square estimation algorithms Compared with the traditional BP algorithm,the RBF-ANN model is fast in convergence,and more valuable in practice Based on character of the tidal channel,the RBF-ANN model with some fore cast lead periods is presented The model is applied to flood level forecasting of Yihe River,and the result shows that the model work is very rapid and the satisfactory results are acquired.
Abstract: A new strategy involved in training sample and algorithm for networks weights is put forward in this paper in order to fully seek information of original data and expedite convergence rate.A forgetting factor and an expecting factor varying with time are designed into training.On the other hand,an exponential energy function is introduced for forming a new algorithm to modify the weights of ANNs.Two case studies are presented.The results show that the suggested strategy is reasonable and functional.
Abstract: By using the hetero-associative memory of nerve-network and the similarity of the error that can enlarge the real-time information,a comprehensive real-time correction method is presented.An auto-regressive(AR)model and a comprehensive correction method are both made for real-time correction of 11 floods in Qilijie Basin.The results show that a comprehensive correction method is more accurate and the forecast lead period is not lost,comparing with the AR model.The results of using the comprehensive correction method for testing the nearly 50 floods in six tributary basins of Minjiang Basin are satisfactory.
Abstract: The optimal water allocation under limited water supply is studied with a multi-source and multi-crop irrigation area as a background.Both optimal reservoir operation and optimal allocation of water to lands are considered in this paper.The whole irrigation area is divided into units according to the distribution status of water resources and land resources.On every unit is planted several crops.If the field where each crop in each unit is planted is looked upon as a soil reservoir,the optimization methods employed in the operation of multi-reservoir system can be used to study the optimal water allocation in irrigation area.The optimal control algorithm is employed in this paper.To show the validity of the integrated model,the three different models are simulated in this paper.In model Ⅰ,neither reservoir nor canal irrigation systems is operated optimally.In model Ⅱ,only optimal operation of reservir is considered.In model Ⅲ,only optimal operation of canal irrigation systems is considered.The case study shows that the integrated model can generate more benefit than the other three models,especially in drought years,and the optimal control algorithm performs well.
Abstract: Based on the shortage of water resources in the north of China,under the condition of definite crops planting scale, the limited water resources were allocated to different crops in deficit irrigation ways,which aims to get maximum benefit.By means of simulative technique and the method of controlling the lowest water content rate of soil in different growth period, considering the randomicity of rainfall,the irrigation decision-making software was developed for the optimal water allocation and real-time self-adjustment in irrigation practice.
Abstract: This paper presents a two-dimensional unsteady flow model(RBFVM22D),which is based on the finite volume method combined with unstructured triangle and quadrilateral grids in the Yangtze River in Jiangsu province.The simultaneous hydrodynamic,water quality and remote sensing data are used to calibrate and verify the model.The results agreed well with the field data.Based on the investigation of the water quality,pollution sources and stability of the river bank,the main pollutant mixed belts in generalized pollutint and the relationship between the area of the belts and the discharged pollutants are computed.The water quality situation in the water supply place is analyzed and the suitable pollution control measure is given.
Abstract: The Taihu Basin waste load model is built by studying the discharging direction,producing amount and treatment coefficient of pollution load for various point sources and non-point sources in the Taihu Basin.The integrated input data of various waste loads of pollutant sources are acquired by calculating output of the Taihu Basin waste load model,which is input data for the Taihu Basin water quality model.The output and treatment amount of pollutants of various pollutant sources in the Taihu Basin can be visually displayed by the figure,quantifying the waste load difficult for a direct measurement in the whole Taihu Basin.
Abstract: Based on analysing runoff yield and flow concentration characteristics in urban drainage systems,a mathematical model for storm water logging simulation is established by using the hydrologic and hydraulic methods.The model can be used to simulate quantity,depth,cover area and lasting time of storm water logging during a storm event,and demonstrate dynamically the logging processes incorporated with GIS,providing necessary information for decision of flood prevention and disaster reduction.
Abstract: As an example,the impact of the levee realignment project on the flood control of Wenzhou city is studied by a 2-D tidal flow mathematical model.The verifications of the model show that the tidal levels computed by the model are in good agreement with the field data,and the tidal velocity and rate of discharge are also in accordance with the data recorded.The variance in computation versus actual results is less than 10%.Therefore,the model can be used to accurately predict the changes of tidal level,flow velocity and discharge to forecast the effects of the project.As the majority of the riverbank moved outward is in the concave area of the river,the project will create a smoother outward arc for the riverbank.It is shown from computed results that the maximum high tidal level increases 0.03-0.04 m and 0.04-0.08 m for project scheme 1 and scheme 2,respectively,in the flood frequency of 1%in the reach from the Yutoushan to the Mei'ao.With an annual mean discharge of 450 m3/s,the vertical average velocity in the reach from the Tashan section to Yuqishan section increases 6% to 22% after the completion of project scheme 2.The change in velocity in the reach outside of the project is small.The impact of the project on the bifurcation ratio of the Jiangxinsi branch is very small.The river blocked by project scheme 1 is much smaller than that by project scheme 2,and the change in velocity created by project scheme 1 is also smaller than that by project scheme 2.The results computed by the model can be used as a reference for decision making.
Abstract: Flood-plain wetland is one of the important types of wetlands with special ecoenvironmental functions,and also a significant component of terraqueous landscapes and ecotones of watershed ecosystems.In this paper,ecoenvironmental functions of flood-plain wetland are discussed,and scientific and reasonable integration management implications are put forward according to the main floodplain wetland ecoenvironmental problems in China.
Abstract: According to the hydrogeological conditions,underground water resource distribution and present exploitation and development situation of the receiving water areas in Henan province,fifteen advantageous places of underground reservoir regulating storage with three kinds and five types are divided.This paper preliminarily calculates the design reservoir capacity, the optimum adjusting and controlling water capacity,and presents how to adjust,control and manage the regulating water sources.
Abstract: The 218P0 sounding method is a new way of searching for water. This article mainly studies the operation progress of the method,and how to identify aquifers,determine the number of aquifers,analyze water rich nature and calculate the depth of the base plate of aquifers in accordance with the practically measured diagrams. The related theory is tentatively probed.
Abstract: In the research and applications of bend circulation theories,the Rozovskii's formulas are very important,but the universality of these formulas is weak,because there are two different formulas for smooth and rough bed surface respectively Besides,it is unreasonable to take 0.5 as the Karman's constant in these formulas In consideration of the above problems in the derivation of the Rozovskii's formulas,the general formula of circulation velocity profile and the general formula of the cross surface slope are derived by use of the non-sliding condition at the bottom in this paper Comparison of verification of the experimental data with smooth and rough bed surface respectively with the Rozovskii's formulas shows that this general formula fits in best with reality and holds true for bed surfaces of different roughnesses.Thus it is a general formula for computating the circulation velocity profile at river bends.
Abstract: A numerical solut ion for a backward facing step flow(BSF)by the action of lower-wall slipping is simulated with the hybrid finite analysis method.Based on the comparison of the computed results between lower wal slipping BSF and typi cal BSF,the flow configuration effected by lower-wall slipping is analyzed.The comparison displays that the lower-wall slipping BSF has more complicated vortex structure with three vortexes in its flow region.Two small vortexes locate the lower with their lengths decreasing mainly with the increase of lower-wall slipping speed;one large exists in the upper and it lengthens with the increase of both lower wal slipping speed and the Reynolds number,but is more significantly af ected by the Reynolds number.
Abstract: An automatic weir by waterpower and its work theory of stabilizing the level of water are introduced in this paper. The reliable performance of the weir is validated by an experiment. The precision of the water level stabilized by the device is high,enough to substitute other device used for stabilizing the level of water in lab. This device not only saves the area of the lab and the time for adjusting the water flux;but also increases greatly the precision of experimental simulation. It is of good practical value.
Abstract: A Particle Image Velocimetry is used to display the flow field of curved inlet cut off valve in this paper.Meanwhile, the RNG k-ε turbulence model is applied to simulate the turbulent flows in the symmetrical planes of curved and inclined inlet cut off valves.The control equations are solved in a body-fitted corrdinate by finite volume method with a staggered grid system.The computed results of curved inlet cut of valve are well in agreement with the experimental data,show that of curved inlet cut-off valve.The calculat ion results also show that the RNG k-ε turbulence model can be used to simulate the separated turbulent flows with eddies.
Abstract: The hydraulic conductivity is one of the most important parameters for describing the physical characteristics of porous media.The spatial variability of hydraulic conductivity has an important effect on water movement and solute transport in porous media.The methods based on spatial random fields fail to describe the spatial variation of hydraulic conductivity with multi-scales.Therefore a new method is developed in recent years on the basis of fractal theory,with which fractional Brown motion(fLm)and fractal Levy motion(fLm)are applied to study the variability of hydraulic conductivity without permanent integral scale.The main objective of this paper is to review the methods based on the fractal theory,and to analyze the relationship between the spatial variability of hydraulic conductivity and scale-effect of solute dispersivity and its application to describe water movement and solute transport.
Abstract: Groundwater flow in low permeability media can affeect the evolution of certain hydrological and geochemical systems and can impact the accumulations for petroleum and ores too.Such low permeability media are also important in the fields of waste disposal,engineering safety and environment changes.Although the Darcy's law is usually used as a fundamental as sumption in the studies of seepage flow theory for long period,its applicability has not been well tested in the range of very low pressure gradient in conforming with reality.It is more difficult to analyze the flow in low permeability media due to the complexity of hydrogeological conditions and the difficulties of measuring hydraulic head and sampling pore fluids.This paper reviews and summarizes studies on saturated seepage flow in low permeability media and discusses non-Darcy flow,coupled seep-age flow under multi factors,as well as two important nonhydraulic flow phenomena like osmosis and ultrafiltration.The problems of affecting and hindering analysis are discussed and some suggestions are also proposed for studies.
Abstract: Water resources scarcity and water environmental degradation have been the serious problems facing the world today,especially in developing countries.It is very urgent and significant to carry out the studies concerning water resources and water environmental carrying capacity to address the relationships and coordination between/of water system and human socio-economic system.This paper reviews the state of the art of the studies on water resources and water environmental carrying capacity,their concepts,characteristics,quantification and assessment methodology,and points out the deficiencies in current studies and the future research requirements.