Abstract: Computations of steady shallow water flows are often perceived to be more difficult than unsteady ones due to low-rate convergence to steady states. This paper explores the possibility of utilizing five methods from CFD to accelerate the convergence, with some elaborate modifications peculiar to water flows. Based on numerical experiments, local time-stepping, redidual smoothing, and multigrid methods are recommended, in conjunction with the use of a critical value of CFL number determined through trial computations. By choosing an appropriate approach for a specific problem, a 30%-50% or even larger reduction in computational effort can be achieved.
Abstract: This paper presents that parameter-control inverse problems for parabolic-type equation and for Poisson equation can be solved respectively by Pulse pectrum Technique (PST) and BEM-optimization method. The solution procedures are formulated and numerical algorithms are given in the paper. The two algorithms have been applied respectively to invert the permeability coefficient of Xinanjiang dam foundation before and after being sthengthened by grouting. Numerical results show that PST and BEM-optimization method are valid for solving parameter-control inverse problems and can be applied to invert the permeability coeihcient of dams and their foundations. The advantages of the two methods are that they need much less additional informations and much less drilling and sampling work,so as to save much investment.
Abstract: The principle and methods of hierarchical analysis for large-scale system are applied to solve the practical problems of optimal planning and operation for water supply in Beijing-Tianjin-Tangshan (JJT) area water resources system. A three-level hierarchical model for water resources planning and three-level hierarchical simulation model have been established. Simulation technique combined with optimization methods is presented. On the basis of simulation for 40 alternatives, among them 20 best alternatives are comprehensively assessed and are arranged in the order of priority by means of a developed JJT water resources decision support system and specific proposals are presented.
Abstract: To solve the problems of low dependability of irrigation and less efficient operation of irrigation projects in pumping and storage irrigation systems, this paper presents an optimal operation model for a typical system in South Cnina. The model consists of a multi-dimension dynamic programming model, a simulation model, and some other optimization models, which can be used to provide optimal allocation ofirrigation water in time and space effectively. The case study has confirmed that the application of the model can increase dependabilites of irrigation and economic beaifits of the irrigation projects. The model provides a new way of increasing irrigation benifits for the similar systems.
Abstract: The new relationship of the height of dunes on alluvial bed is presented. The law of alluvial resistance in the transition regime is found. The comparisons among six important relationships of alluvial resistance are made. Einstein's and Ning qian's relationships are suitable for sandy rivers only in transition regime. Changhua Li's relationship can be applied to sandy rivers in the lower and transition regimes. Engelund's equations are a mean situation for sandy channels except for very fine sand and gravel bed and the transition regimes, it is not suitable for θ*'>1.96. Hayashi's equation is not suitable for sandy rivers with smaller slope. The author's resistance equaltions can be used in all of the three regimes, various sediment diameter and flow depth, its verification shows that the average error of calculated flow depths is very small.
Abstract: Characteristics of fluvial processes of the Lower Yellow River are analysed, and a review of three mathematical models used in the planning and design of the Lower Yellow River is presented. Features of these models and some disadvantages which should be improved are outlined. Finally, some suggestions about the further improvement of mathematical models used in the Lower Yellow River are put forward.
Abstract: In 1991,the heaviest flood occured in Taihu basin since 1954. The rainfall intensity in the norther n part and water level in Taihu Lake were both higher than those in 1954, brought about severe damages to the Suzhou-Wuxi-Changzhou regions. The characteristics of rainfall and flood are illustrated. The reasons of disaster are analyzed and the measures of flood and water logging control are also discussed.
Abstract: It is the first time that concentration of organic acid (formic acid and acetic acid in precipitation for Lanzhou City is continuously determined and studied by IC method. The results show that organic acid accounts for 6.88 percent of negation ion and 2.50 percent of total ion in precipitation for the region.The ion concentration range 0.31-1.63 (mg/L) for formic acid and 0.50-0.91 (mg/L) for acetic acid. The balance condition between negative ion and positive ion has been improved after measuring orga nic acid.
Abstract: Three approaches for determining parameters of the watershed concentration flow models are suggested by using hydrological or geographical data. The theory and method for determining parameters of the Naah model, which is only according to outflow data of the concentration Bow system, are discussed in detail, and some examples are also given in this paper.
Abstract: The key of large-scale system optimization is dimension reducing of models. The mixed-model is a method of dimension reducing by means of decomposing the total system into several sub-systems with loose inter-connections. The principies of the model construction, the classification, the characteristics and the optimal methods of the mixed model are summarized theoreticaly in this paper. It shows thatthe mixed model is useful applicated in the large water resources systems and irrigation or drainage systems with complicated structures and multiple functions.
Abstract: This paper reviews harnessing of the Lower Yellow River based on the characteristics of hyperconcentrated flows, including the tendency of water and sediment changes in the river, transport features of hyper-concentrated flows resistance properties laws of river processes, relationships between river channel geometries and incoming water and sediment, optimal composition of water and sediment to remodel the wide and shallow course of the Lower Yellow River, operation criteria to regulate water and sediment in reservoirs, harnessing measures, etc. when the harnessing is realized, the deposition in the Lower Yellow River can be descreased significantly, the water used for transporting sediment can be saved largely, the water resources can be utilized fully, and a new narrow, deep and stable channel will be formed.