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Chen F.,Shanghai Water Engineering Design and Research Institute Co.
Advances in Science and Technology of Water Resources | Year: 2014

In the past years, there were some key technical problems in reinforcement of flood wall, such as ambiguous causes in analysis of dangerous situations, no unified standards for flood defense, contradictions of planning standards and current situations, mismatches of protective standards and urban development, unreasonable reinforcement scale, etc. In this paper, the examples of risk situations are collected to analyze the main factors that lead to the mentioned problems. Firstly, we present a study of the relationships among these various factors and then contrast planning standards with present status. In addition, further researches have been done which deconstruct the contradictions in current protected standards and analyze the reasons of unreasonable proposed scale for the reinforcement of floodwall. Main reasons of the dangerous situations include boundary conditions change, illegal operation of vessels, structural safety deficiencies, land subsidence, and engineering impact caused by projects that are adjacent to or pass through rivers. Various dangerous situations are caused by one or more factors; thus in order to raise the security levels in upstream regions, the standards of protection should be checked from overall defense standards which have been corrected by measured hydrological data. Furthermore, for ascertaining the principles of project scale of reinforcement, working conditions, hydrological features, the dangerous situation and the planning or standards evolution should be taken into account. At last, restrictive conditions should be settled on the shoreline of dock and ship lock. ©, 2014, Advances in Science and Technology of Water Resources. All right reserved. Source


Li L.,Shanghai Water Engineering Design and Research Institute Co. | Zhu J.,State Key Laboratory of Estuarine and Coastal Research
Shuikexue Jinzhan/Advances in Water Science | Year: 2016

According to the field data collected in the Changjiang Estuary in December 2011 and January 2012, there was a freshwater extension from the North Channel (NC) to the mouth and lower reaches of the North Branch (NB) where the water salinity was decreased during spring and the subsequent middle tides. However, the phenomenon was absent during the neap tides and subsequent middle tides. To reveal the origin of the freshwater in the lower reaches of the NB, We employed the well validated 3-D numerical model to reproduce the observed phenomenon. The numerical experiments were conducted and the freshwater flux decomposing method was used to investigate the underlying dynamic mechanism of the freshwater extension. We found that the freshwater in the NC extends to the NB mainly through its northern outlet (NONC) and neighboring shoals during spring and the subsequent middle tides due to the Lagrangian transports. Deepening of NONC facilitated the freshwater extension, and hindered the saltwater intrusion into the NB. In the contrast, the high-speed northerly winds would restrict the freshwater extension, while assist the saltwater intrusion into the NB. © 2016, Science Press. All right reserved. Source


Yuan R.,East China Normal University | Wu H.,East China Normal University | Zhu J.,East China Normal University | Li L.,Shanghai Water Engineering Design and Research Institute Co.
Journal of Marine Systems | Year: 2015

A three-dimensional numerical model was used to study the response time of the Changjiang (Yangtze) River plume to river discharge by artificially increasing the runoff over a short period and investigating the variation of salinity in the plume region. The time lagged between the change of river discharge and the change of salinity that reaches the 10% of the adjusted value is considered as the response time in this study. The response times in the plume region differed slightly when the river discharge during the spring tide and the neap tide was increased. Specifically, the response times near the river mouth and in the plume edge were ~. 1. days and more than 15. days, respectively. The brackish water volumes were also calculated to determine the variations in the plume extensions over time. A tracer was released to study the transport time from the Datong station to the East China Sea using the concept of water age. The tracer transport time ranged from 10. days near the river mouth to more than 50. days at the edge of the plume, which is much longer than the response time of the surface salinity. © 2015 Elsevier B.V. Source


Cui D.,Shanghai Water Engineering Design and Research Institute Co. | Liu X.,Shanghai Water Engineering Design and Research Institute Co.
Proceedings of the 11th (2014) Pacific/Asia Offshore Mechanics Symposium, PACOMS 2014 | Year: 2014

Due to dispersive errors, numerical dissipation of the advection terms may have a great influence on numerical solution accuracy of advection-diffusion issue. It is necessary to grasp numerical dissipation level before putting some scheme into use. Considering the lack of quantitative indicator on numerical dissipation, the quantitative indicator and research method were established in this paper. The method was successfully used to study the false diffusion law of QUICKEST discrete scheme and guild how to choose an appropriate discrete scheme in numerical simulation of salinity of Yangtze river estuary. The results show that the false diffusion coefficient could be applied to characterize the numerical dissipation level. The value of the false diffusion coefficient can be obtained according to the true dispersion effect. Copyright © 2014 by The International Society of Offshore and Polar Engineers. Source


Cui D.,Shanghai Water Engineering Design and Research Institute Co. | He X.,Shanghai Water Engineering Design and Research Institute Co. | Yang H.,Shanghai Water Engineering Design and Research Institute Co.
Advances in Science and Technology of Water Resources | Year: 2014

Considering the fact that quantitative indicator on numerical dissipation is lacking, in this paper the quantitative indicator and research method were given. The method is, namely, using generalized “false diffusive” coefficient of the certain indicators to measure the degree of numerical dissipation of a discrete format. The numerical value of the above method approximately equals to the same effect on the true diffusion of the diffusion coefficient. As to the true diffusion effect, the highly precise numerical value can be approximately obtained by the solution of the pure diffusion formulas. This method was successfully applied to third-order QUICKEST discrete scheme. The overall results show that false diffusion coefficient could be introduced to characterize the numerical dissipation level, whose value can be obtained by comparing the true diffusion effect. Source

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