To better understand the complex process of wave transformation and associated hydrodynamics over various fringing reef profiles, numerical experiments were conducted with a one-dimensional （1D） Boussinesq wave mode...To better understand the complex process of wave transformation and associated hydrodynamics over various fringing reef profiles, numerical experiments were conducted with a one-dimensional （1D） Boussinesq wave model. The model is based on higher-order Boussinesq equations and a higher-accuracy finite difference method. The dominant energy dissipation in the surf zone, wave breaking, and bottom friction were considered by use of the eddy viscosity concept and quadratic bottom friction law, respectively. Numerical simulation was conducted for a wide range of wave conditions and reef profiles. Good overall agreement between the computed results and the measurements shows that this model is capable of describing wave processes in the fringing reef environment. Numerical experiments were also conducted to track the source of underestimation of setup for highly nonlinear waves. Linear properties （including dispersion and shoaling） are found to contribute little to the underestimation; the low accuracy in nonlinearity and the ad hoc method for treating wave breaking may be the reason for the problem.展开更多
The main objective of the present study is to introduce new empirical equations for the determination of breach geometrical dimensions and peak outflow discharge(Q_(p)).Therefore,a historic failure database of 109 emb...The main objective of the present study is to introduce new empirical equations for the determination of breach geometrical dimensions and peak outflow discharge(Q_(p)).Therefore,a historic failure database of 109 embankments was collected and examined.The most important factors that affect the breach evolution,including grading size,hydraulic,and outflow characteristics are also studied.Some of the parameters used for the determination of Q_(p) and average breach width(Bave)have a significant effect on the erosion process,but they are less reflected in the technical literature.To study the behavior of noncohesive soils during overtopping,15 physical tests were performed at the laboratory,and the effects of interfering parameters were investigated.The experimental output hydrograph was used to simulate the hydrographs resulting from the failure of real dams,and recent artificial intelligence techniques along with linear and nonlinear regression models were employed.The area-time analysis of the laboratory hydrographs shows that the soil particle size and the characteristics of reservoir-basin significantly affect the rate of breach formation and outflow discharge.New relationships are introduced,based on the breach characteristics,by a combination of historical and experimental data,as well as case studies conducted on the hypothetical failure of 10 operational dams.The mathematical model is also used to simulate the process of breach evaluation.Based on statistical indices,comparison of the results,and sensitivity analysis,the developed equations can better express the susceptibility of materials to erosion and their application can minimize downstream vulnerabilities.展开更多
The wave-induced setup and circulation in a two dimensional horizontal(2DH)reef-lagoon-channel system is investigated by a non-hydrostatic model.The simulated results agree well with observations from the laboratory e...The wave-induced setup and circulation in a two dimensional horizontal(2DH)reef-lagoon-channel system is investigated by a non-hydrostatic model.The simulated results agree well with observations from the laboratory experiments,revealing that the model is valid in simulating wave transformation and currents over reefs.The effects of incident wave height,period,and reef flat water depth on the mean sea level and wave-driven currents are examined.Results show that the distributions of mean sea level and current velocities on the reef flat adjacent to the channel vary significantly from those in the area close to the side walls.From the wave averaged current field,an obvious alongshore flux flowing from the reef flat to the channel is captured.The flux from the reef flat composes the second source of the offshore rip current,while the first source is from the lagoon.A detailed momentum balance analysis shows that the alongshore current is mainly induced by the pressure gradient between the reef flat and the channel.In the lagoon,the momentum balances are between the pressure and radiation stress gradient,which drives flow towards the channel.Along the channel,the offshore current is mainly driven by the pressure gradient.展开更多
A concept is introduced in this article which has strong practical impact for computer aided system configuration. System configuration is a cumbersome and fault sensitive task while setting up systems in a broad rang...A concept is introduced in this article which has strong practical impact for computer aided system configuration. System configuration is a cumbersome and fault sensitive task while setting up systems in a broad range of business applications like ERP （enterprise resource planning） and other workflow-systems. Given a generic process or workflow model in YAWL-notation （yet another workflow language） or any other process modeling language like business process model and notation or WFMC （workflow management coalition）, it could be stated that, by using a set of reduction rules as introduced, it is possible to generate a hierarchically structured tree of sub graphs of the workflow graph-representation. According to the notation used, authors call these sub graphs facts. The tree structure of the graph-representation on one hand and the logical relation between the branches and leafs of the tree on the other can be utilized to create a set of constraints and dependencies among the single facts. Some researchers showed that the nested branches can be associated to （predefined） questions with respect to the configuration of a workflow management system, for instance an ERP-application. They presented an algorithm which dynamically sorts the questions and answers in a maximum efficient configuration path, while working through the corresponding questionnaire. By combining the different elements as facts, constraints on questions, and configuration space, it is thus possible to algorithmically generate the efficient structured and interactive questionnaire for the configuration of workflow systems and algorithmically check the consistency （dead lock free, free of synchronization structural conflict） of the underlying workflow model. The concept was tested in the prototype of the interactive questionnaire for configuration of the web-service based ERP-Application Posity.展开更多
基金supported by the National Natural Science Foundation of China(Grants No.51009018 and 51079024)the National Marine Environment Monitoring Center,State Oceanic Administration,P.R.China(Grant No.210206)
文摘To better understand the complex process of wave transformation and associated hydrodynamics over various fringing reef profiles, numerical experiments were conducted with a one-dimensional （1D） Boussinesq wave model. The model is based on higher-order Boussinesq equations and a higher-accuracy finite difference method. The dominant energy dissipation in the surf zone, wave breaking, and bottom friction were considered by use of the eddy viscosity concept and quadratic bottom friction law, respectively. Numerical simulation was conducted for a wide range of wave conditions and reef profiles. Good overall agreement between the computed results and the measurements shows that this model is capable of describing wave processes in the fringing reef environment. Numerical experiments were also conducted to track the source of underestimation of setup for highly nonlinear waves. Linear properties （including dispersion and shoaling） are found to contribute little to the underestimation; the low accuracy in nonlinearity and the ad hoc method for treating wave breaking may be the reason for the problem.
文摘The main objective of the present study is to introduce new empirical equations for the determination of breach geometrical dimensions and peak outflow discharge(Q_(p)).Therefore,a historic failure database of 109 embankments was collected and examined.The most important factors that affect the breach evolution,including grading size,hydraulic,and outflow characteristics are also studied.Some of the parameters used for the determination of Q_(p) and average breach width(Bave)have a significant effect on the erosion process,but they are less reflected in the technical literature.To study the behavior of noncohesive soils during overtopping,15 physical tests were performed at the laboratory,and the effects of interfering parameters were investigated.The experimental output hydrograph was used to simulate the hydrographs resulting from the failure of real dams,and recent artificial intelligence techniques along with linear and nonlinear regression models were employed.The area-time analysis of the laboratory hydrographs shows that the soil particle size and the characteristics of reservoir-basin significantly affect the rate of breach formation and outflow discharge.New relationships are introduced,based on the breach characteristics,by a combination of historical and experimental data,as well as case studies conducted on the hypothetical failure of 10 operational dams.The mathematical model is also used to simulate the process of breach evaluation.Based on statistical indices,comparison of the results,and sensitivity analysis,the developed equations can better express the susceptibility of materials to erosion and their application can minimize downstream vulnerabilities.
基金The Key Project of NSFC-Shangdong Joint Research Funding under contract No.U1906230the Fundamental Research Funds for the Central Universities under contract No.B200202064+1 种基金the National Natural Science Foundation of China under contract Nos 41930538 and 51879096Marine Science and Technology Innovation Project of Jiangsu Province under contract No.HY2018-15。
文摘The wave-induced setup and circulation in a two dimensional horizontal(2DH)reef-lagoon-channel system is investigated by a non-hydrostatic model.The simulated results agree well with observations from the laboratory experiments,revealing that the model is valid in simulating wave transformation and currents over reefs.The effects of incident wave height,period,and reef flat water depth on the mean sea level and wave-driven currents are examined.Results show that the distributions of mean sea level and current velocities on the reef flat adjacent to the channel vary significantly from those in the area close to the side walls.From the wave averaged current field,an obvious alongshore flux flowing from the reef flat to the channel is captured.The flux from the reef flat composes the second source of the offshore rip current,while the first source is from the lagoon.A detailed momentum balance analysis shows that the alongshore current is mainly induced by the pressure gradient between the reef flat and the channel.In the lagoon,the momentum balances are between the pressure and radiation stress gradient,which drives flow towards the channel.Along the channel,the offshore current is mainly driven by the pressure gradient.
文摘A concept is introduced in this article which has strong practical impact for computer aided system configuration. System configuration is a cumbersome and fault sensitive task while setting up systems in a broad range of business applications like ERP （enterprise resource planning） and other workflow-systems. Given a generic process or workflow model in YAWL-notation （yet another workflow language） or any other process modeling language like business process model and notation or WFMC （workflow management coalition）, it could be stated that, by using a set of reduction rules as introduced, it is possible to generate a hierarchically structured tree of sub graphs of the workflow graph-representation. According to the notation used, authors call these sub graphs facts. The tree structure of the graph-representation on one hand and the logical relation between the branches and leafs of the tree on the other can be utilized to create a set of constraints and dependencies among the single facts. Some researchers showed that the nested branches can be associated to （predefined） questions with respect to the configuration of a workflow management system, for instance an ERP-application. They presented an algorithm which dynamically sorts the questions and answers in a maximum efficient configuration path, while working through the corresponding questionnaire. By combining the different elements as facts, constraints on questions, and configuration space, it is thus possible to algorithmically generate the efficient structured and interactive questionnaire for the configuration of workflow systems and algorithmically check the consistency （dead lock free, free of synchronization structural conflict） of the underlying workflow model. The concept was tested in the prototype of the interactive questionnaire for configuration of the web-service based ERP-Application Posity.
