Traceability Technology for Sudden Water Pollution Accidents in Rivers

The traceability technology for sudden water pollution accidents can be used for fast, accurate identification of a pollution source in the river. A correlation optimization model with the pollution source position and release time as its parameters is established based on hydrodynamic calculation and on the coupling relationship between forward concentration probability density and backward position probability density; and the solution of the model is realized by using a differential evolution algorithm (DEA). A coupled probability density method is to convert the traceability of a sudden water pollution accident into the optimization of two minimum values. This method is simple in principle and easy in solution, realizing the decoupling of parameter of the pollution source. The concept of gradient is introduced to the differential evolution algorithm, improving the efficiency of searching process. The proposed method of traceability was applied to the emergency demonstration project of the SNWDMRP. The results indicate that the model has good efficiency of traceability and high simulation precision and that traceability results have a certain guiding significance to the emergent regulation and control of sudden water pollution events in a river

Simulation Technology for Hydrodynamic and Water Quality in the Main Canal

The hydrodynamic and water quality simulation technology can be used for predicting the pollutant diffusion process after a sudden water pollution accident, and for analyzing the effect of emergency operation measures. The MRP features a long route, a variety of buildings, etc.; therefore, a set of hydrodynamic and water quality models that are applicable to the main canal of the MRP was independently developed based on 1-D open canal hydrodynamic and water quality theory and with various types of buildings as inner boundaries. Through calibration and verification, these models can be applied to the simulation of hydraulic and water quality response process under any operation conditions in the main canal of the MRP

Metamodel approach for reliability-based design optimization of a steel catenary riser

A reliability-based design optimization (RBDO) methodology is presented for the design of a steel catenary riser (SCR) under dynamic environmental loads. The purpose of this work is to optimize the cost of products subjected to probabilistic constraints. Searching for the optimal design of the riser in a wide range of design variables is computationally very expensive if time-consuming codes for dynamic analysis are necessary in the iteration process. In this study, the effectiveness of the proposed RBDO using a metamodel is firstly studied and validated through a beam test, then applied to the industrial dynamic optimization problem. The design variables of structures are assumed to be uncertain, and some other parameters such as loading and material properties are considered random. The performance function is approximated using metamodels to avoid time-consuming finite-element analysis during the optimization iteration. A single-loop method is used to decouple the double-loop RBDO problem. The reliability is finally confirmed through Monte Carlo simulations. According to the analysis, the presented methodology is more rational and realistic compared with deterministic optimization

Dynamic and Fatigue Analyses of Stress Joint for Deepwater Steel Catenary Riser

As the offshore industry continues to progress developments in deepwater, Steel Catenary Riser (SCR) offers great advantages over other risers. In order to provide the hang-off with sufficient stiffness, stress joint is used to connect the riser with platform. When stress joints are located at the top of a deep marine riser, it is greatly affected by both axial and bending stress due to great cyclic loading. So it is necessary to do some research on dynamic and local fatigue analyses for stress joint. In this work, global dynamic analysis for a SCR is performed firstly, then local boundary condition obtained from the previous analysis are applied to the stress joint FE model for time domain dynamic and multiaxial fatigue analysis. Results indicate that the stress level is far lower than yield limit of material and damage induced by fatigue needs more attention. Besides, the damage character of the two types of stress joints differs: for TSJ, the place where stress joint connects with riser is easy to occur fatigue damage; for SSJ, the most probable position is at the place where the end of inner sleeve pipe contacts with the riser body. Compared with SSJ, TSJ shows a higher stress level but better fatigue performance, and it will have a higher material cost. Considering various factors, designers should choose the most suitable type and also geometric parameters

Dynamic Optimization of Steel Catenary Risers Based on Reliability Using Metamodel

Reliability based design optimization (RBDO) of a steel catenary riser (SCR) using metamodel is investigated. The purpose of the optimization is to find the minimum-cost design subjecting to probabilistic constraints. To reduce the computational cost of the traditional double-loop RBDO, a single-loop RBDO approach is employed. The performance function is approximated by using metamodel to avoid time consuming finite element analysis during the dynamic optimization. The metamodel is constructed though design of experiments (DOE) sampling. In addition, the reliability assessment is carried out by Monte Carlo simulations. The result shows that the RBDO of SCR is a more rational optimization approach compared with traditional deterministic optimization, and using metamodel technique during the dynamic optimization process can significantly decrease the computational expense without sacrificing accuracy

Planning of River System Connection Project in Panggong District of Xiangyang

Panggong District, surrounded by the Han River on three sides, is close to Xiangyang Ancient City. It is the key area of strategic layout of Xiangyang’s urbanization development. The low-lying topography and high-level underground water with a lack of drainage channel and rainwater storage area cause a serious problem of drainage and waterlogging prevention in this region. A river system connection project was planned to solve this problem, in which new river systems were excavated and necessary gates and pumping stations were constructed to improve the capacity of drainage and waterlogging prevention of the region. Furthermore, the operation schemes of the connection project were determined in flood season and dry season, the project benefit was analysed, and related problems were discussed

Planning of River System Connection Project in Panggong District of Xiangyang

Panggong District, surrounded by the Han River on three sides, is close to Xiangyang Ancient City. It is the key area of strategic layout of Xiangyang’s urbanization development. The low-lying topography and high-level underground water with a lack of drainage channel and rainwater storage area cause a serious problem of drainage and waterlogging prevention in this region. A river system connection project was planned to solve this problem, in which new river systems were excavated and necessary gates and pumping stations were constructed to improve the capacity of drainage and waterlogging prevention of the region. Furthermore, the operation schemes of the connection project were determined in flood season and dry season, the project benefit was analysed, and related problems were discussed

Multiaxial fatigue analyses of stress joints for deepwater steel catenary risers

In the present study, the dynamic and fatigue characteristics of two types of stress joints are investigated under ocean environmental condition. Connected with the riser and the platform, stress joint at the vessel hang-off position should be one of the main critical design challenges for a steel catenary riser (SCR) in deepwater. When the riser is under a high pressure and deepwater working condition, the stress state for the joint is more complex, and the fatigue damage is easy to occur at this position. Stress joint discussed in this paper includes two types: Tapered Stress Joint (TSJ) and Sleeved Stress Joint (SSJ), and multiaxial fatigue analysis results are given for comparison. Global dynamic analysis for an SCR is performed first, and then the local boundary conditions obtained from the previous analysis are applied to the stress joint FE model for the later dynamic and multiaxial fatigue analysis. Results indicate that the stress level is far lower than the yield limit of material and the damage induced by fatigue needs more attention. Besides, the damage character of the two types of stress joints differs: for TSJ, the place where the stress joint connects with the riser is easy to occur fatigue damage; for SSJ, the most probable position is at the place where the end of the inner sleeve pipe contacts with the riser body. Compared with SSJ, TSJ shows a higher stress level but better fatigue performance, and it will have a higher material cost. In consideration of various factors, designers should choose the most suitable type and also geometric parameters

An Emergency Operation Model in Upstream Pools of the Accident Pool of the Middle Route of South-to-North Water Diversion Project

Considering the potential emergency accident in the Middle Route of South-to-North Water Diversion Project (MRP), previous studies required upstream pools of accident pool where accident occurs to maintain constant downstream level in the final state of emergency operation, which could cause large amount of abandoned water. In order to save water resources, an emergency operation model in upstream pools of the accident pool of the MRP was built, which allows downstream levels to rise by a certain amount in the final state, and can minimize the total abandoned water through allocating volumes in the upstream pools. This model could play an important role to determine reasonable emergency operation measures in the upstream pools