作者机构:
[Zhou, Wenzhe; Cheng, Yongzhou; Lin, Zhiyuan] Changsha Univ Sci & Technol, Sch Hydraul & Environm Engn, Changsha 410114, Peoples R China.;[Cheng, Yongzhou] Key Lab Water Sediment Sci & Water Disaster Preven, Changsha 410114, Peoples R China.
通讯机构:
[Yongzhou Cheng] S;School of Hydraulic and Environmental Engineering, Changsha University of Science & Technology, Changsha, 410114, China<&wdkj&>Key Laboratory of Water-Sediment Sciences and Water Disaster Prevention of Hunan Province, Changsha, 410114, China
摘要:
A plate system, composed of flat array is proposed to be one type of breakwater. At present, little research has been done on the wave elimination of the plate under long-period waves. The Reynolds-averaged Navier-Stokes (RANS) equations are treated based on three-dimensional closed RNG k-epsilon turbulence model and the governing equations are solved by VOF method. A numerical model of the interaction between wave and flat array breakwater is established to study the wave elimination performance of different wave period ang steep. The flow and vortex fields are solved to research the wave dissipation mechanism of breakwaters. Results show the wave transmission coefficient tends to increase with the increase of wave period. Wave transmitted coefficient are all less than 0.4 in this test, indicating that the flat array plate breakwater maintains a certain wave dissi-pation capacity for long-period waves. At the same period, the wave steepness change mainly affects the amount of water passing through the upper part of the flat plate, which has some influence on the way the breakwater dissipates energy. The plate spacing is the main wave energy dissipation area, which provides space for water exchange and effectively eliminate waves while reducing the amount of board. The results preliminarily demonstrated the potential application of flat plate array as a wave energy breakwater, but the flat plate parameter design and the interaction of waves and flat plates needs further research.
作者机构:
[Cheng, Yongzhou; Zheng, Yuwei; Xie, Huawei; Shi, Li] Changsha Univ Sci & Technol, Sch Hydraul & Environm Engn, Changsha 410114, Peoples R China.;[Cheng, Yongzhou] Key Lab Water Sediment Sci & Water Disaster Preven, Changsha 410114, Peoples R China.;[Xie, Huawei] Zhejiang Univ Water Resources & Elect Power, Sch Hydraul & Environm Engn, Hangzhou 310018, Peoples R China.
通讯机构:
[Cheng, YZ ] C;Changsha Univ Sci & Technol, Sch Hydraul & Environm Engn, Changsha 410114, Peoples R China.
关键词:
Vibration;Monopile foundation;Scour pit
摘要:
Offshore wind monopile foundations are subjected to strong wave current nonlinear effects and horizontal vi-bration loads caused by strong winds, waves, and rotating blades. In order to understand the rule of sediment movement around monopile under different vibration frequencies and amplitude, a cyclic loading test was carried out in the sand tank. The motion and migration rule of sediment particles around monopile under vi-bration action was observed by color tracer sand. The development process of the subsidence pit was qualita-tively described by comparing the typical moment photos of sediment particle movement on the bed's surface with time. The transition zone of sediment particles was observed by vertical cutting of the sand bed. Then, the relationship between the relative time scale T0 and the vibration intensity under pure vibration load is analyzed, and the relationship between the equilibrium settlement depth and the initial settlement rate is obtained. The experimental results show that under vibration loading, the densification of the sand bed around the monopile foundation along the loading direction and the phenomenon of ratchet convective movement is relatively strong, and the relative time scale of settlement shows a tendency to decrease with the increase of vibration intensity; the multi-stage alternating loading of vibration and wave-flow loading will result in the backfilling and widening of the scouring pits; the rise in the amplitude and the frequency of vibration under the joint action of wave-current -vibration will decrease the depth of the equilibrium scouring, and the width of scouring pits will increase significantly with the increase of amplitude, and the backfilling of the sand will be more evident with the in-crease of the frequency of vibration.
作者机构:
[Xu, Conghao] Key Lab Water Sediment Sci & Water Disaster Preven, Changsha 410114, Peoples R China.;[Xu, Conghao] Changsha Univ Sci & Technol, Sch Hydraul & Environm Engn, Changsha 410114, Peoples R China.;[Huang, Zhenhua] Univ Hawaii Manoa, Sch Ocean & Earth Sci & Technol, Dept Ocean & Resources Engn, Honolulu, HI 96820 USA.
关键词:
Foundation design;Pile group;Ripples;Sediment transport;Shore protection
摘要:
A pile breakwater is a row of closely-spaced piles, placed in a side-by-side arrangement, to dissipate wave energy and prevent coastal erosion. It is important to understand the local scour at a pile breakwater for its foundation design. This paper reports a set of wave-flume tests on the local scour around the piles in regular waves. A laser scanner was used to measure the change in the three-dimensional bed elevation. Five values of Keulegan-Carpenter number were examined in this study. Scour holes near the pile breakwater were developed due to the oscillatory jet flow through the gaps between adjacent piles, and sand ripples were observed on both sides of the structure. The migration of the sand ripples was either onshore or offshore, depending on the wave conditions. The maximum scour-hole depth had an exponential growth with the duration of wave attack, and the equilibrium depth was found to be deeper than that for a standalone pile. Both the scour-hole depth and length were found to be scaled by the pile diameter. The ripple length and steepness were in general agreement with recent empirical formulas in the literature in spite of the presence of a pile breakwater.
关键词:
Pervious concrete;Waste rubber;Resource recycling;Mechanical properties;DEM model
摘要:
The reuse of waste rubber has a profound impact on environmental protection and resource recy-cling. To evaluate the feasibility of adding waste rubber into pervious concrete, the effects of rub-ber content and particle size on the mechanical properties of pervious concrete are investigated through experiments and discrete element method (DEM) simulation. The compressive failure mode of pervious concrete gradually transits from tensile failure to shear failure with the increase of rubber content, showing a decrease in compressive strength, and the larger the particle size is, the stronger the attenuation effect on the strength is. Rubber particles play a role in isolating coarse aggregates from the cement matrix and form a weak bond with the matrix, showing a weak bridging effect in stress transmission at the left and right ends of the crack, so that the split-ting tensile strength of pervious concrete significantly decreases with the increase of rubber con-tent, and the weakening effect of coarse rubber on the splitting tensile strength is stronger than that of fine rubber. Due to the low strength of rubber itself and weak bonding with cement ma-trix, pervious concrete with high rubber content breaks in advance at the bottom of the midspan, resulting in the decline of flexural capacity, and it decreases more obviously with the increase of rubber size. Although the direct tensile strength of pervious concrete gradually decreases with the increase of rubber content, the addition of rubber improves the plasticity of pervious con-crete. Moreover, the plastic reinforcement effect of pervious concrete is the strongest when the rubber content reaches approximately 10%, and this toughening effect increases with the de-crease of rubber size. On the basis of experimental research, a universal DEM model considering rubber content and particle size is established, which can well predict the mechanical perfor-mance of rubberized pervious concrete in terms of strength, failure mode, elastic modulus and ul-timate strain.
期刊:
Stochastic Environmental Research and Risk Assessment,2023年37(2):639-650 ISSN:1436-3240
通讯作者:
Yuannan Long
作者机构:
[Long, Yuannan; Lv, Qian; Wen, Xiaofeng; Yan, Shixiong] Changsha Univ Sci & Technol, Sch Hydraul & Environm Engn, Changsha 410114, Peoples R China.;[Long, Yuannan; Wen, Xiaofeng] Key Lab Water Sediment Sci & Water Disaster Preve, Changsha 410114, Peoples R China.;[Long, Yuannan; Wen, Xiaofeng] Key Lab Dongting Lake Aquat Ecoenvironm Control &, Changsha 410114, Peoples R China.
通讯机构:
[Yuannan Long] S;School of Hydraulic and Environmental Engineering, Changsha University of Science & Technology, Changsha, China<&wdkj&>Key Laboratory of Water-Sediment Sciences and Water Disaster Prevention of Hunan Province, Changsha, China<&wdkj&>Key Laboratory of Dongting Lake Aquatic Eco-Environmental Control and Restoration of Hunan Province, Changsha, China
摘要:
Monthly streamflow forecasts have important practical applications in short-term water resources management, e.g., water allocation for different users, flooding prevention, and drought mitigation. This study focuses on developing categorical streamflow forecasts for flooding mitigation purpose, which can be used as a critical component in an early flood warning system. A Bayesian logistic regression approach is proposed to use antecedent streamflow and forecasted precipitation from General Circulation Models (GCMs) and derive the probability of streamflow greater than threshold streamflow. The logistic regression model is Hierarchical Bayesian Modeling that assumes Bernoulli distribution for monthly and Normal distribution for the parameters in the logistic function. To accommodate outliers in the modeling dataset, an additional parameter is added to the Bayesian modeling framework to make it a more robust approach. The Bayesian Logistic Regression is implemented in JAGS and posterior distributions of model parameters are estimated from Markov Chain Monte Carlo (MCM) chains. The proposed method is applied to a watershed in Hunan Province located in the middle south of China. Precipitation and streamflow data in the years 1960-2012 were used to estimate the model parameters' posterior distributions. The model's performance is tested for monthly streamflow data in the years 2013-2017, using one-month-ahead precipitation forecasts from GCMs. The model is superior to climatology, the reference model, in terms of the accuracy of hit rates. Potential improvement to the model is also discussed. Although the proposed method is demonstrated for the study area, it can be applied to other regions with similar applications.
关键词:
High-strength hydraulic concrete;Freeze-thaw cycles;Cyclic tensile load;Loading-unloading constitutive;DEM prediction model
摘要:
Hydraulic concrete structures in cold regions are vulnerable to freeze-thaw (FT) cycles, which will significantly weaken their ability to resist tensile load, thus threatening the safe operation of structures. Direct tensile properties of high-strength hydraulic concrete subjected to different FT cycles (0, 100, 200, 300 and 400 FT cycles) are investigated through experimental analysis and numerical simulation. The results show that the tensile strength, initial elastic modulus and ultimate strain of hydraulic concrete decrease linearly with the in-crease of FT cycles, and the cumulative rate of residual strain is independent of FT damage, but increases linearly with the increase of unloading strain. Based on FT damage caused by temperature and mechanical damage caused by external load, a cyclic tensile model considering FT effect is proposed. Moreover, the evolutions of principal strain, main crack width and internal microcrack of hydraulic concrete subjected to different FT cycles under cyclic tensile load are revealed by digital image correlation (DIC) and acoustic emission (AE) techniques. Based on experimental analysis, a DEM cyclic tensile prediction model considering loading-unloading consti-tutive and real aggregate is established to accurately describe the cyclic tensile response of hydraulic concrete subjected to different FT cycles.
摘要:
Microplastics have become a research hotspot in the environmental field owing to their persistence and complex ecological effects. Although microplastics have attracted public attention only recently, the microplastic pollution in lake, a unique water system characterized by their irreplaceable ecological value and special hydrodynamic conditions, were increasingly documented, calling for a summary of the most recent advance in this research area. Therefore, the sampling and analysis methods, occurrence, sources, and ecological effects of microplastics in lakes were summarized in this review. Various types of plastics are produced and used in large quantities for different purposes, resulting in microplastic pollution being widespread in lakes worldwide, albeit with different levels and characteristics. Microplastics constantly migrate and transform in lake ecosystems, exerting impacts on ecological, including pollution diffusion and biological toxicity. This review focused on the migration of microplastics in water and food chains, which is a different perspective than that considered in previously published reviews. This review also discussed the limitations of existing studies and made recommendations. Future research directions should include the following: 1) improving the baseline database of microplastic pollution in lakes; (2) unifying the sampling and laboratory analysis methods; (3) exploring the quantitative analysis methods of the sources, transportation, and fate of microplastics; (4) considering more factors to explore the effects of microplastics on lake ecosystems.
通讯机构:
[Long, YN ] C;Changsha Univ Sci & Technol, Sch Hydraul & Environm Engn, Changsha 410114, Peoples R China.;Key Lab Dongting Lake Aquat Ecoenvironm Control &, Changsha 410114, Peoples R China.;Key Lab Water Sediment Sci & Water Disaster Preven, Changsha 410114, Peoples R China.
关键词:
water level;discharge;Dongting Lake;water surface slope
摘要:
Abstract: The hydrological characteristics of the river–lake connecting section are determined by their interaction and studying them can help to understand the changing relationship between these two water bodies over time. The Lujiao–Luosan section is the connecting section of Dongting Lake and the Yangtze River, and the hydrological data for this section over the past 70 years has been analyzed. It has been found that the lowest water level is consistently rising at the same discharge at Chenglingji station, which is the joint point of Dongting Lake and the Yangtze River. While this could alleviate the drought situation in the Dongting Lake area during dry seasons, it could pose a more significant flood-control challenge during high water levels in the flood season. The water surface slope shows a decreasing trend especially during the dry season, except for the high flood period (July–September), which indicates that the water slope in the connecting section of Dongting Lake has become flatter. The backwater effect of the Yangtze River on Dongting Lake becomes increasingly stronger as the water surface slope difference between the Chenglingji–Luoshan section and the Lujiao–Chenglingji section changes from negative to positive between January and April. Keywords: water level; discharge; Dongting Lake; water surface slope
通讯机构:
[Zhiling Liao; Shaowu Li] S;State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin University, Tianjin, 300072, China<&wdkj&>The Lyell Centre for Earth and Marine Science and Technology, Institute for Infrastructure and Environment, Heriot-Watt University, Edinburgh, EH14 4AS, UK<&wdkj&>State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin University, Tianjin, 300072, China
关键词:
Long wave;Coral reef;Energy transfer;SWASH;Breakpoint forcing;Radiation stress
作者机构:
[Zhao, Yuelong; Zhang, Peng; Fan, Yali] Taiyuan Univ Technol, Coll Environm Sci & Engn, Taiyuan 411201, Peoples R China.;[Zhang, Peng] Shanxi Normal Univ, Upgrading Off Modern Coll Humanities & Sci, Linfen 041000, Peoples R China.;[Zhang, Peng; Zhang, Wei] Hunan Univ Sci & Technol, Coll Civil Engn, Xiangtan 411201, Peoples R China.;[Zhang, Wei] Changsha Univ Sci & Technol, Coll Hydraul Engn, Changsha 410114, Peoples R China.
通讯机构:
[Wei Zhang; Peng Zhang] C;College of Civil Engineering, Hunan University of Science and Technology, Xiangtan 411201, China<&wdkj&>College of Hydraulic Engineering, Changsha University of Science & Technology, Changsha 410114, China<&wdkj&>College of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan 411201, China<&wdkj&>Upgrading Office of Modern College of Humanities and Sciences of Shanxi Normal University, Linfen 041000, China<&wdkj&>College of Civil Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
摘要:
Abstract: In this study, CTS-GSH was prepared by grafting thiol (–SH) groups onto chitosan (CTS), which was characterized through Fourier Transform Infrared (FT-IR) spectra, Scanning Electron Microscopy (SEM) and Differential Thermal Analysis–Thermogravimetric Analysis (DTA-TG). The performance of CTS-GSH was evaluated by measuring Cr(VI) removal efficiency. The –SH group was successfully grafted onto CTS, forming a chemical composite, CTS-GSH, with a rough, porous and spatial network surface. All of the molecules tested in this study were efficient at removing Cr(VI) from the solution. The more CTS-GSH added, the more Cr(VI) removed. When a suitable dosage of CTS-GSH was added, Cr(VI) was almost completely removed. The acidic environment at pH 5–6 was beneficial for the removal of Cr(VI), and at pH 6, the maximum removal efficiency was achieved. Further experimentation showed that with 100.0 mg/L CTS-GSH for the disposal of 5.0 mg/L Cr(VI) solution, the removal rate of Cr(VI) reached 99.3% with a slow stirring time of 8.0 min and sedimentation time of 3 h; the presence of four common ions, including Mg2+, Ca2+, SO42− and CO32−, had an inhibitory effect on CTS-GSH’s ability to remove Cr(VI) from the aqueous solution, and more CTS-GSH was needed to reduce this inhibiting action. Overall, CTS-GSH exhibited good results in Cr(VI) removal, and thus has good potential for the further treatment of heavy metal wastewater. Keywords: hexavalent chromium; chitosan; reduced glutathione; chelating agent; amidation reaction; flocculation
通讯机构:
[Long, YN ] ;Changsha Univ Sci & Technol, Sch Hydraul & Environm Engn, Changsha 410114, Peoples R China.
关键词:
Dongting Lake Basin;Data -scarce area;Coupled hydrological and hydrodynamic;models;Streamflow simulation;Lake water balance
摘要:
Study region: The Dongting Lake Basin is a typical regional study in humid southern China with data-scarce areas. Study focus: This study improved the streamflow simulation by coupling hydrological and hydrodynamic models and considering water yields in data-scarce areas. We constructed a soil and water assessment tool (SWAT) hydrological model of the Dongting Lake Basin to simulate the streamflow in the data-scarce areas, which was further coupled into the MIKE21 hydrodynamic model as additional boundary conditions. New hydrological insights: The results showed that the relative error of streamflow simulation was reduced from 24.64 % to 10.50 % in the coupled hydrological-hydraulic model over the singular hydrodynamic model, which also indirectly verified the results of streamflow simulation in the data-scarce area. Based on the coupled model, the annual water yields in the data-scarce areas were estimated to be 38.95 x 109 m3, representing 15.13 % of the yearly water yields in the basin. The water yields in the data-scarce areas showed a seasonal variation, which was concentrated from April to July. The monthly water balance error of the Dongting Lake Basin was significantly reduced (57.42 %) when considering the water yields in data-scarce areas. The model-coupling approach in this study can be applied to other data-scarce areas to improve streamflow simulation.
作者机构:
College of Environmental Science and Engineering, Hunan University, Changsha 410082, P. R. China;Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082, P. R. China;[Wenqian Chen] Department of Pharmacy, National University of Singapore, S9, 4 Science Drive 2, Singapore 117544, Singapore;[Chao Lei] School of Hydraulic Engineering, Changsha University of Science & Technology, Changsha 410114, P. R. China;[Qian Guo; Binbin Huang] College of Environmental Science and Engineering, Hunan University, Changsha 410082, P. R. China<&wdkj&>Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082, P. R. China
通讯机构:
[Binbin Huang] C;College of Environmental Science and Engineering, Hunan University, Changsha 410082, P. R. China<&wdkj&>Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082, P. R. China
摘要:
The separation of photogenerated charges is vital for photocatalysis. Here, we report a wireless photoelectrochemical strategy for efficient charge separation on an optoelectronic synergy-driven nanoparticulate semiconductor. Using g-C3N4/Fe–TiO2 as model semiconductor nanoparticles, an advanced oxidation process (AOP) for water remediation was established with the activity and O2•– photogeneration quantum efficiency being significantly improved (i.e., 9.7 times compared to conventional photoelectrocatalysis and 5.9 times that of photocatalysis, respectively). More importantly, this strategy has a wide range of applications for the removal of different refractory organic pollutants with a strong tolerance for a supporting electrolyte. The extraordinary catalytic performance was attributed to a synergistic effect between photochemistry and electrochemistry on the particle surface, where numerous nanobipolar electrodes were generated under an electric field to trigger the reduction of electrogenerated O2 to form reactive oxygen species. This work provides a promising AOP strategy of a photoelectrochemical-driven nanoparticulate semiconductor for challenging water remediation.
关键词:
special ordered set of type 2;monthly hydropower scheduling;spillage controllable
摘要:
This study introduces a novel approach for optimizing the monthly hydropower scheduling of cascaded reservoirs by employing a special ordered set of type 2 (SOS2) formulation within a mixed integer linear programming (MILP) model. The proposed method linearizes the relationships between hydropower output, spillage, storage, and outflow, enabling controllable spillage. The objective is to minimize spillage, maximize firm hydropower output, and maximize energy production, all in priority while considering complex constraints such as reservoir storage and discharge bounds, upstream-downstream relationship, and water balance. The approach is applied to four cascaded reservoirs on the Lancang River. Results indicate that the SOS2 formulation effectively minimizes spillage, maximizes hydropower generation, and ensures maximum firm power output. Comparisons across different gridding resolutions reveal that more grid points yield greater benefits but with a longer solution time. Furthermore, a comparison with the Successive Quadratic Programming (SQP) method highlights the superior performance of the SOS2 model in terms of objective improvement and solution efficiency. This research offers valuable insights into optimizing monthly hydropower scheduling for cascaded reservoir systems, enhancing operational efficiency and decision-making in water resources management.
期刊:
Water Resources Management,2023年37(12):4933-4948 ISSN:0920-4741
通讯作者:
Long, YN
作者机构:
[Long, Yuannan; Zheng, Moruo; Long, YN; Yan, Shixiong] Changsha Univ Sci & Technol, Sch Hydraul & Environm Engn, Changsha 410114, Peoples R China.;[Long, Yuannan; Long, YN] Key Lab Dongting Lake Aquat Ecoenvironm Control &, Changsha 410114, Peoples R China.;[Long, Yuannan; Long, YN] Key Lab Water Sediment Sci & Water Disaster Preven, Changsha 410114, Peoples R China.;[He, Huaiguang] Hunan Inst Water Resources & Hydropower Res, Changsha 410007, Peoples R China.
通讯机构:
[Long, YN ] C;Changsha Univ Sci & Technol, Sch Hydraul & Environm Engn, Changsha 410114, Peoples R China.;Key Lab Dongting Lake Aquat Ecoenvironm Control &, Changsha 410114, Peoples R China.;Key Lab Water Sediment Sci & Water Disaster Preven, Changsha 410114, Peoples R China.
关键词:
Onset and demise;Rainy season;Xiang River Basin;Cumulative rainfall deficit;Soil moisture
摘要:
This study examines potential changes in the summer rainy season of a watershed, using a cumulative rainy deficit curve to define the onset and demise of the rainy season. Historical daily rainfall data from 41 gauge stations within the Xiang River Basin in 1960-2017 were analyzed. Results indicate that the climatology of the onset date is Julian day 72 and the climatology of the demise date is Julian day 236. There is, however, a difference between the two segments, e.g., 1960-1989 and 1990-2017. The median rainy season duration in 1990-2017 is 138 days. This is larger than that of 1960-1989, which is 120 days. There is a statistically significant correlation between the onset date of the rainy season and the duration of the rainy season. Daily soil moisture estimates were derived from satellite remote sensing data. The averaged soil moisture during the rainy season is much higher than that of the non-rainy season. To examine the difference in quick flow between rainy and non-rainy season, baseflow separation was applied to daily streamflow time series. Result reveals the median of weekly quick flow in rainy season is 1316 cms, which is 5.7 times that of the weekly quick flow in non-rainy season. Different mechanisms that drive spring and summer rainfall, as well as potential use of the results in water management, are discussed.