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Water Science and Engineering 2012年第4期5卷 383-398页

作者： Jin-hai ZHENG Yi-xin YAN Chao-feng TONG Zhi-yi LEI Chi ZHANG State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai University College of Harbor Coastal and Offshore EngineeringHohai University

This paper presents a review of the state-of-the-art research and its applications developed at Hohai University relating to the hydrodynamic and morphological processes in the Yangtze Estuary. Longitudinal, lateral, and horizontal flow circulations have been revealed based on the measurements with acoustic Doppler current profilers （ADCP）. The hydrodynamic mechanism at diversion points as well as the changing patterns of flow and sediment flux in the Yangtze Estuary has been investigated through long-term data analysis. A field survey has been carried out to detect the saltwater intrusion from the North Branch to South Branch. Different numerical models of flow motion, sediment transport, and saltwater intrusion have been developed to simulate the complicated processes and to evaluate the effects of engineering projects. The morphological processes of wetlands over a time scale of decades have been analyzed with an established database. Ideas for further research on the bio-geomorphological model system and long-term evolution mechanisms are put forward.

关键词： Yangtze Estuary hydrodynamic process morphological process saltwater intrusion,Hohai University

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Event-triggered model-free adaptive control for a class of surface vessels with time-delay and external disturbance via state observer

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Journal of Systems Engineering and Electronics 2023年第3期34卷 783-797页

作者： CHEN Hua SHEN Chao HUANG Jiahui CAO Yuhan College of Science Hohai UniversityNanjing 210098China College of Mechanical and Electrical Engineering Hohai UniversityChangzhou 213022China hohai-Lille College Hohai UniversityNanjing 211100China

This paper provides an improved model-free adaptive control(IMFAC)strategy for solving the surface vessel trajectory tracking issue with time delay and restricted disturbance.Firstly,the original nonlinear time-delay system is transformed into a structure consisting of an unknown residual term and a parameter term with control inputs using a local compact form dynamic linearization(local-CFDL).To take advantage of the resulting structure,use a discrete-time extended state observer(DESO)to estimate the unknown residual factor.Then,according to the study,the inclusion of a time delay has no effect on the linearization structure,and an improved control approach is provided,in which DESO is used to adjust for uncertainties.Furthermore,a DESO-based event-triggered model-free adaptive control(ET-DESO-MFAC)is established by designing event-triggered conditions to assure Lyapunov stability.Only when the system’s indicator fulfills the provided event-triggered condition will the control input signal be updated;otherwise,the control input will stay the same as it is at the last trigger moment.A coordinate compensation approach is developed to reduce the steady-state inaccuracy of trajectory tracking.Finally,simulation experiments are used to assess the effectiveness of the proposed technique for trajectory tracking.

关键词： surface vessels event-triggered condition(ETC) discrete-time extended state observer(DESO) model-free adaptive control(MFAC) coordinate compensation

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Experimental study of the settling of twin spherical particles released side by side: The impact of particle size, fluid viscosity, initial spacing,and particle density

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International Journal of Sediment Research 2023年第1期38卷 83-96页

作者： Yang Xiao Jieqing Liu Pei Zhang Jian Zhou Dongfang Liang Zhihao Wang Taotao Zhang Saiyu Yuan Hongwu Tang State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai University Yangtze Institute for Conservation and Development Hohai University College of Water Conservancy and Hydropower Engineering Hohai University Institute of Water Science and Technology Hohai University School of Engineering Westlake University Department of Engineering University of Cambridge

The settling of solid particles in a fluid is an important process that needs to be considered in many fields of research. For example, the interactions among particles and between particles and the surrounding fluid are important topics in studying suspended sediment transport and water clarification. In this paper, the settling processes and interactions of twin spherical particles released side by side were experimentally studied. The Reynolds number varied in the range of 1-300, which is within the transition zone. Particle Tracking Velocimetry(PTV) and Particle Image Velocimetry(PIV) were utilized to capture the settlement trajectory, and provide insight into the flow fields around the particles. The influences of particle size, fluid viscosity, initial spacing, and particle density on the settling process were systematically investigated. The experimental results reveal that the initial spacing between the twin particles(l0*) and the Reynolds number(Re) are the two most important factors affecting particle settling. The interaction between particles comprises only repulsion when the initial spacing is small, while the density of particles has little effect on the final settling state when the initial spacing is not very small. The flow fields around different particles are similar for the same Re, leading to similar final settlement behaviors, except for the case of l0* = 0, when the influence of particle rotation cannot be ignored. Except for the case of l0* = 0, although the particle density has little effect on the final settling behavior, it affects the repulsive process during settling. The final repulsive distance between the twin particles is highly dependent on Re and l0*. Two critical Re values exist(～10 and ～100), where the repulsive distance is negatively correlated with Re when Re 100. However, the repulsive distance is always negatively correlated with l0*. These findings can improve understanding of more complex phenomena such as the part

关键词： Particle settlement Repulsion of particles Particle tracking velocimetry (PTV) Particle image velocimetry (PIV) Particle density

Mixed D-vine copula-based conditional quantile model for stochastic monthly streamflow simulation

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Water Science and Engineering 2024年第1期17卷 13-20页

作者： Wen-zhuo Wang Zeng-chuan Dong Tian-yan Zhang Li Ren Lian-qing Xue Teng Wu College of Water Resources and Hydrology Hohai UniversityNanjing 210098China Yellow River Research Center Hohai UniversityNanjing 210098China

Copula functions have been widely used in stochastic simulation and prediction of streamflow.However,existing models are usually limited to single two-dimensional or three-dimensional copulas with the same bivariate block for all months.To address this limitation,this study developed a mixed D-vine copula-based conditional quantile model that can capture temporal correlations.This model can generate streamflow by selecting different historical streamflow variables as the conditions for different months and by exploiting the conditional quantile functions of streamflows in different months with mixed D-vine copulas.The up-to-down sequential method,which couples the maximum weight approach with the Akaike information criteria and the maximum likelihood approach,was used to determine the structures of multivariate Dvine copulas.The developed model was used in a case study to synthesize the monthly streamflow at the Tangnaihai hydrological station,the inflow control station of the Longyangxia Reservoir in the Yellow River Basin.The results showed that the developed model outperformed the commonly used bivariate copula model in terms of the performance in simulating the seasonality and interannual variability of streamflow.This model provides useful information for water-related natural hazard risk assessment and integrated water resources management and utilization.

关键词： Stochastic monthly streamflow simulation Mixed D-vine copula Conditional quantile model Up-to-down sequential method Tangnaihai hydrological station

Experimental study on the stratum applicability and mechanisms of bubble-slurry for earth pressure balance shields

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Frontiers of Structural and Civil Engineering 2023年第9期17卷 1387-1399页

作者： Lu WANG Wei ZHU Yongjin QIAN College of Civil and Transportation Engineering Hohai UniversityNanjing 210098China Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering Hohai UniversityNanjing 210098China College of Environment Hohai UniversityNanjing 210098China

Soil conditioning is essential for addressing the stratum applicability problem of earth pressure balance(EPB)shields.Under high water pressures,EPB shields spew water and soil when excavating coarse-grained strata.Typically,foam combined with polymers and slurry is used to solve spewing.However,in current techniques,slurry,foam,and the other agents are mixed with soil separately,their synergistic effect is seldom realized.In this study,an anionic surfactant was used to foam in bentonite slurry to form bubble-slurry to maximize the synergy between bubbles and slurry.The slump,volume stability,and permeability test of bubble-slurry-conditioned sand was conducted to examine the conditioning effect,and the stratum applicability of bubble-slurry was determined from the perspective of permeability.It was found that the conditioning effect of bubble-slurry in coarse gravel soil was excellent and could expand the applicability of EPB shields.The main stabilization mechanism of bubble-slurry is that bentonite particles provide a space barrier for bubbles.And three seepage modes of bubble-slurry-conditioned sand were innovatively defined,and the occurrence conditions of the three seepage modes were analyzed according to the permeability coefficient of sand,initial dynamic shear force of bubble-slurry,and hydraulic gradient.

关键词： EPB shield bubble-slurry soil conditioning stability permeability

Stress corrosion cracking behaviors of RE-containing ME21 magnesium alloy processed by equal-channel angular pressing

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Journal of Rare Earths 2019年第1期37卷 88-94,M0005页

作者： Jinghua Jiang Qiuyuan Xie Mingshan Qiang Aibin Ma Evans-Kwesi Taylor Yuhua Li Dan Song Jianqing Chen College of Mechanics and Materials Hohai University Suqian Institute Hohai University

A commercial as-cast ME21 magnesium alloy containing rare-earth (RE) element was processed by equalchannel angular pressing to obtain fine-grained micro structure. Stress corrosion cracking (SCC) behaviors of the fine-grained samples were studied by slow-strain-rate testing in air, distilled water and Hanks’solution at the strain rate of 1×10^(-6) s^(-1). All samples show a relatively low SCC sensitivity in distilled water but a great SCC tendency in Hanks’ solution. The microscopic observations of the fracture surfaces and the side surfaces reveal obvious active anodic dissolution and hydrogen embrittlement cracks, which indicate the higher SCC susceptibility in Hanks'solution. The fine-grained microstructure with more crystal defects promotes the passivation process of the oxide film and restrains the hydrogen induced cracking of the ME21 magnesium alloy, leading to the higher general corrosion resistance as well as SCC resistance.

关键词： Magnesium alloy Stress corrosion cracking Equal-channel angular pressing Corrosion medium Fine-grained Rare earths

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Numerically investigating the crushing of sandstone by a tooth hob

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结构与土木工程前沿:英文版 2023年第6期17卷 964-979页

作者： Dongning SUN Baoning HONG Xin LIU Ke SHENG Guisen WANG Zhiwei SHAO Yunlong YAO Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering Hohai UniversityNanjing210098China Geotechnical Research Institute Hohai UniversityNanjing210098China Institute of Tunnel and Underground Engineering Hohai UniversityNanjing210098China

To investigate the mechanical process that occurs between rocks and tooth hobs,the crushing of sandstone with a tooth hob was simulated using reconstructed multi-mineral mesoscopic numerical models of various grain-sized sandstone samples.When a piece of sandstone is crushed by the tooth of a hob rolling at a constant speed,the resultant reaction forces of the sandstone on the tooth first hinder and then contribute to the rolling of the hob.The absolute value of the longitudinal reaction force is significantly higher than that of the lateral reaction force.Because the tooth was subjected to reaction forces from the sandstone,forces and moments were applied to the hob in order to keep the hob rolling.The applied forces were equal in value and opposite in direction to the reaction forces of the sandstone on the tooth.Three typical curves of the work done by the applied forces and moment were obtained,and the contribution of the applied lateral force and moment to the total work done for crushing sandstones was variable;however,no work was done by the applied longitudinal force.Moreover,the applied longitudinal force and total work were positively correlated with the strength of sandstone samples.The total work,applied forces,and moment increased with the maximum penetration depth of the tooth in the sandstone.

关键词： sandstone tooth hob crushing process reaction force numerical simulation

Impact of the Yellow River capture on the paleoenvironmental changes of Hongze Lake, China

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International Journal of Sediment Research 2023年第4期38卷 503-515页

作者： Hongwu Tang Ming Gao Saiyu Yuan Huiming Zhang Yang Xiao Fuxin Zhang Kun Zhang State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai University Key Laboratory of Hydrologic-Cycle and Hydrodynamic-System of Ministry of Water Resources Hohai University Institute of Water Science and Technology Hohai University

The Yellow River(YR) capture of the Huai River had a profound effect on the landscape evolution,ecology, and social development in China, disrupting the evolution of some vital shallow floodplain lakes.Because of the absence of lacustrine sediment provenance analysis, previous studies were inadequate in distinguishing the influence of YR capture on paleoenvironmental changes in these lakes, especially on landscape evolution, redox conditions, lake level changes, and organic productivity. The current study aims to use X-ray fluorescence-core scanning(XRF-CS) and multivariate statistics on a 9.8 m sediment core from Hongze Lake(HZL), China, to analyze the impact of the YR capture on the lake’s paleoenvironmental changes and the sediment provenance simultaneously. High-resolution images, magnetic susceptibility, and XRF-based multi-element data were obtained using a GEOTEK Multi-Sensor Core Logger. The calcium(Ca) content indicates the presence of YR sediment in HZL, given the high Ca content in YR sediment and the identification of mainly exogenous sources of Ca in HZL. The high values of Ca indicate that 48.7% of the sediment in the center of HZL is related to the YR’s incursion. Periods of higher Ca content coincide with periods of higher oxygenation levels of the lake(as indicated by the ratio of manganese to titanium) and lower organic content in the lake sediment(as indicated by the ratio of incoherent to coherent scatter). These analyses reveal that the YR’s capture of HZL significantly increased the lake’s oxygen level. Furthermore, the decrease in the organic content of sediment tends to be the result of the accelerated deposition caused by the YR. The decrease in Ca content coincides with an increase in lake levels(as indicated by magnetic susceptibility). Thus, it can be inferred that the embankment on the eastern side of HZL, built to increase lake storage, has reduced the incursion frequency of the YR.

关键词： Yellow River capture Paleoenvironmental reconstruction XRF-CS Hongze Lake

Recent progress in porous Mg-based foam preparation approaches:effect of processing parameters on structure and mechanical property

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Journal of Iron and Steel Research(International) 2022年第3期29卷 371-402页

作者： Solomon-Oshioke Agbedor Dong-hui Yang Jing Cao Jian-qing Chen Bassiouny Saleh Chao Qiu Lei Wang Jing-hua Jiang Ai-bin Ma College of Mechanics and Materials Hohai UniversityNanjing211100JiangsuChina Suqian Research Institute of Hohai University Suqian223814JiangsuChina Ocean and Offshore Engineering Research Institute of Hohai University Nantong226019JiangsuChina

Porous metals are a class of cellular materials with lightweight and unique mechanical,electrical,thermal,physical and acoustic characteristics.Magnesium and magnesium alloy foams have exhibited excellent advantages.In particular,open-cell Mg-based foams(porous Mg/Mg alloy foams)have been used for bioresorbable implants,CO_(2)trapping systems,filters,heat exchangers,absorbent panels and many other applications.While significant progress has been taken in producing porous Mg-based foams with good structure-property relations,but with a large number of different processing parameters,different mechanical properties and pore morphologies of each porous Mg-based foam,it is essential to understand the individual effects of each aspect of the parameters.Therefore,the present article summarized the effects of available processing parameters on the structure and mechanical properties of the porous Mg-based foams.Finally,the future perspectives to enhance the structure and properties of porous Mg/Mg alloy foams were discussed.

关键词： Porous Mg alloy Powder processing Sintering Liquid metal infiltration Mechanical property

Compression behavior of metal foams with real pore structures through CT scan images

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Journal of Iron and Steel Research(International) 2022年第11期29卷 1886-1897页

作者： Lei Wang Kai Jiang Dong-hui Yang College of Mechanics and Materials Hohai UniversityNanjing 211100JiangsuChina Suqian Research Institute of Hohai University Suqian 223814JiangsuChina

Based on the real pore structure obtained from computed tomography(CT)scan images,a three-dimensional(3D)model of the metal foam sample with specified porosity is established,and the model is compressed and simulated by finite element method with the simulation results compared with the experimental test results for validation.At the same time,based on the spatial distribution characteristics of cells extracted from 3D model construction,a widely used metal foam model with Voronoi pore structure or spherical pore structure was established and simulated under compression.The two compression simulation results with regular pore structure models were also compared with the experimental results and CT model results to study the influence of cell wall morphology on the compression performance of metal foams.The simulation results show that CT model agrees well with the experimental results and is more accurate than Voronoi pore or spherical pore model,which can provide a more reasonable option for investigation of metal foams.

关键词： Metal foam Computed tomography scan Three-dimensional reconstruction Cell wall morphology Compression performance