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Numerical simulations of morphological changes in barrier islands induced by storm surges and waves using a supercritical flow model

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Frontiers of Structural and Civil engineering 2014年第1期8卷 57-68页

作者： Soumendra Nath KUIRY Yan DING Sam S Y WANG Environmental & Water Resources engineering Division Department of Civil Engineering lndian Institute of Technology Madras Tamil Nadu 600036 India National Center for Computational Hydroscienee and engineering The University of Mississippi University MS 38677 USA

In this paper, an advanced explicit finite volume flow model in two-dimensions is presented for simulating supercritical coastal flows and morphological changes in a tidal/coastal inlet and barrier islands due to storm surges and waves. This flow mode/ is coupled with existing wave-action mode/and sediment transport mode/. The resulting integrated coastal process model is capable of simulating flows induced by extreme conditions such as waves, surge tides, river flood flows, etc., and morphological changes induced by rapid coastal currents and waves. This developed supercritical ftow model is based on the solution of the conservative form of the nonlinear shallow water equations with the effects of the Coriolis force, uneven bathymetry, wind stress, and wave radiation stresses. The forward Euler scheme is used for the unsteady term; and the convective term is discretized using the Godunov-type shock- capturing scheme along with the HLL Riemann solver on non-uniform rectilinear grids. The accuracy of the developed model is investigated by solving an experimental dam-break test case. Barrier island breaching, overflow and overwash due to severe storm attack are simulated and the predicted morphological changes associated to the events are analyzed to investigate the applicability of the model in a coast where all the physical forces are present.

关键词： coastal inlet coastal process modeling supercritical flow sediment transport barrier islands

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A miniature pump with a fluid dynamic bearing

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Science China(Technological Sciences) 2012年第3期55卷 795-801页

作者： LUO XianWu JI Bin ZHUANG BaoTang ZHU Lei LU Li XU HongYuan State Key Laboratory of Hydro Science and engineering Tsinghua UniversityBeijing 100084China Beijing Institute of Control engineering Beijing 100190China China Institute of Water Resources and Hydropower Research Beijing 100038China

This paper describes the development of a miniature pump having an impeller with an exit diameter of 24 mm supported with the motor rotor by a fluid dynamic *** verify that the miniature pump is stable and quiet for rotational speeds larger than 4000 *** three-dimensional turbulent flow in the entire pump flow passage and the laminar flow in the fluid dynamic bearing were then simulated *** average pump performance was well predicted by the *** the tests and the simulations show that there is no obvious Reynolds effect for the miniature pump within the tested range of rotational *** numerical results also show that the bearing capacity of the fluid dynamic bearing increases with the pump rotor rotational speed and the eccentricity ratio of the journal to the *** pump is very compact,so it is a promising device for surgical use.

关键词：流体动力微型泵轴承湍流数值模拟测试验证出口直径电机转子模拟预测

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Characterization of meso-scale mechanical properties of Longmaxi shale using grid microindentation experiments

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Journal of Rock Mechanics and Geotechnical engineering 2021年第3期13卷 555-567页

作者： Jianting Du Andrew J.Whittle Liming Hu Thibaut Divoux Jay N.Meegoda State Key Laboratory of Hydro-Science and engineering Tsinghua UniversityBeijing100084China Department of Civil and Environmental engineering Massachusetts Institute of TechnologyCambridgeMA02139USA MultiScale Material Science for Energy and Environment UMI 3466CNRS-MITCambridgeMA02139USA Univ Lyon Ens de LyonUniv Claude BernardCNRSLaboratoire de PhysiqueLyonF-69342France Department of Civil and Environmental engineering New Jersey Institute of TechnologyNewarkNJ07102USA

Mechanical properties,such as the hardness H,Young’s modulus E,creep modulus C,and fracture toughness Kc,are essential parameters in the design of hydraulic fracturing systems for prospective shale gas *** this study,a practical methodology is presented for obtaining these properties through microindentation experiments combined with quantitative observations of the mineralogical phases using X-ray diffraction(XRD),scanning electron microscopy(SEM)with backscattered electron(BSE)imaging,and energy-dispersive X-ray spectroscopy(EDS)*** apply this method in the case of three types of Longmaxi shales with different mineralogies(***-,clay-,and quartz-rich,respectively),which allows us to determine the characteristic indentation depth,hc?8e10 mm,beyond which the mechanical response of the carbonate-rich shale is homogeneous and independent of its complex heterogeneous ***,exploiting the results of a large number of indentation tests,we demonstrate that the indentation modulus M of the shale increases as a power-law of hardness H,and its creep modulus C increases linearly with *** also compute the fracture toughness Kc from the indentation data by assuming a perfectly plastic behavior of the *** results are in good agreement with independent measurements of Kc determined by microscratch ***,further tests on quartz-and clay-rich samples of the Longmaxi shale suggest further variations in the samples’mechanical properties depending on their burial conditions and the mechanical properties of their dominant mineral phases.

关键词： Grid microindentation Mineral identification Hardness Modulus Creep Fracture toughness

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Modelling sediment transport processes in macro-tidal estuary

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Science China(Technological Sciences) 2009年第11期52卷 3368-3375页

作者： Rauen William B. Hydro-environmental Research Centre School of Engineering Cardiff University Parade Cardiff CF24 3AA UK

This paper outlines a numerical modeling study to predict the sediment transport processes in a macro-tidal estuary, namely the Mersey Estuary, UK. An integrated numerical model study is conducted to investigate the interaction between the hydrodynamic, morphological and sediment transport processes occurring in the estuary. The numerical model widely used in environmental sediment transport studies worldwide, namely ECOMSED is used to simulate flow and sediment transport in estuary. A wetting and drying scheme is proposed and applied to the model, which defines "dry" cells as regions with a thin film of fluid O (cm). The primitive equations are solved in the thin film as well as in other regular wet cells. A model for the bed load transport is included in the code to account for the dynamics of the mobile bed boundary. The bed evolution due to bed load transport which is calculated according to van Rijn (1984a) is obtained by solving the sediment mass-balance equation. An estuary-related laboratory flume experiment is used to verify the model. Six sets of field measured hydrodynamic data are used to verify the corresponding predictions of the model, with the model-predicted water elevations and salinity levels generally agreeing well with the field measurements. The numerical model results show that in the Mersey Estuary both the tidal level and river discharge affect significantly the sediment transport. Reasonable agreement between the model results and field data has been obtained, indicating that the model can be used as computer-based tool for the environment management of estuarine system.

关键词： hydraulic modelling sediment transport estuary ECOMSED flooding and drying

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Slope Debris Flows in the Wenchuan Earthquake Area

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Journal of Mountain Science 2010年第3期7卷 226-233页

作者： LI Yanfu WANG Zhaoyin SHI Wenjing WANG Xuzhao State Key Laboratory of Hydroscienee and engineering Tsinghua University Beijing 100084 China Beijing Institute of Geology for Mineral Resources Beijing 100012 China

Avalanches and landslides,induced by the Wenchuan Earthquake on May 12,2008,resulted in a lot of disaggregated,solid material on slopes that could be readily mobilized as source material for debris *** triggered numerous slope debris flows with great damage to highways and rivers over the subsequent two *** debris flows(as opposed to channelized debris flows) are defined as phenomena in which high-concentration mixtures of debris and water flow down slopes for short distances to highways and river *** on field investigations and measurements of 19 slope debris flows,their main characteristics and potential mitigation strategies were *** rainfall intensity is the main triggering *** rainfall intensities for simultaneous occurrence of single,several and numerous slope debris flow events were 20 mm/day,30mm/day,and 90 mm/day,*** investigations also revealed that slope debris flows consist of high concentrations of cobbles,boulders and *** are two-phase debris *** liquid phase plays the role of lubrication instead of transporting *** particles collide with each other and consume a lot of *** velocities of slope debris flows are very low,and their transport distances are only several tens of *** debris flows may be controlled by construction of drainage systems and by reforestation.

关键词：坡面泥石流地震区汶川固体材料高速公路中高浓度降雨强度山体滑坡

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Frictional contact algorithm study on the numerical simulation of large deformations in deep soft rock tunnels

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矿业科学技术：英文版 2010年第4期20卷 524-529页

作者： GUO Hongyun CHEN Xin HE Manchao XI Shouzhong TANG Juzhen School of Mechanics & Civil engineering China University of Mining & Technology Beijing 100083 China State Key Laboratory for GeoMechanics and Deep Underground engineering Beijing 100083 China Beijng HPDI Geotechnical Investigation & Surving Co. Ltd. Beijing 100088 China Beijing FEGEN Software Co. Ltd. Beijing 100098 China

There exist three types of nonlinear problems in large deformation processes of deep softrock engineering, i.e., nonlinearity caused by material, geometrical and contact boundary. In this paper, the numerical method to tackle the nonlinear contact and large deformation problem in A Software on Large Deformation Analysis for Soft Rock engineering at Great Depth was presented. In the software, based on Lagrange multiplier method and Coulomb friction law, kinematic constraints on contact boundaries were introduced in functional function, and the finite element equations was established for two incremental large deformation analyses models, polar decomposition model and additive decomposition model. For every incremental loading step, by searching for the contact points in the potential contact interfaces (the excavation boundaries), the Lagrange multipliers, i.e., contact forces are calculated iteratively by Gauss-Seidel method, and justified through satisfy the inequalities of static constraint on contact boundaries. With the software, large deformation and frictional contact of a transport roadway were analyzed numerically by the two models. The numerical examples demonstrated the efficiency of the method used in the software.

关键词：大变形问题摩擦接触数值模拟软岩巷道支护拉格朗日乘数法非线性问题深部变形分析模型

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Experimental Study on the Dam-Break Hydrographs at the Gate Location

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Journal of Ocean University of China 2017年第4期16卷 697-702页

作者： LIU Hui LIU Haijiang GUO Liheng LU Senxun Ocean College Zhejiang University Hangzhou 310058 P R. China College of Civil engineering and Architecture Zhejiang University Hangzhou 310058 P R. China

When studying the dam-break flow phenomenon,the basic hydrodynamic features of the dam-break flow at the gate location should be verified *** this study,laboratory experiments were performed in a rectangular and horizontal flume with the same initial water head setting on the dry and wet downstream bed *** surface elevation was extracted through image analysis and validated by comparing with the data measured using a wave *** variation of the water surface elevation at the gate location,quantified in terms of high-speed video recorded images,can be divided into three stages,the sharp decreasing stage,the relatively steady stage,and the gradually decreasing *** of several classic analytical solutions of the dam-break problem at the gate location was validated using present experimental ***'s solution is effective for the dry bed condition while Stoker's solution could be applied to the wet bed case,and both are only applicable during the steady ***' solution reproduces the gate-site hydrographs well during both the relatively steady and the gradually decreasing stages,especially for the condition under which the down-upstream water depth ratio is smaller than 0.138.

关键词：溃坝水流实验室实验浇口位置对比验证图像分析水动力特征初始水头下游河床

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Dynamic instability of a pump-turbine in load rejection transient process

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Science China(Technological Sciences) 2018年第11期61卷 1765-1775页

作者： FU XiaoLong LI DeYou WANG HongJie ZHANG GuangHui Li ZhengGui WEI XianZhu School of Energy Science and engineering Harbin Institute of Technology Key Laboratory of Fluid and Power Machinery (Xihua University) Ministry of Education Sichuan State Key Laboratory of Hydro-Power Equipment Harbin Institute of Large Electrical Machinery

Load rejection is one of the most crucial transient processes in pump-turbines. However, only a few achievements on the internal flow mechanism of pump-turbines in load rejection processes have been presented. In this study, firstly, the load rejection process in a pump-turbine was simulated with a three-dimensional unsteady turbulent numerical method using the technology of dynamic mesh and the user-defined functions in the FLUENT software. The rotational speed predicted through numerical simulation agrees well with experimental data. Secondly, based on numerical simulations, a dynamic instability in the load rejection process was found and presented that the pressure and performance characteristics, including hydraulic torque on the runner and the discharge, fluctuate in the overall trend. Meanwhile, all the performance characteristics and the pressure fluctuate sharply near the operating condition points, where hydraulic torque on the runner is equal to zero or reverse flow is maximum at reverse pump conditions. Finally, the time-frequency features and formation mechanism of the dynamic instability were analyzed emphatically. The analysis of the internal flow in the pump-turbine reveals that dynamic instability in the load rejection process are mainly caused by the vortex flow in the tandem cascades regions. Furthermore, the possible methods to improve the dynamic instability in the load rejection process were recommended.

关键词： pump-turbine load rejection process dynamic instability numerical simulation

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SEDIMENTATION AND EROSION STUDIES

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International Journal of Sediment Research 2005年第1期20卷 4-4页

作者： Chih Ted YANG Colorado State UniversityUSA Director of hydroscience and Training Center Endowed Borland Professor of Water Resources Prof. Vice President of World Association for Sedimentation and Erosion Research (WASER)

The river systems observed today is the cumulative result of surface, rill, and gully erosion, and sediment transport, scour, and deposition. The divisions of approach between these two related areas are man-made, and are not based on sound science. Most of the erosion studies are done by geologists and agricultural engineers who are concerned of the surface, rill, and gully erosion and the loss of agricultural land productivity. Hydraulic engineers are more interested in the study of sediment transport, scour, and deposition, and their impacts on river engineering and hydraulic structures in rivers and reservoirs. Erosion studies are often based on empirical relationships or field data to determinate the annual sediment yield from a watershed. On the other hand, hydraulic engineers focus their attention on solving equations based on assumed initial and boundary conditions with a time scale of days, hours, or seconds. Both approaches have their complementary strengths and weaknesses. It is important to provide a forum for specialists in both areas to communicate, exchange ideas, and learn from each other.

关键词： SEDIMENTATION AND EROSION STUDIES high

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Stochastic evolution of hydraulic geometry relations in the lower Yellow River of China under environmental uncertainties

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International Journal of Sediment Research 2020年第4期35卷 328-346页

作者： Xiaolong Song Deyu Zhong Guangqian Wang Xiaonan Li State Key Laboratory of Hydro-science and engineering Tsinghua University State Key Laboratory of Hydraulic Engintering Simulation and Safety Tianjin University Changjiang Survey PlanningDesign and Research Co.Ltd

Hydraulic geometry relations comprise a classic way to understand characteristics of a ***,environmental changes pose large uncertainties for the reliability of such *** the current study,on the basis of the ordinary differential equations(ODEs) formed through linear treatment of the deterministic power-law hydraulic geometry relations,a set of stochastic differential equations(SDEs)driven by Fractional white noise and Poisson noise are developed to simulate the historical dynamic probability distributions of typical hydraulic geometry variables such as slope,width,depth,and velocity with bankfull discharge variation over time in the lower Yellow River of *** group of possible stochastic average behaviors within the next 50 years are calculated under three different design incoming water-sediment conditions(including 300,600,and 800 million t of annual average sediment discharge).In each part of the lower reaches,after estimation of the SDE parameters using a nonparametric maximum likelihood estimation(MLE) method,the model is carefully examined using Monte Carlo simulation as compared with the deterministic control *** results of this comparison reveal the potential responses of hydraulic geometry characteristics to environmental disturbances,and the average trends mainly agree with the *** among the three different prediction results reveal the stochastic average solution generally is greater than the deterministic *** results also confirm the severe negative impacts that result from the condition of 300 million t of incoming sediment,thus,pointing out the need to raise the level of river evolution alert for the lower Yellow River of China in the ***,with the help of the stochastic computation,the stream power and hydraulic width/depth ratio could be representative of an effective systematic measure for river *** proposed stochastic approach is not only important to development in t

关键词： Hydraulic geometry relations Environmental uncertainties Stochastic differential equation Lower Yellow River River system

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