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numerical modeling of space-time wave extremes using WAVEWATCH III

OCEAN DYNAMICS 2017年第3-4期67卷 535-549页

作者： Barbariol, Francesco Alves, Jose-Henrique G. M. Benetazzo, Alvise Bergamasco, Filippo Bertotti, Luciana Carniel, Sandro Cavaleri, Luigi Chao, Yung Y. Chawla, Arun Ricchi, Antonio Sclavo, Mauro Tolman, Hendrik ISMAR CNR Venice Italy Syst Res Grp Inc Environm Modeling Ctr NOAA NCEPEnvironm Modeling Ctr College Pk MD USA NOAA Environm Modeling Ctr NCEP Marine Modeling & Anal Branch College Pk MD USA Ca Foscari Univ Venice Venice Italy Univ Politecn Marche Ancona Italy

A novel implementation of parameters estimating the space-time wave extremes within the spectral wave modelWAVEWATCH III (WW3) is presented. The new output parameters, available in WW3 version 5.16, rely on the theoretical model of Fedele (J Phys Oceanogr 42( 9): 1601-1615, 2012) extended by Benetazzo et al. (J Phys Oceanogr 45( 9): 2261-2275, 2015) to estimate the maximum secondorder nonlinear crest height over a given space-time region. In order to assess the wave height associated to the maximum crest height and the maximum wave height (generally different in a broad-band stormy sea state), the linear quasi-determinism theory of Boccotti (2000) is considered. The new WW3 implementation is tested by simulating sea states and space-time extremes over the Mediterranean Sea ( forced by the wind fields produced by the COSMO-ME atmospheric model). Model simulations are compared to space-time wave maxima observed on March 10th, 2014, in the northern Adriatic Sea (Italy), by a stereo camera system installed on-board the "Acqua Alta" oceanographic tower. Results show that modeled space-time extremes are in general agreement with observations. Differences are mostly ascribed to the accuracy of the wind forcing and, to a lesser extent, to the approximations introduced in the space-time extremes parameterizations. Model estimates are expected to be even more accurate over areas larger than the mean wavelength (for instance, the model grid size).

关键词： Space-time wave extremes WAVEWATCH III Ocean waves Stereo vision numerical modeling

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numerical modeling of ceria-based SOFCs with bi-layer electrolyte free from internal short circuit: Comparison of two cell configurations

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ELECTROCHIMICA ACTA 2017年 248卷 356-367页

作者： Wang, Xinxin Zhang, Teng Kang, Jianhong Zhao, Ling Guo, Litong Feng, Peizhong Zhou, Fubao Ling, Yihan China Univ Min & Technol Key Lab Gas & Fire Control Coal Mines Minist Educ Xuzhou 221116 Peoples R China China Univ Min & Technol Sch Safety Engn Xuzhou 221116 Peoples R China China Univ Min & Technol Sch Mat Sci & Engn Xuzhou 221116 Peoples R China China Univ Geosci Dept Mat Sci & Chem Wuhan 430074 Hubei Peoples R China

A numerical model for ceria-based solid oxide fuel cells (SOFCs) with bi-layer electrolyte is proposed to evaluate the internal short circuit by the comparison of two cell configurations: the electronic barrier electrolyte adjacent to cathode and anode, respectively. In this model, the activation polarization of the electrode reaction and the charge transport of the electrolyte with both n/p-type electronic and oxygen ion conductivity are considered. The activation polarization and the charge transport are described by the Butler-Volmer equation and the Nernst-Planck equation, respectively. Parametric simulations are performed to compare the two bi-layer electrolyte configurations in terms of the open circuit voltage, I-V relationship, leakage current density, power density at 0.7 V, oxygen partial pressure distribution and electrochemical efficiency as functions of the temperature and thickness ratio of the electronic barrier electrolyte. From our modeling results, the cell configuration of which the barrier electrolyte is adjacent to cathode has significant p-type leakage current, leading to the lower open circuit voltages and electrochemical efficiency than the other one. The oxygen partial pressure distribution under the open circuit displays the "S" type in the barrier layer, which is related to the change of the n/p-type conductivity of the barrier layer. Besides, the activation polarization greatly influences the open circuit voltage and the oxygen partial pressure distribution between boundaries of electrolytes under open circuit. It is also found that the thickness ratio of the electronic barrier electrolyte can be optimized to maximize the electrochemical performance by balancing the open circuit voltage and ohmic polarization loss. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： numerical modeling Ceria-based solid oxide fuel cell Bi-layer electrolyte Electronic barrier layer

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numerical modeling of behavior of railway ballasted structure with geocell confinement

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GEOTEXTILES AND GEOMEMBRANES 2013年第Feb.期36卷 33-43页

作者： Leshchinsky, Ben Ling, Hoe I. Oregon State Univ Dept Forest Engn Resources & Management Corvallis OR 97331 USA Columbia Univ Dept Civil Engn & Engn Mech New York NY 10027 USA

Railroad foundations are geotechnical structures that are highly dependent on quality ballast to dampen impact loading and railway vibration, facilitate easy construction, distribute stresses more evenly, reduce long-term settlements and provide a competent base under low confining pressures. However, there are various instances where the use of ballast alone may not be completely adequate or could be prohibitively expensive, i.e. costly transport of select materials, weak subgrade, etc. One possible method of managing these issues is the use of geosynthetics, primarily reinforcements that utilize a confining mechanism to enhance the strength of a soil by utilizing its own internal friction: a mechanism where geocell is applicable. Based on prior large-scale laboratory tests of ballast embankments with geocell confinement and relevant numerical modeling, an acceptable material model was validated for a parametric study using finite element analysis. The purpose of the parametric study is to investigate the effects of geocell confinement on ballasted embankments when encountering a soft subgrade, weaker ballast, or varying reinforcement stiffnesses. This analysis suggests that based on numerical modeling, geocell confinement can have a significant benefit when used on a wide range of subgrade stiffnesses, when using weaker ballast and that mechanically, most polymeric materials commonly used for geosynthetic reinforcements are adequate. The composite effect of the confined ballast selected as infill also demonstrates a "mattressing" effect, distributing stresses more uniformly to the subgrade, which can provide higher bearing capacities and possibly less settlement, all while preventing significant lateral spreading. In certain situations, the benefits provided by behavior of the geocell-ballast composite may be economical by allowing for use of weaker/inferior ballast, less embankment maintenance upon problem soils, improved bearing capacity and reduced foundation s

关键词： Railroad Ballast Geocell Confinement numerical modeling Finite element

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numerical modeling of stress and strain associated with the bending of an oil pipeline by a migrating pingo in the permafrost region of the northern Tibetan Plateau

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ENGINEERING GEOLOGY 2008年第1-2期96卷 62-77页

作者： Wu, Zhenhan Barosh, Patrick J. Wang, Lianjie Hu, Daogong Wang, Wei PJ Barosh & Assoc Bristol RI 02809 USA Chinese Aca3demy Geol Sci Inst Geomech Beijing 100081 Peoples R China

Small seasonal pingos formed in Quaternary deposits along active fault zones in permafrost of the northern Tibetan Plateau exert destructive forces to oil pipelines, bridges, culverts and other engineering facilities along the Golmud-Lhasa railway and highway. The pingos are particularly hazardous as they change position, or migrate, nearly every year. Three-dimensional finite element modeling reveals the enormous force from exerted by a pingo at the 86th station of the highway. A good representation of the stress and strain fields resulting from an expansion of a pingo and bending of an oil pipeline at the station are calculated after due consideration of the interaction between permafrost, pingo and pipeline. This followed establishing an engineering-geologic model from the field data and determining the mechanical properties of the media from field and laboratory tests. The maximum, intermediate and the minimal principal compressive stresses are calculated as well as those for the plastic strain. Concentrations of principal stress and plastic strain occur beneath the pipeline bend and both the principal compressive stress and resulting plastic strain become very small away from the pingo. Also, the bottom of the pingo is dominated by minimal values of principal stress and strain and the potential bending of a buried pipe caused by an expansion of a pingo is indicated to decrease as depth of burial increases. The pingo growth at the 86th station resulted in the bending upward of a 20m section of a buried oil pipeline, but it did not break and spill oil. Analysis of the pipe within the bend found the maximum, intermediate, and minimal principal compressive stress ranges that leads to plastic strain within the bent pipe. Compressive stress and plastic strain concentrations form in the inner sides of inflexions in the pipe bend, and tensional stress and plastic strain concentrations form in their outer sides where stress exceeds the yield limit of the pipe, but many

关键词： migrating pingo numerical modeling stress plastic strain permafrost Tibetan Plateau hazard assessment Golmud-Lhasa Railway

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numerical modeling of hypervelocity impacts

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INTERNATIONAL JOURNAL OF IMPACT ENGINEERING 2006年第1-12期33卷 244-253页

作者： Fortov, V. E. Kim, V. V. Lomonosov, I. V. Matveichev, A. V. Ostrik, A. V. Russian Acad Sci Inst Problems Chem Phys Chernogolovka 142432 Russia

This research presents a new "finite-size particle in cell" method developed for numerical modeling of processes at high energy density. It uses the Lagrangian-Eulerian representation of media which allows one to match contact and free surfaces and to calculate flows with strong deformations. Efficient models of thermodynamic properties, elastic-plastic deformation and fragmentation have been employed in the gas dynamic code adapted for parallel computations. 3D and 2D numerical modeling of plate penetration by impactors of different geometry has been done in a wide range of velocities. The influence of used materials properties models on numerical results has been investigated. (C) 2006 Elsevier Ltd. All rights reserved.

关键词： hypervelocity impact numerical modeling

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numerical modeling of seawater intrusion in Zhoushuizi district of Dalian City in northern China

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ENVIRONMENTAL EARTH SCIENCES 2016年第9期75卷 1-18页

作者： Zhao, Jie Lin, Jin Wu, Jianfeng Yang, Yun Wu, Jichun Nanjing Univ Sch Earth Sci & Engn Minist Educ Dept HydrosciKey Lab Surficial Geochem Nanjing 210023 Jiangsu Peoples R China Nanjing Hydraul Res Inst Nanjing 210029 Jiangsu Peoples R China Hohai Univ Sch Earth Sci & Engn Nanjing 210008 Jiangsu Peoples R China

Since 1980s, seawater intrusion in coastal aquifers caused by groundwater over-abstraction has led to extensive deterioration in groundwater quality and quantity and has been fazing local residents in Zhoushuizi district of the metropolitan Dalian City in northern China. In this study, a three-dimensional (3D) density-dependent numerical model was constructed to simulate the seawater intrusion process in heterogeneous coastal aquifers in Zhoushuizi district of the metropolitan Dalian City. Considering that the groundwater flow in karst aquifers in northern China is relatively uniform, approximately following Darcy's law, the fracture-karst aquifer in Zhoushuizi district of Dalian City was simplified as an equivalent porous medium. To further identify the hydrogeological parameters of the aquifers in the study area, the model was calibrated and validated using the observation heads and concentrations. Based on the current groundwater abstraction conditions of the study area, the calibrated and validated model was then applied to predict the dynamics and trend of seawater intrusion for the following 30 years from 2010 to 2040 under different rainfall scenarios. The overall extent of seawater intrusion in the future would be even more severe under different prediction scenarios. This 3D seawater intrusion model provides the theoretical basis for implementing a reasonable allocation of groundwater resource, which may significantly affect the sustainability of water resources.

关键词： numerical modeling Coastal aquifers Seawater intrusion Tidal effect Northern China

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numerical modeling of the thermomechanical behavior of steels with allowance for the propagation of Luders bands

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JOURNAL OF APPLIED MECHANICS AND TECHNICAL PHYSICS 2007年第5期48卷 743-750页

作者： Balokhonov, R. R. Romanova, V. A. Russian Acad Sci Inst Strength Phys & Mat Sci Siberian Div Tomsk 634021 Russia Tomsk VV Kuibyshev State Univ Tomsk 634050 Russia

A thermomechanical model based on physical representations of the motion of dislocation continuum and a model for the initiation and propagation of plastic shear are proposed to describe slow flows of the type of Luders bands. Two-dimensional calculations of Luders band propagation are performed for HSLA-65 steel samples under compression at various strain rates and temperatures. The calculation results are in good agreement with experimental data.

关键词： numerical modeling Luders bands relaxation constitutive equation rate and temperature sensitivity

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numerical modeling of observed effective flow behavior in unsaturated heterogeneous sands

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WATER RESOURCES RESEARCH 1999年第1期35卷 29-42页

作者： Wildenschild, D Jensen, KH Tech Univ Denmark Dept Hydrodynam & Water Resources DK-2800 Lyngby Denmark

The concept of effective parameters has been introduced in recent years to represent the spatial variability of natural soils in numerical simulation models. In the present study, effective hydraulic properties of unsaturated flow were investigated for the case of a two-dimensional heterogeneous laboratory tank. Hydraulic parameter estimates obtained from simple statistical averages, inverse procedures, and a stochastic theory were compared to effective retention and hydraulic conductivity characteristics measured for the whole tank at steady state. The applicability of the effective parameter estimates was investigated by comparing transient flow events monitored in the laboratory tank with simulated results based on those estimates. Capillary suction measurements were simulated reasonably well using several straight forward arithmetic and geometric statistical averaging approaches, whereas most averaging approaches simulated too slow a response in the outflow rate. An alternative approach involving a combination of arithmetic and geometric averaging of the measured values more closely simulated the observed relatively fast changes in outflow rate. Generally, the simulations based on the measurements of effective properties performed quite well, indicating that the fundamental concept of effective parameters may be valid for this type of heterogeneous soil system.

关键词： .inverse hydraulic conductivity spatial variability flow rate unsaturated flow numerical modeling effective flow natural soils effective hydraulic parameter estimates averages stochastic theory transient flow Capillary suction arithmetic averaging

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numerical modeling OF WALL-INJECTED SCRAMJET EXPERIMENTS

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JOURNAL OF PROPULSION AND POWER 1993年第2期9卷 169-175页

作者： BRESCIANINI, CP MORGAN, RG University of Queensland Brisbane Queensland Australia

A wall-injected, hydrogen-fueled scramjet is modeled numerically using a parabolic Navier-Stokes computer code with a k-epsilon turbulence model and finite-rate chemistry. The numerical results are compared to experimental scramjet data taken in a shock tunnel and are found to be in reasonable agreement. At the conditions studied, the numerical results show that combustion in the scramjet is mainly mixing limited.

关键词： Scramjet Engines Shock Tunnels numerical modeling Hydrogen Fuels Turbulence Models Heat Transfer Measurements Static Pressure Logarithmic Law of the Wall Combustion Efficiency Computational Fluid Dynamics

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numerical modeling of Roller Leveler for Thick Plate Leveling

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INTERNATIONAL JOURNAL OF PRECISION ENGINEERING AND MANUFACTURING 2018年第3期19卷 425-430页

作者： Jong-Bin Lee Kang, Sung-Soo POSCO SS VINA Roll Design Team N1 StPhu My 2 Ind Zone Tan Thanh Dist 790000 BRVT Province Vietnam Jeonju Univ Dept Mech & Automot Engn 303 Cheonjam Ro Jeonju Si 55069 Jeollabuk Do South Korea

To ensure quality of the steel structures used in the shipbuilding and construction industry, the thick plate market increasingly demands for more flatness and higher residual stress. Diminishing slit camber caused by residual stress and incorrect flatness due to aging effect has recently emerged as important quality issues. In the current study, we proposed a new numerical model for a twodimensional roller leveler which calculates the curvature and moment of the material depending on the intermesh. This curvature was used to calculate the stress and strain values of the material along the thickness direction. Correction factors were also introduced to correct the location of the contact point that changes when the relationship between the intermesh and curvature was assumed as three-point bending of a concentrated load at the plate center. The result from this numerical model and that of the finite element analysis were compared to verify the effectiveness of this model.

关键词： numerical modeling Roller leveler Thick plate Residual stress Intermesh Finite element analysis

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