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THREE-DIMENSIONAL SIMULATION OF MEANDERING RIVER BASED ON 3-D RNG k-ε TURBULENCE MODEL

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Journal of Hydrodynamics 2008年第4期20卷 448-455页

作者： ZHANG Ming-liang SHEN Yong-ming State Key Laboratory of Coastal and offshore engineering Dalian University of Technology Dalian 116024China department of Civil and Structural engineering The Hong Kong Polytechnic University Hong Kong China

A 3-D numerical model for calculating flow in non-curvilinear coordinates was established in this article. The flow was simulated by solving the full Reynolds-averaged Navier-Stokes equations with the RNG κ-ε turbulence model. In the horizontal x-y-plane, a boundary-fitted curvilinear co-ordinate system was adopted, while in the vertical direction, a σ co-ordinate transformation was used to represent the free surface and bed topography. The water level was determined by solving the 2-D Poisson equation derived from 2-D depth averaged momentum equations. The finite-volume method was used to discretize the equations and the SIMPLEC algorithm was applied to acquire the coupling of velocity and pressure. This model was applied to simulate the meandering channels and natural rivers, and the water levels and the velocities for all sections were given. By contrasting and analyzing, the agreement with measurements is generally good. The feasibility studies of simulating flow of the natural fiver have been conducted to demonstrate its applicability to hydraulic engineering research.

关键词： non-orthogonal curvilinear coordinates RNG κ-ε turbulence model 2-D Poisson equation SIMPLEC algorithm depth averaged equation

Optimization of process parameters of the activated tungsten inert gas welding for aspect ratio of UNS S32205 duplex stainless steel welds

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Defence Technology（防务技术） 2014年第3期10卷 251-260页

作者： G.MAGUDEESWARAN Sreehari R.NAIR L.SUNDAR N.HARIKANNAN department of Mechanical engineering PSNA College of Engineering and Technology Ador welding Limited Melakottaiyur

The activated TIG(ATIG) welding process mainly focuses on increasing the depth of penetration and the reduction in the width of weld bead has not been paid much *** shape of a weld in terms of its width-to-depth ratio known as aspect ratio has a marked influence on its solidification cracking *** major influencing ATIG welding parameters,such as electrode gap,travel speed,current and voltage,that aid in controlling the aspect ratio of DSS joints,must be optimized to obtain desirable aspect ratio for DSS *** in this study,the above parameters of ATIG welding for aspect ratio of ASTM/UNS S32205 DSS welds are optimized by using Taguchi orthogonal array(OA)experimental design and other statistical tools such as Analysis of Variance(ANOVA) and Pooled ANOVA *** optimum process parameters are found to be 1 mm electrode gap,130 mm/min travel speed,140 A current and 12 V *** aspect ratio and the ferrite content for the DSS joints fabricated using the optimized ATIG parameters are found to be well within the acceptable range and there is no macroscopically evident solidification cracking.

关键词： Duplex stainless steel ATIG welding Aspect ratio Taguchi design Ferrite number Solidification cracking

Improving Fatigue Properties of 316L Stainless Steel Welded Joints by Surface Spinning Strengthening

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Acta Metallurgica Sinica(English Letters) 2024年第5期37卷 840-854页

作者： Dongqiqiong Wang Qiang Wang Xiaowu Li Zhefeng Zhang department of Materials Physics and Chemistry School of Materials Science and Engineeringand Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education)Northeastern UniversityShenyang 110819China Shi-Changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China College of Light Industry Liaoning UniversityShenyang 110036China

The surface spinning strengthening(3S)mechanism and fatigue life extension mechanism of 316L stainless steel welded joint were systematically elucidated by microstructural analyses and mechanical *** indicate that surface gradient hardening layer of approximately 1 mm is formed in the base material through grain fragmentation and deformation twin strengthening,as well as in the welding zone composed of deformedδ-phases and *** fatigue strength of welded joint after 3S significantly rises by 32%(from 190 to 250 MPa),which is attributed to the effective elimination of surface geometric defects,discrete refinement ofδ-Fe phases and the appropriate improvement in the surface strength,collectively mitigating strain localization and surface fatigue damage within the gradient strengthening *** redistributed fineδ-Fe phases benefited by strong stress transfer of 3S reduce the risk of surface weak phase cracking,causing the fatigue fracture to transition from microstructure defects to crystal defects dominated by slip,further suppressing the initiation and early propagation of fatigue cracks.

关键词： 316L stainless steel Welded joint Surface spinning strengthening Nanotwin Fatigue life

Full time-domain nonlinear coupled dynamic analysis of a truss spar and its mooring/riser system in irregular wave

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Science China(Physics,Mechanics & Astronomy) 2014年第1期57卷 152-165页

作者： YANG MinDong TENG Bin XIAO LongFei NING DeZhi SHI ZhongMin QU Yan Guangdong Electric Power Design Institute China Energy Engineering Group Co. Ltd. department of Ocean engineering Ocean University of China State Key Laboratory of Coastal and offshore engineering Dalian University of Technology State Key Laboratory of Ocean engineering Shanghai Jiao Tong University Technology Research department China National Offshore Oil Corporation

A new full time-domain nonlinear coupled method has been established and then applied to predict the responses of a Truss Spar in irregular wave. For the coupled analysis, a second-order time-domain approach is developed to calculate the wave forces, and a finite element model based on rod theory is established in three dimensions in a global coordinate system. In nu- merical implementation, the higher-order boundary element method （HOBEM） is employed to solve the velocity potential, and the 4th-order Adams-Bashforth-Moultn scheme is used to update the second-order wave surface. In deriving convergent solu- tions, the hull displacements and mooring tensions are kept consistent at the fairlead and the motion equations of platform and mooring-lines/risers are solved simultaneously using Newmark-fl integration scheme including Newton-Raphson iteration. Both the coupled quasi-static analysis and the coupled dynamic analysis are performed. The numerical simulation results are also compared with the model test results, and they coincide very well as a whole. The slow-drift responses can be clearly ob- served in the time histories of displacements and mooring tensions. Some important characteristics of the coupled responses are concluded.

关键词： coupled method full time-domain second-order truss spar rod theory irregular wave

Hydraulic Modeling of A Curtain-Walled Dissipater by the Coupling of RANS and Boussinesq Equations

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China Ocean engineering 2002年第2期17卷 201-210页

作者： QI Peng(齐鹏) WANG Yongxue(王永学) department of Hydraulic engineering Tsinghua University Beijing 100084 China State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology Dalian 116024 China

A hybrid numerical method for the hydraulic modeling of a curtain-walled dissipater of reflected waves from breakwaters is presented. In this method, a zonal approach that combines a nonlinear weakly dispersive wave (Boussinesq-type equation) method and a Reynolds-Averaged Navier-Stokes (RANS) method is used. The Boussinesq-type equation is solved in the far field to describe wave transformation in shallow water. The RANS method is used in die near field to resolve the turbulent boundary layer and vortex flows around the structure. Suitable matching conditions are enforced at the interface between the viscous and the Boussinesq region. The Coupled RANS and Boussinesq method successfully resolves the vortex characteristics of flow in the vicinity of the structure, while unexpected phenomena like wave re-reflection are effectively controlled by lengthening the Boussinesq region. Extensive results on hydraulic performance of a curtain-walled dissipater and the mechanism of dissipation of reflected waves are presented, providing a reference for minimization of die breadth of the water chamber and for determination of the submerged depth of the curtain wall.

关键词： numerical simulation hybrid numerical method viscous flow curtain-walled dissipater

Target-oriented Q-compensated reverse-time migration by using optimized pure-mode wave equation in anisotropic media

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Petroleum Science 2023年第2期20卷 866-878页

作者： Shi-Gang Xu Qian-Zong Bao Zhi-Ming Ren Chang'an University School of Geological Engineering and GeomaticsDepartment of GeophysicsXi'anShaanxi710064China National engineering Research Center of offshore Oil and Gas Exploration Beijing100028China

Research on seismic anisotropy and attenuation plays a significant role in exploration geophysics. To enhance the imaging quality for complicated structures, we develop several effective improvements for anisotropic attenuation effects in reverse-time migration (Q-RTM) on surface and vertical seismic profiling (VSP) acquisition geometries. First, to suppress pseudo-shear wave artifact and numerical instability of the commonly used anisotropic pseudo-acoustic wave equations, an optimized pure P-wave dispersion relation is derived and the corresponding pure-mode wave equation is solved by combining the finite-difference and Possion methods. Second, a simplified anisotropic pure-mode visco-acoustic wave equation (PVAWE) based on standard linear solid model is established. Third, a time-dispersion correlation strategy is applied to improve the modeling accuracy. Fourth, we extend a target-oriented scheme to anisotropic attenuated modeling and imaging. Instead of the conventional wavefield modeling and RTM, the proposed approach can extract available wavefield information near the target regions and produce high imaging resolution for target structures. Last, both anisotropic surface and VSP Q-RTMs are executed by combining optimized PVAWE, time-dispersion correlation and target-oriented algorithm. Modeling examples demonstrate the advantages of our schemes. Moreover, our modified Q-compensated imaging workflow can be regarded as a supplement to the classical anisotropic RTM.

关键词： Anisotropy Attenuation Reverse-time migration Wave equation Optimized algorithm Target-oriented

High temperature behaviors of high velocity arc sprayed Fe-Al/Cr_3C_2 composite coatings

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Journal of University of Science and Technology Beijing 2005年第4期12卷 340-346页

作者： Weipu Xu Binshi Xu Wei Zhang Yixiong Wu welding Institute of Materials Science and engineering department Shanghai Jiaotong University Shanghai 200030 China National Key Laboratory for Remanufacturing Beijing 100072 China

Fe-Al/Cr3C2 composite coatings were manufactured using high velocity arc spraying （HVAS） technology. The high temperature erosion, wear and corrosion resistance of the coatings were investigated. The coating properties such as bonding strength, porosity, hardness as well as microstructures were characterized. The results show that the coatings have relatively high heat tremble bond strength, hardness, and typical layer-shaped coatings＇ microstructures. With the rise of temperature, the coating erosion resistance increases too; the impingement angel does effects on erosion properties, and the erosion mechanism changes from ductile to brittle behaviors at 450℃. The coatings have good room temperature wear resistance and relatively good high temperature resistance. The wear mechanism of the coatings is peeling wear behavior. The coatings have excellent high temperature corrosion resistance because of the produce of oxides during corrosion.

关键词： Fe-Al/Cr3C2 coating erosion wear corrosion

METHODS FOR IDENTIFYING SUB-REGIONAL MATERIAL PARAMETERS OF CONCRETE DAMS USING MODAL DATA

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Acta Mechanica Solida Sinica 2003年第1期16卷 88-94页

作者： Feng Xin Zhou Jing Fan Yingfang department of Building engineering Tongji UniversityShanghai 200092China State Key Lab of offshore■Coastal engineering Department of Civil EngineeringDalian University of TechnologyDalian 116024China

Methods for identifying sub-regional material parameters of concrete damsusing incomplete rnodal data are presented. With the measurements of the first frequency andincomplete mode shape, identification methods were built by both the output error approach and theminimum deviation approach. The minimum deviation approach was introduced as physical constraints tothe output error approach, allowing the output error-minimum deviation coupled approach to bedeveloped. The simulated annealing-simplex shape algorithm was applied to solve the identificationmodels. Numerical simulations were carried out with noisy incomplete measurements to illustrate therobustness of the methods.

关键词： concrete dam parameter identification output error approach minimumdeviation approach simulated annealing-simplex shape algorithm

A two-step approach to investigate the effect of rating curve uncertainty in the Elbe decision support system

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Journal of Zhejiang University-Science A(Applied Physics & engineering) 2008年第9期9卷 1229-1238页

作者： Yue-ping XU Harriette HOLZHAUER Martijn J. BOOIJ Hong-yue SUN Institute of Hydrology and Water Resources Department of Civil Engineering Zhejiang University Hangzhou 310027 China Water engineering and Management Faculty of Engineering Technology University of Twente 7500 AE Ensehede the Netherlands Institute of Harbor Coast and Offshore Engineering Department of Civil Engineering Zhejiang University Hangzhou 310027 China

For river basin management, the reliability of the rating curves mainly depends on the accuracy and time period of the observed discharge and water level data. In the Elbe decision support system (DSS), the rating curves are combined with the HEC-6 model to investigate the effects of river engineering measures on the Elbe River system. In such situations, the uncertainty originating from the HEC-6 model is of significant importance for the reliability of the rating curves and the corresponding DSS results. This paper proposes a two-step approach to analyze the uncertainty in the rating curves and propagate it into the Elbe DSS: analytic method and Latin Hypercube simulation. Via this approach the uncertainty and sensitivity of model outputs to input parameters are successfully investigated. The results show that the proposed approach is very efficient in investigating the effect of uncertainty and can play an important role in improving decision-making under uncertainty.

关键词： Elbe decision support system (DSS) Two-step approach Uncertainty HEC-6 model