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Large-eddy simulation of flows past a flapping airfoil using immersed boundary method

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Science china(Physics,mechanics & Astronomy) 2010年第6期53卷 1101-1108页

作者： YANG xiaolei,HE GuoWei & ZHANG Xing The state {2. Laboratory of nonlinear mechanics,institute of mechanics,chinese academy of sciences,beijing 100190,{12. The state key Laboratory of {2. mechanics Institute of Mechanics Chinese Academy of Sciences Beijing China

The numerical simulation of flows past flapping foils at moderate Reynolds numbers presents two challenges to computational fluid dynamics: turbulent flows and moving boundaries. The direct forcing immersed boundary(IB) method has been developed to simulate laminar flows. However,its performance in simulating turbulent flows and transitional flows with moving boundaries has not been fully evaluated. In the present work,we use the IB method to simulate fully developed turbulent channel flows and transitional flows past a stationary/plunging SD7003 airfoil. To suppress the non-physical force oscillations in the plunging case,we use the smoothed discrete delta function for interpolation in the IB method. The results of the present work demonstrate that the IB method can be used to simulate turbulent flows and transitional flows with moving boundaries.

关键词： transitional flows moving boundary immersed boundary method smoothed discrete delta function

nonlinear FLUID DAMPING IN STRUCTURE-WAKE OSCILLATORS IN MODELING VORTEX-INDUCED VIBRATIONS

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Journal of Hydrodynamics 2009年第1期21卷 1-11页

作者： LIN Li-ming LING Guo-can wu Ying-xiang ZENG Xiao-hui Division of Engineering sciences Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China The state key Laboratory of {2. mechanics Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China

A nonlinear Fluid Damping （NFD） in the form of the square-velocity is applied in the response analysis of Vortex-Induced Vibrations （VIV）. Its nonlinear hydrodynamic effects on the coupled wake and structure oscillators are investigated. A comparison between the coupled systems with the linear and nonlinear fluid dampings and experiments shows that the NFD model can well describe response characteristics, such as the amplification of body displacement at lock-in and frequency lock-in, both at high and low mass ratios. Particularly, the predicted peak amplitude of the body in the Griffin plot is in good agreement with experimental data and empirical equation, indicating the significant effect of the NFD on the structure motion.

关键词： Vortex-Induced Vibration (VIV) nonlinear Fluid Damping (NFD) wake oscillator

Influence of processing temperature on microstructure and microhardness of copper subjected to high-pressure torsion

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Science china(Technological sciences) 2010年第6期53卷 1534-1539页

作者： XIE ZiLing1,2.XIE JiJia2.HONG YouShi2.& wu xiaolei2.1 College of Architecture and Civil Engineering,University of Wenzhou,Wenzhou 32.035,{2. 2.state key Laboratory of nonlinear mechanics,institute of mechanics,chinese academy of sciences,{12. 100190,{2. College of Architecture and Civil Engineering University of Wenzhou Wenzhou China state key Laboratory of {2. mechanics Institute of Mechanics Chinese Academy of Sciences Beijing China

Cu samples were subjected to high-pressure torsion (HPT) with up to 6 turns at room temperature (RT) and liquid nitrogen temperature (LNT),*** effects of temperature on grain refinement and microhardness variation were *** the samples after HPT processing at RT,the grain size reduced from 43 μm to 2.5 nm,and the Vickers microhardness increased from HV52.to ***,for the samples after HPT processing at LNT,the value of microhardness reached its maximum of HV150 near the center of the sample and it decreased to HV80 at the periphery *** observations revealed that HPT straining at LNT induced lamellar structures with thickness less than 100 nm appearing near the central region of the sample,but further deformation induced an inhomogeneous distribution of grain sizes,with submicrometer-sized grains embedded inside micrometer-sized *** submicrometer-sized grains with high dislocation density indicated their nonequilibrium *** the contrary,the micrometer-sized grains were nearly free of dislocation,without obvious deformation trace remaining in *** images demonstrated that the appearance of micrometer-sized grains is the result of abnormal grain growth of the deformed fine grains.

关键词： copper high pressure torsion (HPT) microstructure grain size microhardness cryogenic temperature

Annealing and strain rate effects on the mechanical behavior of ultrafine-grained iron produced by SPD

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Theoretical & Applied mechanics Letters 2011年第2期1卷 12-14页

作者： Fuping Yuan,~(a) Ping Jiang,~(b) and xiaolei wu~(c) {2. key Laboratory of nonlinear mechanics,institute of mechanics chinese academy of Science, beijing 100190,china state key Laboratory of {2. mechanics Institute of Mechanics Chinese Academy of Science Beijing 100190 China

Thermal stability and strain rate sensitivity of ultrafine-grained(UFG)Fe produced by severe plastic deformation(SPD)were *** UFG Fe was processed by equal-channel angular pressing(ECAP)via route *** 6 passes,the grain size of UFG Fe reaches 600 nm, as confirmed by means of electron back scatter diffraction(EBSD).Examination of micro-hardness and grain size of UFG Fe as a function of post-ECAP annealing temperature shows a transition from recovery to *** critical transition temperature is approximately 500℃,and the material has a bimodal structure after annealing at this *** behaviors of ECAP Fe and ECAP + annealing Fe were studied under both quasi-static and dynamic compressive *** UFG iron shows increased strength and reduced strain rate sensitivity compared with its coarse-grained *** appropriate post-ECAP annealing can increase strain hardening ability and cancel out thermal softening effect with only a small loss of strength under dynamic loading.

关键词： UFG/NC Fe ECAP EBSD thermal stability strain rate sensitivity

Observation of the Turbulent Burst near ASheared Air-Water Interface

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Communications in nonlinear Science and Numerical Simulation 1999年第2期4卷 94-99页

作者： Shuangfeng WANG Fu JIA Zhennan NIU Zhangzhi wu(institute of {2., chinese academy of sciences, beijing 100080, china)(state key Laboratory for Turbulence Research, Peking University, beijing 100871,china) institute of mechanics Chinese Academy of Sciences Beijing 100080 China

The turbulent burst under a sheared air-water interface was experimentally investigated using hydrogen bubble visualization technique. The surface shear wasimposed by an airflow over the water flow which was kept free from surface waves. Resultsshow that the wind shear has the main influence on the bursting events. At relativelyhigh shear rates, the flow near the interface is dominated primarily by intermittent bursting events. The general features of bursting processes are described in some detail. Theobserved bursting events show qualitative similarities with those occurring in near-wallturbulence. However, a few distinctive phenomena were also observed, including the existence of vertical vortices and thickening process of the boundary layer, which appear tobe associated with the Characteristics of air-water interface.

关键词： air-water interface turbulent burst flow-visualization

Parallelization strategies for resolved simulations of fluid-structure-particle interactions

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Applied Mathematics and mechanics(English Edition) 2024年第5期45卷 857-872页

作者： Jianhua QIN Fei LIAO Guodan DONG xiaolei YANG The state key Laboratory of {2. mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China Interdisciplinary Center for Fundamental and Frontier sciences Nanjing University of Science and TechnologyJiangyin 214443Jiangsu ProvinceChina School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China School of Engineering sciences University of Chinese Academy of SciencesBeijing 100049China

Fluid-structure-particle interactions in three spatial dimensions happen in many environmental and engineering *** paper presents the parallel algorithms for the hybrid diffuse and sharp interface immersed boundary(IB)method developed in our previous *** the moving structure modeled using the sharp interface IB method,a recursive box method is developed for efficiently classifying the background grid *** the particles modeled using the diffuse interface IB method,a‘master-slave’approach is *** the particle-particle interaction(PPI)and particle-structure interaction(PSI),a fast algorithm for classifying the active and inactive Lagrangian points,which discretize the particle surface,is developed for the‘dry’contact *** results show that the proposed recursive box method can reduce the classifying time from 52.econds to 0.3 *** parallel efficiency is obtained for cases with different particle ***,the lubrication model is utilized when a particle approaches a wall,enabling an accurate simulation of the rebounding phenomena in the benchmark particle-wall collision *** last,the capability of the proposed computational framework is demonstrated by simulating particle-laden turbulent channel flows with rough walls.

关键词： particle-resolved direct numerical simulation particle-laden flow complex geometry resolved fluid-structure-particle interaction(RFSPI) immersed boundary(IB)method

In Situ Synthesis of Nanocrystalline Intel-metallic Compound Layer during Surface Mechanical Attrition Treatment of Zirconium

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材料热处理学报 2004年第5期 1242-1246页

作者： SUN Cai-yun', Xffi Ji-jia ', wu Xiao-lei', HONG You-shi', LIU Gang \ LU Jian3, LU Ke2.1. state {2. Laboratory of nonlinear mechanics, institute of mechanics, chinese academy of sciences, beijing 100080, People's Republic of china 2. Shenyang National Laboratory for Materials sciences, institute of Metal Research, chinese academy of sciences, Shenyang 110016, People's Republic of china 3. LASMIS, University of Technical of Troyes, 10000, Troyes, France

The surface mechanical attrition treatment (SMAT) technique was developed to synthesize a nanocrystalline (NC) layer on the surface of metallic materials for upgrading their overall properties and performance. In this paper, by means of SMAT to a pure zirconium plate at the room temperature, repetitive multidirectional peening of steel shots (composition (wt%): 1C, ***, base Fe) severely deformed the surface layer. A NC surface layer consisting of the intermetallic compound FeCr was fabricated on the surface of the zirconium. The microstructure characterization of the surface layer was performed by using X-ray diffraction analysis, optical microscopy, scanning and transmission electron microscopy observations. The NC surface layer was about 2. urn thick and consisted of the intermetallic compound FeCr with an average grain size of 2.±10 nm. The deformation-induced fast diffusion of Fe and Cr from the steel shots into Zr occurred during SMAT, leading to the formation of intermetallic compound. In addition, the NC surface layer exhibited an ultrahigh nanohardness of 10.2.GPa.

关键词： nanocrystalline intermetallic compound surface layer deformation diffusion

A thermal-mechanical constitutive model for b-HMX single crystal and cohesive interface under dynamic high pressure loading

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Science china(Physics,mechanics & Astronomy) 2010年第2期53卷 218-226页

作者： wu YanQing & HUANG FengLei state {2. Laboratory of Explosion Science and Technology,beijing institute of Technology,beijing 100081,china state key Laboratory of Explosion Science and Technology Beijing Institute of Technology Beijing China

Due to the significant thermal-mechanical effects during hot spot formation in PBX explosives,a thermodynamic constitutive model has been constructed for HMX anisotropic single crystal subjected to dynamic impact loading. The crystal plasticity model based on dislocation dynamics theory was employed to describe the anisotropic plastic behavior along the preferential slip systems. A modified equation of state (EOS) was introduced into the constitutive equations through the decomposing stress tensor and the nonlinear elasticity for materials was taken into account. The one-dimensional strain impact simulations for HMX single crystal and quasi-bicrystal were performed respectively,in which the cohesive elements were inserted over the interface areas for the latter. The predicted particle velocities for the single crystal sample agreed well with the experimental results in the literature. Furthermore,the effects of crystal orientations,interface,misorientations on localized strain,stress and temperature distributions were predicted and discussed.

关键词： energetic single crystal dynamic high pressure crystal plasticity thermodynamics interfacial model

DEFORMATION TWINNING MECHANISMS IN NANOCRYSTALLINE NI

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DEFORMATION TWINNING MECHANISMS IN NANOCRYSTALLINE NI