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An experimental investigation of dual-resonant and non-resonant responses for vortex-induced vibration of a long slender cylinder

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Science China(Physics,mechanics & Astronomy) 2014年第2期57卷 321-329页

作者： WU XiaoDong GE Fei HONG YouShi College of mechanics Taiyuan University of Technology State key laboratory of nonlinear mechanics Institute of MechanicsChinese Academy of Sciences

Experimental results of the dual-resonant and non-resonant responses are presented for vortex-induced vibrations(VIV)of a long slender *** cylinder has a diameter of 10mm and a length of 3.31 m,giving an aspect ratio of *** cylinder was towed by a carriage with the velocity up to 1.5 m/s,with the Reynolds number varying from 2500 to *** different weights were used to provide the initial *** resonance means that resonance occurs simultaneously in both the cross-flow(CF)and in-line(IL)*** experiments were conducted in two *** the first stage,dual-resonant dynamic features of the cylinder subjected to vortex-induced excitation were *** features of CF and IL vibration amplitude,motion orbits,phase angle differences,dominant frequencies and mode order numbers are *** the second stage of the experiments,particular emphasis was placed on non-resonant dynamic *** variation of multi-mode modal displacement amplitudes was investigated in detail.

关键词： vortex-induced vibrations long slender cylinder dual-resonant responses non-resonant responses

THE UNIQUE PROPERTIES OF THE SOLID-LIKE CONFINED LIQUID FILMS:A LARGE SCALE MOLECULAR DYNAMICS SIMULATION APPROACH

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Acta Mechanica Solida Sinica 2011年第2期24卷 101-116页

作者： Fengchao Wang Yapu Zhao State key laboratory of nonlinear mechanics Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China

The properties of the confined liquid are dramatically different from those of the bulk state, which were reviewed in the present work. We performed large-scale molecular dynamics simulations and full-atom nonequilibrium molecular dynamics simulations to investigate the shear response of the confined simple liquid as well as the n-hexadecane ultrathin films. The shear viscosity of the confined simple liquid increases with the decrease of the film thickness. Apart from the well-known ordered structure, the confined n-hexaxiecane exhibited a transition from 7 layers to 6 in our simulations while undergoing an increasing shear velocity. Various slip regimes of the confined n-hexadecane were obtained. Viscosity coefficients of individual layers were examined and the results revealed that the local viscosity＇coefficient varies with the distance from the wall. The individual n-hexadecane layers showed the shear-thinning behaviors which can be correlated with the occurrence of the slip. This study aimed at elucidating the detailed shear response of the confined liquid and may be used in the design and application of microand nano-devices.

关键词： confined liquid solid-like shear-thinning slip large scale molecular dynamics simulation

Thermodynamic properties and constitutive relations of crystals at finite temperature

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Science China(Physics,mechanics & Astronomy) 2012年第6期55卷 918-926页

作者： TANG QiHeng WANG TzuChiang SHANG BaoShuang LIU Feng State key laboratory of nonlinear mechanics Institute of MechanicsChinese Academy of SciencesBeifing 100190China

The dynamics equation for each individual atom is established directly around the equilibrium state of the system of N atoms based on the inter-atomic potential energy of EAM *** the theory of lattice dynamics and periodical boundary condition,the 3N×3N stiffness matrix in eigen equations of vibration frequencies for a parallelepiped crystal is reduced to a 3n×3n matrix of eigen equations of vibration frequencies for a unit *** constitutive relation of the crystal at finite temperature is extracted based on the quantum-mechanical *** thermodynamic properties and the stress-strain relationships of crystal Cu with large plastic deformation at different temperatures are calculated,the calculation results agree well with experimental data.

关键词： lattice wave theory molecular dynamics thermodynamic properties constitutive model interatomic potential

SELF-INSTABILITY AND BENDING BEHAVIORS OF NANO PLATES

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Acta Mechanica Solida Sinica 2009年第6期22卷 630-643页

作者： Zhiqiao Wang Yapu Zhao State key laboratory of nonlinear mechanics Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China

This paper aims at investigating the size-dependent self-buckling and bending behaviors of nano plates through incorporating surface elasticity into the elasticity with residual stress fields. In the absence of external loading, positive surface tension induces a compressive residual stress field in the bulk of the nano plate and there may be self-equilibrium states corresponding to the plate self-buckling. The self-instability of nano plates is investigated and the critical self-instability size of simply supported rectangular nano plates is determined. In addition, the residual stress field in the bulk of the nano plate is usually neglected in the existing literatures, where the elastic response of the bulk is often described by the classical Hooke＇s law. The present paper considered the effect of the residual stress in the bulk induced by surface tension and adopted the elasticity with residual stress fields to study the bending behaviors of nano plates without buckling. The present results show that the surface effects only modify the coefficients in corresponding equations of the classical Kirchhoff plate theory.

关键词： nano plates self-buckling surface tension residual stress

Plastic deformation of nanocrystalline nickel

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Science China(Technological Sciences) 2009年第8期52卷 2216-2221页

作者： WU XiaoLei State key laboratory of nonlinear mechanics, Institute of mechanics, Chinese Academy of Sciences, Beijing 100190, China State key laboratory of nonlinear mechanics Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China

A high-resolution electron microscopy study has uncovered the plastic behavior of accommodating large strains in nanocrystalline (NC) Ni subject to cold rolling at liquid nitrogen temperature. The activation of grain-boundary-mediated-plasticity is evidenced in NC-Ni, including twinning and formation of stacking fault via partial dislocation slips from the grain boundary. The formation and storage of 60? full dislocations are observed inside NC-grains. The grain/twin boundaries act as the barriers of dislocation slips, leading to dislocation pile-up, severe lattice distortion, and formation of sub-grain boundary. The vicinity of grain/twin boundary is where defects preferentially accumulate and likely the favorable place for onset of plastic deformation. The present results indicate the heterogeneous and multiple natures of accommodating plastic strains in NC-grains.

关键词： nanocrystalline metal plastic deformation deformation twinning dislocation microstructure

Feasibility study on buoyancy-weight ratios of a submerged floating tunnel prototype subjected to hydrodynamic loads

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Acta Mechanica Sinica 2015年第5期31卷 750-761页

作者： Xu Long Fei Ge Youshi Hong School of mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical University State key laboratory of nonlinear mechanics Institute of MechanicsChinese Academy of Sciences

The research progress of a novel traffic solution,a submerged floating tunnel（SFT）,is reviewed in terms of a study approach and loading *** existing publications,the buoyancy-weight ratio（BWR） is usually ***,BWR is a critical structural parameter that tremendously affects the dynamic behaviour of not only the tunnel tube itself but also the cable *** the context of a SFT prototype（SFTP） project in Qiandao Lake（Zhejiang Province,China）,the importance of BWR is illustrated by finite element analysis and subsequently,an optimized BWR is proposed within a reasonable range in the present *** the numerical model,structural damping is identified to be of *** damping and the corresponding Rayleigh coefficients are attained through a sensitivity study,which shows that the adopted damping ratios are fairly suitable for ***,the human sense of security is considered by quantifying the comfort index,which helps further optimize BWR in the SFTP structural parameter design.

关键词： Submerged floating tunnel Buoyancy-weight ratio Water wave and current loads Dynamic response Human security sense Comfort index

Numerical study of pile-up in bulk metallic glass during spherical indentation

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Science China(Physics,mechanics & Astronomy) 2008年第4期51卷 379-386页

作者： AI Ke DAI LanHong State key laboratory of nonlinear mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100080China

Pile-up around indenter is usually observed during instrumented indentation tests on bulk metallic glass. Neglecting the pile-up effect may lead to errors in evaluating hardness,Young’s modulus,stress-strain response,etc. Finite element analysis was employed to implement numerical simulation of spherical indentation tests on bulk metallic glass. A new model was proposed to describe the pile-up effect. By using this new model,the contact radius and hardness of Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass were obtained under several different indenter loads with pile-up,and the results agree well with the data generated by numerical simulation.

关键词： bulk metallic glass spherical indenter pile-up contact radius hardness

DNS of compressible turbulent boundary layer around a sharp cone

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Science China(Physics,mechanics & Astronomy) 2008年第6期51卷 699-714页

作者： LI XinLiang FU DeXun MA YanWen State key laboratory of nonlinear mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100080China

Direct numerical simulation of the turbulent boundary layer over a sharp cone with 20° cone angle (or 10° half-cone angle) is performed by using the mixed seventh- order up-wind biased finite difference scheme and sixth-order central difference scheme. The free stream Mach number is 0.7 and free stream unit Reynolds number is 250000/inch. The characteristics of transition and turbulence of the sharp cone boundary layer are compared with those of the flat plate boundary layer. Statistics of fully developed turbulent flow agree well with the experimental and theoretical data for the turbulent flat-plate boundary layer flow. The near wall streak-like structure is shown and the average space between streaks (normalized by the local wall unit) keeps approximately invariable at different streamwise locations. The turbulent energy equation in the cylindrical coordinate is given and turbulent en-ergy budget is studied. The computed results show that the effect of circumferen-tial curvature on turbulence characteristics is not obvious.

关键词： direct numerical simulation boundary layer transition sharp-cone turbulent kinetic energy budget

Anisotropic Rock Poroelasticity Evolution in Ultra-low Permeability Sandstones under Pore Pressure,Confining Pressure,and Temperature:Experiments with Biot's Coefficient

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Acta Geologica Sinica(English Edition) 2021年第3期95卷 937-945页

作者： DU Shuheng State key laboratory of nonlinear mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China

This study aimed to show anisotropic poroelasticity evolution in ultra-low permeability reservoirs under pore pressure,confining pressure,and *** groups of experiments examining Biot's coefficient under different conditions were carried *** showed that Biot's coefficient decreased with increased pore pressure,and the variation trend is linear,but the decreasing rate is variable between ***'s coefficient increased with increased confining pressure;the variation trend is linear,but the increasing rate varies by material as ***,Biot's coefficient remains stable with increased ***,clay mineral content,particle arrangement,and pore arrangement showed impacts on Biot's *** strong hydrophilic clay minerals,expansion in water could result in a strong surface adsorption reaction,which could result in an increased fluid bulk modulus and higher Biot's *** skeleton minerals with strong lipophilicity,such as quartz and feldspar,increased oil saturation will also result in an adsorption reaction,leading to increased fluid bulk modulus and a higher Biot's *** study's conclusions provide evidence of poroelasticity evolution of ultra-low permeability and help the enhancing oil recovery(EOR)process.

关键词： Biot's coefficient ultra-low permeability pore pressure confining pressure temperature