Acta Mechanica Sinica
     Acta Mechanica Sinica
  Acta Mechanica Sinica--2012, 28 (3)   Published: 25 June 2012
Special papers on biomechanics
A numerical study of fluid injection and mixing under near-critical conditions
Hua-Guang Li, Xi-Yun Lu, Vigor Yang
Nitrogen injection under conditions close vicinity of the liquid-gas critical point is studied numerically. The fluid thermodynamic and transport properties vary drastically and exhibit anomalies in the near-critical regime. These anomalies can cause distinctive effects on heat-transfer and fluid-flow characteristics. To focus on the influence of thermodynamics on the flow field, a relatively low injection Reynolds number of 1750 is adopted. For comparisons, a reference case with the same config...
Tomographic PIV investigation of coherent structures in a turbulent boundary layer flow
Zhan-Qi Tang, Nan Jiang, Andreas Schröder, Reinhard Geisler
Tomographic particle image velocimetry was used to quantitatively visualize the three-dimensional coherent structures in the logarithmic region of the turbulent boundary layer in a water tunnel. The Reynolds number based on momentum thickness is Reθ=2460. The instantaneous velocity fields give evidence of hairpin vortices aligned in the streamwise direction forming very long zones of low speed fluid, which is flanked on either side by highspeed ones. Statistical support fo...
Wind induced deformation and vibration of a Platanus acerifolia leaf
Chuan-Ping Shao, Ye-Jun Chen, Jian-Zhong Lin
Deformation and vibration of twig-connected single leaf in wind is investigated experimentally. Results show that the Reynolds number based on wind speed and length of leaf blade is a key parameter to the aerodynamic problem. In case the front surface facing the wind and with an increase of Reynolds number, the leaf experiences static deformation, large amplitude and low frequency sway, reconfiguration to delta wing shape, flapping of tips, high frequency vibration of whole leaf blade, recovery ...
Two-phase micro- and macro-time scales in particle-laden turbulent channel flows
Bing Wang, Michael Manhart
The micro- and macro-time scales in two-phase turbulent channel flows are investigated using the direct numerical simulation and the Lagrangian particle trajectory methods for the fluid- and the particle-phases, respectively. Lagrangian and Eulerian time scales of both phases are calculated using velocity correlation functions. Due to flow anisotropy, micro-time scales are not the same with the theoretical estimations in large Reynolds number (isotropic) turbulence. Lagrangian macro-time scales ...
Fundamental solutions for axi-symmetric translational motion of a microstretch fluid
H.H. Sherief, M.S. Faltas, E.A. Ashmawy
The fundamental solution for the axi-symmetric translational motion of a microstretch fluid due to a concentrated point body force is obtained. A general formula for the drag force exerted by the fluid on an axi-symmetric rigid particle translating in it is then deduced. As an application to the obtained drag formula, this paper has discussed the problem of creeping translational motion of a rigid sphere in a microstretch fluid. The slip boundary condition on the surface of the spherical particl...
Lagrangian-based investigation of multiphase flows by finite-timeLyapunov exponents
Jia-Ning Tang, Chien-Chou Tseng, Ning-Fei Wang
Multiphase flows are ubiquitous in our daily life and engineering applications. It is important to investigate the flow structures to predict their dynamical behaviors effectively. Lagrangian coherent structures (LCS) defined by the ridges of the finite-time Lyapunov exponent (FTLE) is utilized in this study to elucidate the multiphase interactions in gaseous jets injected into water and time-dependent turbulent cavitation under the framework of Navier-Stokes flow computations.
For the gaseou...
Effects of boundary slippage on thin-film lubrication between two nonparallel plane plates
Shu-Hao Ban, Xiao-Yan Li
Hydrodynamic lubrications between two plane plates with an intersection angle θ have been investigated using the boundary slippage theory, and relations are obtained between dimensionless pressures and coordinate x, between bearing capacity, friction force, friction coefficient and dimensionless slipping size factor. The results show that bearing capacity of two plane plates without boundary slippage significantly increases with increasing intersection angle θ when 0 < θ ...
On the time development of dispersion in electroosmotic flow througha rectangular channel
Suvadip Paul, Chiu-On Ng
This is an analytical study on the time development of hydrodynamic dispersion of an inert species in electroosmotic flow through a rectangular channel. The objective is to determine how the channel side walls may affect the dispersion coefficient at different instants of time. To this end, the generalized dispersion model, which is valid for short and long times, is employed in the present study. Analytical expressions are derived for the convection and dispersion coefficients as functions of t...
Experimental investigation on flow modes of electrospinning
Ting Si, Guang-Bin Li, Xing-Xing Chen, Rui-Jun Tian, Xie-Zhen Yin
Electrospinning experiments are performed by using a set of experimental apparatus, a stroboscopic system is adopted for capturing instantaneous images of the cone-jet configuration. The cone and the jet of aqueous solutions of polyethylene oxide (PEO) are formed from an orifice of a capillary tube under the electric field. The viscoelastic constitutive relationship of the PEO solution is measured and discussed. The phenomena owing to the jet instability are described, five flow modes and corres...
Steady rotation of a composite sphere in a concentric spherical cavity
D. Srinivasacharya, M. Krishna Prasad
The problem of steady rotation of a composite sphere located at the centre of a spherical container has been investigated. A composite particle referred to in this paper is a spherical solid core covered with a permeable spherical shell. The Brinkman's model for the flow inside the composite sphere and the Stokes equation for the flow in the spherical container were used to study the motion. The torque experienced by the porous spherical particle in the presence of cavity is obtained. The wall c...
Local resonance phononic band gaps in modified two-dimensional lattice materials
Wei Liu, Ji-Wei Chen, Xian-Yue Su
In this paper, modified two-dimensional periodic lattice materials with local resonance phononic band gaps are designed and investigated. The design concept is to introduce some auxiliary structures into conventional periodic lattice materials. Elastic wave propagation in this kind of modified two-dimensional lattice materials is studied using a combination of Bloch’s theorem with finite element method. The calculated frequency band structures of illustrative modified square lattice materials re...
Crack patterns corresponding to the residual strength plateau of ceramics subjected to thermal shock
H.-L. Hou, X.-F. Wu, P. Yan, F. Song, J. Li, C.-P. Jiang
The formation mechanism of the residual strength plateau of ceramics subjected to thermal shock is addressed. A set of thermal shock experiments of 99Al2O3 are conducted, where the thin specimens of 1 mm ? 10 mm ? 50 mm exhibit parallel through edge cracks, and thus permit quantitative measurements of the crack patterns. The cracks evolve with the severity of thermal shock. It is found that there is a correlation between the length and density of the thermal shock cracks. T...
The three-dimension model for the rock-breaking mechanism of disc cutter and analysis of rock-breaking forces
Zhao-Huang Zhang, Fei Sun
To study the rock deformation with three-dimensional model under rolling forces of disc cutter, by carrying out the circular-grooving test with disc cutter rolling around on the rock, the rock mechanical behavior under rolling disc cutter is studied, the mechanical model of disc cutter rolling around the groove is established, and the theory of single-point and double-angle variables is proposed. Based on this theory, the physics equations and geometric equations of rock mechanical behavior unde...
On stability of elastic domain during isothermal solid-solid phase transformation in a tube configuration
Liang Dong, Qing-Ping Sun
Under isothermal quasi-static stretching the phase transition of a superelastic NiTi tube involves the formation (during loading) and vanishing (in unloading) of a high strain (martensite) domain. The two events are accompanied by a rapid stress drop/rise due to the formation/vanishing of domain fronts. From a thermodynamic point of view, both are instability phenomena that occur once the system reaches its critical state. This paper investigates the stability of a shrinking cylindrical domain i...
Static and dynamic snap-through behaviour of an elastic spherical shell
D. Karagiozova, X.-W. Zhang, T.-X. Yu
The deformation and snap-through behaviour of a thin-walled elastic spherical shell statically compressed on a flat surface or impacted against a flat surface are studied theoretically and numerically in order to estimate the influence of the dynamic effects on the response. A table tennis ball is considered as an example of a thin-walled elastic shell. It is shown that the increase of the impact velocity leads to a variation of the deformed shape thus resulting in larger deformation energy. The...
Factors influencing particle agglomeration during solid-state sintering
Chao Wang, Shao-Hua Chen
Discrete element method (DEM) is used to study the factors affecting agglomeration in three-dimensional copper particle systems during solid-state sintering. A new parameter is proposed to characterize agglomeration. The effects of a series of factors are studied, including particle size, size distribution, inter-particle tangential viscosity, temperature, initial density and initial distribution of particles on agglomeration. We find that the systems with smaller particles, broader particle siz...
A glance on the effects of temperature on axisymmetric dynamic behavior of multiwall carbon nanotubes
S. T. Talebian, M. Tahani, M. H. Abolbashari, S. M. Hosseini
In this paper the effects of temperature on the radial breathing modes (RBMs) and radial wave propagation in multiwall carbon nanotubes (MWCNTs) are investigated using a continuum model of multiple elastic isotropic shells. The van der Waals forces between tubes are simulated as a nonlinear function of interlayer spacing of MWCNTs. The governing equations are solved using a finite element method. A wide range of innermost radius-to-thickness ratio of MWCNTs is considered to enhance the investiga...
Analytical modeling of static behavior of electrostatically actuatednano/micromirrors considering van der Waals forces
Hamid Moeenfard, Mohammad Taghi Ahmadian
In this paper, the effect of van der Waals (vdW) force on the pull-in behavior of electrostatically actuated nano/micromirrors is investigated. First, the minimum potential energy principle is utilized to find the equation governing the static behavior of nano/micromirror under electrostatic and vdW forces. Then, the stability of static equilibrium points is analyzed using the energy method. It is found that when there exist two equilibrium points, the smaller one is stable and the larger one is...
Influences of oscillatory structural forces on dewetting of nanoparticle-laden ultra-thin films
Guo-Hui Hu
To understand the influences of nanoparticles on dewetting in ultra-thin films, both linear stability theory and numerical simulations are performed in the present study, with the consideration of oscillatory structural (OS) forces. Long scale approximation is utilized to simplify the hydrodynamic and diffusion equations to a nonlinear system for film thickness and nanoparticle concentration. Results show that the presence of nanoparticles generally suppresses the dewetting process. Two physical...
Multiscale modeling of heterogeneous propellants from particle packing tograin failure using a surface-based cohesive approach
Shi-Jun Zhi, Bing Sun, Jian-Wei Zhang
In the present work, a computational framework is established for multiscale modeling and analysis of solid propellants. A packing algorithm, considering the ammonium perchlorate (AP) and aluminum (Al) particles as spheres or discs is developed to match the size distribution and volume fraction of solid propellants. A homogenization theory is employed to compute the mean stress and strain of a representative volume element (RVE). Using the mean results, a suitable size of RVE is decided. Without...
Modeling rock failure using the numerical manifold method followed bythe discontinuous deformation analysis
You-Jun Ning, Xin-Mei An, Qing Lü, Guo-Wei Ma
A complete rock failure process usually involves opening/sliding of preexisting discontinuities as well as fracturing in intact rock bridges to form persistent failure surfaces and subsequent motions of the generated rock blocks. The recently developed numerical manifold method (NMM) has potential for modelling such a complete failure process. However, the NMM suffers one limitation, i.e., unexpected material domain area change occurs in rotation modelling. This problem can not be easily solved ...
A comparison of electromigration failure of metal lines with fracture mechanics
Hiroyuki Abé, Mikio Muraoka, Kazuhiko Sasagawa, Masumi Saka
Atoms constructing an interconnecting metal line in a semiconductor device are transported by electron flow in high density. This phenomenon is called electromigration, which may cause the line failure. In order to characterize the electromigration failure, a comparison study is carried out with some typical phenomena treated by fracture mechanics for thin and large structures. An example of thin structures, which have been treated by fracture mechanics, is silica optical fibers for communicatio...
Differential quadrature time element method for structural dynamics
Yu-Feng Xing, Jing Guo
An accurate and efficient differential quadrature time element method (DQTEM) is proposed for solving ordinary differential equations (ODEs), the numerical dissipation and dispersion of DQTEM is much smaller than that of the direct integration method of single/multi steps. Two methods of imposing initial conditions are given, which avoids the tediousness when derivative initial conditions are imposed, and the numerical comparisons indicate that the first method, in which the analog equations of ...
Multi-symplectic method for the generalized (2+1)-dimensional KdV-mKdV equation
Wei-Peng Hu, Zi-Chen Deng, Yu-Yue Qin, Wen-Rong Zhang
In the present paper, a general solution involving three arbitrary functions for the generalized (2+1)-dimensional KdV-mKdV equation, which is derived from the generalized (1+1)-dimensional KdV-mKdV equation, is first introduced by means of the Wiess, Tabor, Carnevale (WTC) truncation method. And then multi-symplectic formulations with several conservation laws taken into account are presented for the generalized (2+1)-dimensional KdV-mKdV equation based on the multi-symplectic theory of Bridges...
Axial vibration analysis of nanocones based on nonlocal elasticity theory
Shu-Qi Guo, Shao-Pu Yang
Carbon nanocones have quite fascinating electronic and structural properties, whose axial vibration is seldom investigated in previous studies. In this paper, based on a nonlocal elasticity theory, a nonuniform rod model is applied to investigate the small-scale effect and the nonuniform effect on axial vibration of nanocones. Using the modified Wentzel-Brillouin-Kramers (WBK) method, an asymptotic solution is obtained for the axial vibration of general nonuniform nanorods. Then, using similar p...
The improved element-free Galerkin method for three-dimensional wave equation
Zan Zhang, Dong-Ming Li, Yu-Min Cheng, Kim Moew Liew
The paper presents the improved element-free Galerkin (IEFG) method for three-dimensional wave propagation. The improved moving least-squares (IMLS) approximation is employed to construct the shape function, which uses an orthogonal function system with a weight function as the basis function. Compared with the conventional moving least-squares (MLS) approximation, the algebraic equation system in the IMLS approximation is not ill-conditioned, and can be solved directly without deriving the inve...
Simulation of thermoacoustic waves by a pressure-based algorithm for compressible flows
Wei Li, Qi-Sheng Chen
A modified SIMPLEC method which can solve compressible flows at low Mach number is introduced and used to study thermoacoustic waves induced by a rapid change of temperature at a solid wall and alternating-direction flows generated by thermoacoustic effects in a tapered resonator. The results indicate that the algorithm adopted in this paper can be used for calculating compressible flows and thermoacoustic waves. It is found that the pressure and velocity in the resonator behave as standing wave...
Parametric study on single shot peening by dimensional analysis method incorporated with finite element method
Xian-Qian Wu, Xi Wang, Yan-Peng Wei, Hong-Wei Song, Chen-Guang Huang
Shot peening is a widely used surface treatment method by generating compressive residual stress near the surface of metallic materials to increase fatigue life and resistance to corrosion fatigue, cracking, etc. Compressive re-sid-ual stress and dent profile are important factors to evaluate the effectiveness of shot peening process. In this paper, the influence of dimensionless parameters on maximum compressive residual stress and maximum depth of the dent were investigated. Firstly, dimension...
Controllability of an underactuated spacecraft with one thruster under disturbance
Dong-Xia Wang, Ying-Hong Jia, Lei Jin, Hai-Chao Gui, Shi-Jie Xu
For an underactuated spacecraft using only one thruster, the attitude controllability with respect to the orbit frame is studied in the presence of periodical oscillation disturbance, which provides a preconditional guide on designing control law for underactuated attitude control system. Firstly, attitude dynamic model was established for an underactuated spacecraft, and attitude motion was described using the special orthogonal group (SO (3)). Secondly, Liouville theorem was used to confirm th...
Optimal design of vibration absorber using minimax criterion with simplified constraints
Jie Fang, Shi-Min Wang, Qi Wang
In this paper, a minimax design of damped dynamic vibration absorber for a damped primary system is investigated to minimize the vibration magnitude peaks. Moreover, to reduce the sensitivity of the primary system response to variations of the forcing frequency for a two-degree-of-freedom system, the primary system should have two equal resonance magnitude peaks. To meet this requirement, a set of simplified constraint equations including distribution characteristics of the resonant frequencies ...
A-posteriori error estimation for second order mechanical systems
Thomas Ruiner, Jörg Fehr, Bernard Haasdonk, Peter Eberhard
One important issue for the simulation of flexible multibody systems is the reduction of the flexible bodies degrees of freedom. As far as safety questions are concerned knowledge about the error introduced by the reduction of the flexible degrees of freedom is helpful and very important. In this work, an a-posteriori error estimator for linear first order systems is extended for error estimation of mechanical second order systems. Due to the special second order structure of mechanical systems,...
Large deflections of non-prismatic nonlinearly elastic cantilever beams subjected to non-uniform continuous load and a concentrated load at the free end
Miha Brojan, Matjaz Cebron, Franc Kosel
This work studies large deflections of slender, non-prismatic cantilever beams subjected to a combined loading which consists of a non-uniformly distributed continuous load and a concentrated load at the free end of the beam. The material of the cantilever is assumed to be nonlinearly elastic. Different nonlinear relations between stress and strain in tensile and compressive domain are considered. The accuracy of numerical solutions is evaluated by comparing them with results from previous studi...
Numerical analysis of added mass and damping of floating production,storage and offloading system
Ke Wang, Xi Zhang, Zhi-Qiang Zhang, Wang Xu
An integral equation approach is utilized to investigate the added mass and damping of floating production, storage and offloading system (FPSO system). Finite water depth Green function and higher-order boundary element method are used to solve integral equation. Numerical results about added mass and damping are presented for odd and even mode motions of FPSO. The results show robust convergence in high frequency range and can be used in wave load analysis for FPSO designing and operation.
Experimental and simulation optimization analysis of the Whipple shields against shaped charge
G. Hussain, A. Hameed, I. Horsfall, P. Barton, A. Q. Malik
Occasionally, the Whipple shields are used for the protection of a space station and a satellite against the meteoroids and orbital debris. In the Whipple shields each layer of the shield depletes part of high speed projectile energy either by breaking the projectile or absorbing its energy. Similarly, this investigation uses the Whipple shields against the shaped charge to protect the light armour such as infantry fighting vehicles with a little modification in their design. The unsteady multip...
High order symplectic conservative perturbation method for time-varying Hamiltonian system
Ming-Hui Fu, Ke-Lang Lu, Lin-Hua Lan
This paper presents a high order symplectic conservative perturbation method for linear time-varying Hamiltonian system. Firstly, the dynamic equation of Hamiltonian system is gradually changed into a high order perturbation equation, which is solved approximately by resolving the Hamiltonian coefficient matrix into a “major component” and a “high order small quantity” and using perturbation transformation technique, then the solution to the original equation of Hamiltonian system is determined ...
Free energy calculation of single molecular interaction using Jarzynski's identity method: the case of HIV-1 protease inhibitor system
De-Chang Li, Bao-Hua Ji
Jarzynski' identity (JI) method was suggested a promising tool for reconstructing free energy landscape of biomolecular interactions in numerical simulations and experiments. However, JI method has not yet been well tested in complex systems such as ligand-receptor molecular pairs. In this paper, we applied a huge number of steered molecular dynamics (SMD) simulations to dissociate the protease of human immunodeficiency type I virus (HIV-1 protease) and its inhibitors. We showed that because of ...
Effects of fluid recirculation on mass transfer from the arterial surface toflowing blood
Zhi-Guo Zhang, Xi-Wen Zhang, Ying-Xi Liu
The effect of disturbed flow on the mass transfer from arterial surface to flowing blood was studied numerically, and the results were compared with that of our previous work. The arterial wall was assumed to be viscoelastic and the blood was assumed to be incompressible and non-Newtonian fluid, which is more close to human arterial system. Numerical results indicated that the mass transfer from the arterial surface to flowing blood in regions of disturbed flow is positively related with the wal...
Discussion on “Thermomagnetic viscoelastic responses in a functionally graded hollow structure” [Acta Mechanica Sinica 27(4), 567-577, (2011)]
Uğur Güven
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