Table of Content

    25 May 2008, Volume 40 Issue 3
    Research paper
    Hillslope soil erosion process model for natural rainfall events
    2008, 40(3):  0-0.  DOI: 10.6052/0459-1879-2008-3-2006-329
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    Based on the momentum theorem and water-balance principle, this paper has derived the basic equations of slope runoff. Soil erosion by raindrop splash and runoff are discussed, and hillslope soil erosion processes model was established. Finally, the model was solved by numerical solution considering the common solution-determining conditions, from which not only runoff and soil erosion yield but also their processes can be obtained. The model is validated by using observation data of Soil Conservation Ecological Science & Technology Demonstration Park of Jiangxi Province. Results show that the maximum relative error between the computation and observation values of the slop runoff processes is 10% while the maximum relative error between the computation and observation values of hillslope soil erosion processes is 9.2%. This indicates that the model is conceptually realistic reasonable and offers a feasible approach for research on soil erosion process. Key words overland flow﹒raindrop splash﹒runoff erosion﹒process﹒numerical solution
    Test gas contamination induced by the interaction of shock/boundary layer in shock tunnels
    Jinping Li Heng Feng Zonglin Jiang
    2008, 40(3):  289-296.  DOI: 10.6052/0459-1879-2008-3-2007-110
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    A investigation on the interactions among the reflected-shock, boundary layer and contact region in the detonation-driven shock tunnel was carried out by applying Navier-Stokes equations in a multicomponent system and the dispersion controlled dissipative (DCD) scheme. In addition, the physical mechanism of test gas contamination caused by the wall jet was analyzed, which dramatically reduces the experimental duration in a shock tunnel. The numerical results indicated a simple and effective method of installing to increase the experimental duration.
    the dynamics theory on the solidification of liquid droplets
    Yongqiang Chen Jianjun Xu
    2008, 40(3):  297-305.  DOI: 10.6052/0459-1879-2008-3-2007-496
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    The present paper develops a simplified Liquid-Solid-Gas-Fog (LSGF) model in the solidification of dispersed liquid droplets on the basis of mean field concept to obtain the uniformly valid asymptotic solution of the initial value problem at small supercooling. The results show that the whole dynamics process can be divided into two stages, the transient transition stage and the solidification stage. In the transient stage without phase transition, the initial temperature distribution prescribed in the system is quickly to be special spatial. In the solidification stage, there is the solid/liquid phase conversion process till to the vanish of the liquid phase. In addition, the case of the liquid copper droplets is simulated to obtain the duration and the temperature distribution of the solidification under various growth conditions.
    Hall effects in three-dimensional MHD generator
    Haoyu Lv Lee Chun-Hian Haitao Dong Gang Chen
    2008, 40(3):  306-314.  DOI: 10.6052/0459-1879-2008-3-2007-293
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    A numerical procedure for analyzing the MHD flows in the MHD generator of the bypass scramjet engine was developed in the present study by applying a five-equation model associated with non-ideal MHD flows at low magnetic Reynolds number. In the numerical procedure, an entropy condition scheme was applied for solving the non-homogeneous Navier-Stokes equations and an SOR method for solving the elliptic equation governed the electrical potential. The Hall effects on the MHD flow in the MHD generator were studied numerically. E-beams were shown as the ionizer to provide the effective and stable conductivity in the MHD flows. The numerical results indicated that the Hall effects might make the distortions on the flow and electric fields in the MHD generator to induce unstable secondary flow, and non-uniform Joule heating. In addition, The performance parameters of the MHD generator were obtained numerically to reveal that the Hall effects may deteriorate the performance of MHD generator.
    Characteristics of supercavitating flows around a hydrofoil
    Xiangbin Li Guoyu Wang Mindi Zhang Shuyan Liu
    2008, 40(3):  315-322.  DOI: 10.6052/0459-1879-2008-3-2006-568
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    Supercavitation around a hydrofoil is studied experimentally to address the flowing characteristics. A high-speed video camera is used to visualize the flow structures under different cavitation numbers. The digital particle image velocimetry (DPIV) is employed to measure the velocity fields. The bubbles among the cavitating fields are used as the tracer particles to survey the velocity distribution inside the cavity and improve the tracking capability of the tracer particles. The results show that three distinct supercavitating flow regimes can be observed with the decreasing cavitation numbers, in which the cavitation structure varies with the distribution of the water-vapor mixing phase and vapor phase. A large velocity gradient exists around the interface between the cavitation area and the free stream. In the cavitation area, the lower-velocity region moves from the foil's middle part to the downstream with the decrease of the cavitation number. The fluid velocity is low in the water-vapor mixture region, while with the similar distribution in the free stream and the vapor region.
    Study on flow past a nano circular cylinders with different Reynolds numbers
    Yinshi Li Yaling He Jie Sun Wenquan Tao
    2008, 40(3):  323-330.  DOI: 10.6052/0459-1879-2008-3-2007-205
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    The steady cross-flow past a circular cylinder in the low Reynolds numbers was investigated using non-equilibrium molecular dynamics simulations with the Lennard--Jones potential. The results showed three basic flow patterns in microscale, different from those in macroscale. The flow behind the circular cylinder is symmetric, nonseparated and steady when $Re<12$. Periodic shedding and the oscillation of vortices are observed when $Re>20$. When the stream velocity is higher than the local sound speed, a cavity in the downstream adjacent to the cylinder forms. Asymmetric vortices appears as a transitional range when $12
    Wrinkling analysis of space inflatable membrane structures
    Changguo Wang Xingwen Du Xiaodong He
    2008, 40(3):  331-338.  DOI: 10.6052/0459-1879-2008-3-2006-374
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    In this paper, the wrinkling analysis of space inflatable membrane structure was performed with the application of the contraction factor, the stress condition and wrinkling characteristic. The parameter of the contraction factor was introduced to show the contraction in the direction of texture, not the concept of the Poisson's ratio. The stress field and deformation of the wrinkled inflatable membrane structure were obtained. A deep discussion on the relationship between the Poisson's ratio and the contraction factor. Was carried out and the compatibility condition of the deformation was redefined. Furthermore, the 2-D wrinkling analytical method was extended into the case of the 3-D inflated structures. The flexural wrinkling of an inflated cylinder tube was analyzed to obtain the relationship between the critical wrinkling and the structural or mechanical parameters. The theoretical results were quantitatively verified and well agreed with the experimental results.
    A sensitive precursor to catastrophic failure in heterogeneous brittle materials
    Shengwang Hao Ju Sun
    2008, 40(3):  339-344.  DOI: 10.6052/0459-1879-2008-3-2007-552
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    In general, there are two failure modes in heterogeneous brittle materials, the gradual failure and the catastrophic failure. The paper analyses the differences between the gradual failure and the catastrophic failure based on statistical mesoscopic damage mechanics. The results show that the ratio of the released elastic energy to the damage dissipative energy can be served as a sensitive precursor of catastrophe. Furthermore the value of the non-dimensional ratio has a similar tendency to be 1 with different responses in the two failure modes, that is, the response function R always decreases in the gradual mode, while increases and tends to be infinite at the catastrophic point of the failure.
    The relationship between orthogonal static stresses in a plate and lamb wave velocity in an arbitrary direction
    Jun Wang Yanguan Wang
    2008, 40(3):  345-354.  DOI: 10.6052/0459-1879-2008-3-2007-033
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    A general dispersion equation for Lamb waves in an arbitrary direction was derived in an isotropic hyperelastic plate subjected to orthogonal static stresses with wavelet analysis. The relationship among Lamb wave velocity, orthogonal static stresses and frequency was analyzed in the present study. In addition, we discussed the relationship between Lamb wave velocity and uniaxial static stress with numerical method. The results provides the theoretical basis for Lamb wave applied to the stress measurement in thin plate.
    Development on the visco-elastic constitutive model of cardiac muscle based on experiment
    Hongrong Fang Tao Tang Xiangming Zhang Zhuo Zhuang
    2008, 40(3):  355-363.  DOI: 10.6052/0459-1879-2008-3-2007-187
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    Mechanical property data of canine cardiac muscle were experimentally obtained in the present study. In addition, finite element simulations were carried out for the uniaxial tension test and the relaxation test of canine cardiac muscle. The nonlinear elastic and viscous parameters of cardiac muscle are acquired to develop the nonlinear viscoelastic constitution of cardiac muscle for passive force. Furthermore, user material subroutine VUMAT in the finite element software ABAQUS is developed for the simulation of the numerical heart.
    Mechanical properties of plain high-strength high-performance concrete under biaxial compression after exposure to high temperatures
    Zhenjun He Yupu Song
    2008, 40(3):  364-374.  DOI: 10.6052/0459-1879-2008-3-2007-211
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    This study aims to generate the mechanical response of plain high-strength high-performance concrete (HSHPC) subjected to biaxial compressive loading at seven stress ratios, $\alpha = \sigma _{2} : \sigma_{ 3}, $-0.00: -1, -0.20: -1, -0.30: -1, -0.40: -1, -0.50: -1, -0.75: -1, -1.00: -1$, after exposure to the temperature of 20${^\circ}$C, 200${^\circ}$C, 300${^\circ}$C, 400${^\circ}$C, 500${^\circ}$C and 600${^\circ}$C, using the true-triaxial loading system. The biaxial static compressive strengths, strains at the peak stress and the stress-strain curves are obtained to analyze the influence of the temperature and the stress ratio. Failure modes of plain HSHPC specimens are observed. The experimental results show that the biaxial compressive strength of HSHPC is more sensitive to the stress ratio and the exposure treatment to high temperatures than the uniaxial compressive strength. The Kupfer-Gerstle failure criterion for plain HSHPC is developed with the parameters of the temperature and stress ratio.
    Retrieval control of an electro-dynamic tethered satellite in an inclined orbit
    Hao Wen Dongping Jin Haiyan Hu
    2008, 40(3):  375-380.  DOI: 10.6052/0459-1879-2008-3-2007-407
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    This paper presents a nonlinear optimal control scheme for the three-dimensional retrieval process of an electrodynamic tethered satellite system in an inclined orbit. The Legendre pseudospectral algorithm is used to acquire an optimal trajectory to guide the subsatellite into a final position close to the spaceship under mission-related constraints. The optimal control is discretized and solved with the nonlinear programming. The scheme is verified with the numerical simulation. The results shows that the control action is carried out by only adjusting the tensional and electrodynamic forces in the tether.
    Random vibration analysis of vehicle-track coupling systems using symplectic method
    Feng Lv Jiahao Lin Yahui Zhang
    2008, 40(3):  381-387.  DOI: 10.6052/0459-1879-2008-3-2007-428
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    The vertical coupling model of vehicle-track systems is set up in the case of the track as an infinite periodic structure. The random irregularity excitation of the rail is transformed into a deterministic harmonic excitation with the pseudo excitation method, and the frequency response of the track and the power spectrum density (PSD) of the system response are analyzed using the symplectic algorithm. In addition, there are only 26 DOFs in the computational model to have an efficient and accurate solution. The model is verified with the conventional FEM, and the influence of the vehicle velocity on the system vibration is investigated.
    Chaotic dynamics of liquid--filled flexible spacecraft in the large angle attitude maneuver
    Baozeng Yue
    2008, 40(3):  388-393.  DOI: 10.6052/0459-1879-2008-3-2007-388
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    In this paper, the chaotic dynamics of liquid-filled flexible spacecraft is investigated in the large angle attitude maneuver from minor axis to major axis with the influence of viscous damping of liquid fuel and the torsional vibration of flexible appendage. In addition, the coupled influence is focused in this paper. The dynamic equations are derived and transformed into a perturbation form. Melnikov's integral method is used to predict the chaotic attitude of the spacecraft, compared with the numerical results of the system. Furthermore, the effects on chaotic attitude of the spacecraft are investigated of spacecraft shape, the inertial momentum and the damping properties of liquid fuel, and the frequency of flexible appendage.
    Brief Report
    The influence of the turbulent statistical characteristics by cone effect in a supersonic boundary layer
    Ming Dong Jisheng Luo
    2008, 40(3):  394-401.  DOI: 10.6052/0459-1879-2008-3-2007-358
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    A spatial direct numerical simulation (DNS) was performed to study the turbulent statistical characteristics in the turbulent boundary layer on a blunt cone with an adiabatic wall at an oncoming Mach 2.5, zero angle of attack and the cone semi-angle of 5^{\circ} in this paper. The results were compared with the simulated cases of the supersonic turbulent boundary layer over a flat plate and the hypersonic turbulent boundary layer on a blunt cone at Mach 6, suggesting the influence of the turbulent statistics with the cone effect. The results showed that, the cone effect is significant on the mean temperature profile and the compressibility, but unimportant on the scaling velocity law, the distribution of Reynolds stress and the budget of turbulent kinetic energy.
    Viscoelastic fracture of a functionally graded material strip
    Weijie Li Baolin Wang Xinhong Zhang
    2008, 40(3):  402-406.  DOI: 10.6052/0459-1879-2008-3-2006-468
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    In this paper, the viscoelastic fracture of a functionally graded material strip with a crack normal to the gradient direction is studied. The linear elastic crack tip fields subjected to stress load and strain load are obtained with the finite element method. The effects of the crack location, crack length, material gradient index and the loading on the crack tip field are investigated. In addition, the stress intensity factors of the viscoelastic functionally graded strip are obtained with the correspondence principle for the viscoelastic solids.
    The constitutive model of fecrni alloy subjected to static and dynamic loading
    Xiaoxia Pan Yong Yu Yun Tan Yuze Chen
    2008, 40(3):  407-412.  DOI: 10.6052/0459-1879-2008-3-2006-543
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    In the present work, the flow stress of FeCrNi alloy is divided into two parts, athermal stress (long-range) and thermally activated stress (short-range), based on the dislocation dynamics of plastic deformation of metal material. Firstly, the yield stress, twins and dislocation configurations of the alloy are analyzed with the effect of temperature and strain rate. Hence, modified Johnson-Cook model is introduced to describe the athermal stress. Secondly, the distance between dislocation barriers \Delta l was found to mainly affect the thermally activated stress and the g(\gamma, \dot {\gamma}, T) function was educed and input in the Kocks model. Therefore the constitutive model of FeCrNi alloy was developed to describe the plastic response of FeCrNi alloy from low temperature to high temperature, and from static loading to dynamic loading.
    Coupling thermo-hydro-mechanical dynamic response of saturated soil subjected to internal excitation
    Rongyue Zheng Ganbin Liu Song Wu
    2008, 40(3):  413-420.  DOI: 10.6052/0459-1879-2008-3-2007-176
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    Dynamic response of saturated half-space foundation subject to an internal heat/mechanical excitation is investigated theoretically with Biot's wave theory and thermodynamic theory. The foundation is idealized to be uniform and poroelastic. The governing equations of the thermo-hydro-mechanical coupling are presented. The analytical solutions of temperature increment, stress, displacement and pore pressure are derived with the forward and the inverse Hankel transform. Numerical results are obtained to analyze the effect of the internal excitation frequency on the vertical displacement and the pore pressure. In addition, the cases of thermo-elastic and porous elastic models are compared in the numerical results.
    Transverse nonlinear nonplanar dynamics of an axially moving viscoelastic belt with integral constitutive law
    Yanqi Liu Wei Zhang Meijuan Gao Xiaoli Yang
    2008, 40(3):  421-432.  DOI: 10.6052/0459-1879-2008-3-2006-626
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    In this paper, the problem of the transverse nonlinear nonplanar oscillations of an axially moving viscoelastic belt with the integral constitutive law are investigated in the case of 1:1 internal resonance. The governing equations of this problem are firstly derived with the generalized Hamilton's principle to obtain the in-plane and out-of-plane transverse nonlinear oscillations of the axially moving viscoelastic belt neglecting the axially deformation. Perturbation analyses are carried out on these partial differential governing equations with the multiscale method and the Galerkin's approach to obtain four-dimensional averaged equations and to analyze the stabilities of the solution in the dynamic system. The simulation results show the periodic motion, the quasi-periodic motion and the chaotic motion in the transverse nonlinear nonplanar oscillations of the axially moving viscoelastic belt.