力学学报

Hillslope soil erosion process model for natural rainfall events

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

2008, 40(3) doi: 10.6052/0459-1879-2008-3-2006-329

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Test gas contamination induced by the interaction of shock/boundary layer in shock tunnels

Jinping Li, Heng Feng, Zonglin Jiang

A investigation on the interactions among thereflected-shock, boundary layer and contact region in the detonation-drivenshock tunnel was carried out by applying Navier-Stokes equations in amulticomponent system and the dispersion controlled dissipative (DCD)scheme. In addition, the physical mechanism of test gas contamination causedby the wall jet was analyzed, which dramatically reduces the experimentalduration in a shock tunnel. The numerical results indicated a simple andeffective method of installing to increase the experimental duration.

2008, 40(3): 289-296. doi: 10.6052/0459-1879-2008-3-2007-110

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the dynamics theory on the solidification of liquid droplets

Yongqiang Chen, Jianjun Xu

The present paper develops a simplifiedLiquid-Solid-Gas-Fog (LSGF) model in the solidification of dispersed liquiddroplets on the basis of mean field concept to obtain the uniformly validasymptotic solution of the initial value problem at small supercooling. Theresults show that the whole dynamics process can be divided into two stages,the transient transition stage and the solidification stage. In thetransient stage without phase transition, the initial temperaturedistribution prescribed in the system is quickly to be special spatial. Inthe solidification stage, there is the solid/liquid phase conversion processtill to the vanish of the liquid phase. In addition, the case of the liquidcopper droplets is simulated to obtain the duration and the temperaturedistribution of the solidification under various growth conditions.

2008, 40(3): 297-305. doi: 10.6052/0459-1879-2008-3-2007-496

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Hall effects in three-dimensional MHD generator

Haoyu Lv, Lee Chun-Hian, Haitao Dong, Gang Chen

A numerical procedure for analyzing the MHD flows in theMHD generator of the bypass scramjet engine was developed in the presentstudy by applying a five-equation model associated with non-ideal MHD flowsat low magnetic Reynolds number. In the numerical procedure, an entropycondition scheme was applied for solving the non-homogeneous Navier-Stokesequations and an SOR method for solving the elliptic equation governed theelectrical potential. The Hall effects on the MHD flow in the MHD generatorwere studied numerically. E-beams were shown as the ionizer to provide theeffective and stable conductivity in the MHD flows. The numerical resultsindicated that the Hall effects might make the distortions on the flow andelectric fields in the MHD generator to induce unstable secondary flow, andnon-uniform Joule heating. In addition, The performance parameters of theMHD generator were obtained numerically to reveal that the Hall effects maydeteriorate the performance of MHD generator.

2008, 40(3): 306-314. doi: 10.6052/0459-1879-2008-3-2007-293

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Characteristics of supercavitating flows around a hydrofoil

Xiangbin Li, Guoyu Wang, Mindi Zhang, Shuyan Liu

Supercavitation around a hydrofoil is studiedexperimentally to address the flowing characteristics. A high-speed videocamera is used to visualize the flow structures under different cavitationnumbers. The digital particle image velocimetry (DPIV) is employed tomeasure the velocity fields. The bubbles among the cavitating fields areused as the tracer particles to survey the velocity distribution inside thecavity and improve the tracking capability of the tracer particles. Theresults show that three distinct supercavitating flow regimes can beobserved with the decreasing cavitation numbers, in which the cavitationstructure varies with the distribution of the water-vapor mixing phase andvapor phase. A large velocity gradient exists around the interface betweenthe cavitation area and the free stream. In the cavitation area, thelower-velocity region moves from the foil's middle part to the downstreamwith the decrease of the cavitation number. The fluid velocity is low in thewater-vapor mixture region, while with the similar distribution in the freestream and the vapor region.

2008, 40(3): 315-322. doi: 10.6052/0459-1879-2008-3-2006-568

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Study on flow past a nano circular cylinders with different Reynolds numbers

Yinshi Li, Yaling He, Jie Sun, Wenquan Tao

The steady cross-flow past a circular cylinder in the lowReynolds numbers was investigated using non-equilibrium molecular dynamicssimulations with the Lennard--Jones potential. The results showed threebasic flow patterns in microscale, different from those in macroscale. Theflow 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, acavity in the downstream adjacent to the cylinder forms. Asymmetric vorticesappears as a transitional range when $12

2008, 40(3): 323-330. doi: 10.6052/0459-1879-2008-3-2007-205

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Wrinkling analysis of space inflatable membrane structures

Changguo Wang, Xingwen Du, Xiaodong He

In this paper, the wrinkling analysis of space inflatablemembrane structure was performed with the application of the contractionfactor, the stress condition and wrinkling characteristic. The parameter ofthe contraction factor was introduced to show the contraction in thedirection of texture, not the concept of the Poisson's ratio. The stressfield and deformation of the wrinkled inflatable membrane structure wereobtained. A deep discussion on the relationship between the Poisson's ratioand the contraction factor. Was carried out and the compatibility conditionof the deformation was redefined. Furthermore, the 2-D wrinkling analyticalmethod was extended into the case of the 3-D inflated structures. Theflexural wrinkling of an inflated cylinder tube was analyzed to obtain therelationship between the critical wrinkling and the structural or mechanicalparameters. The theoretical results were quantitatively verified and wellagreed with the experimental results.

2008, 40(3): 331-338. doi: 10.6052/0459-1879-2008-3-2006-374

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A sensitive precursor to catastrophic failure in heterogeneous brittle materials

Shengwang Hao, Ju Sun

In general, there are two failure modes in heterogeneousbrittle materials, the gradual failure and the catastrophic failure. Thepaper analyses the differences between the gradual failure and thecatastrophic failure based on statistical mesoscopic damage mechanics. Theresults show that the ratio of the released elastic energy to the damagedissipative energy can be served as a sensitive precursor of catastrophe.Furthermore the value of the non-dimensional ratio has a similar tendency tobe 1 with different responses in the two failure modes, that is, theresponse function R always decreases in the gradual mode, while increasesand tends to be infinite at the catastrophic point of the failure.

2008, 40(3): 339-344. doi: 10.6052/0459-1879-2008-3-2007-552

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The relationship between orthogonal static stresses in a plate and lamb wave velocity in an arbitrary direction

Jun Wang, Yanguan Wang

A general dispersion equation for Lamb waves in anarbitrary direction was derived in an isotropic hyperelastic plate subjectedto orthogonal static stresses with wavelet analysis. The relationship amongLamb wave velocity, orthogonal static stresses and frequency was analyzed inthe present study. In addition, we discussed the relationship between Lambwave velocity and uniaxial static stress with numerical method. The resultsprovides the theoretical basis for Lamb wave applied to the stressmeasurement in thin plate.

2008, 40(3): 345-354. doi: 10.6052/0459-1879-2008-3-2007-033

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Development on the visco-elastic constitutive model of cardiac muscle based on experiment

Hongrong Fang, Tao Tang, Xiangming Zhang, Zhuo Zhuang

Mechanical property data of canine cardiac muscle wereexperimentally obtained in the present study. In addition, finite elementsimulations were carried out for the uniaxial tension test and therelaxation test of canine cardiac muscle. The nonlinear elastic and viscousparameters of cardiac muscle are acquired to develop the nonlinearviscoelastic 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.

2008, 40(3): 355-363. doi: 10.6052/0459-1879-2008-3-2007-187

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Mechanical properties of plain high-strength high-performance concrete under biaxial compression after exposure to high temperatures

Zhenjun He, Yupu Song

This study aims to generate the mechanical responseof plain high-strength high-performance concrete (HSHPC) subjectedto 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}$C and600${^\circ}$C, using thetrue-triaxial loading system. The biaxial static compressivestrengths, strains at the peak stress and the stress-strain curves areobtained to analyze the influence of the temperature and the stress ratio.Failure modes of plain HSHPC specimens are observed. The experimentalresults show that the biaxial compressive strength of HSHPC is moresensitive to the stress ratio and the exposure treatment to hightemperatures than the uniaxial compressive strength. The Kupfer-Gerstlefailure criterion for plain HSHPC is developed with the parameters of thetemperature and stress ratio.

2008, 40(3): 364-374. doi: 10.6052/0459-1879-2008-3-2007-211

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Retrieval control of an electro-dynamic tethered satellite in an inclined orbit

Hao Wen, Dongping Jin, Haiyan Hu

This paper presents a nonlinear optimal control schemefor the three-dimensional retrieval process of an electrodynamic tetheredsatellite system in an inclined orbit. The Legendre pseudospectral algorithmis used to acquire an optimal trajectory to guide the subsatellite into afinal position close to the spaceship under mission-related constraints. Theoptimal control is discretized and solved with the nonlinear programming.The scheme is verified with the numerical simulation. The results shows thatthe control action is carried out by only adjusting the tensional andelectrodynamic forces in the tether.

2008, 40(3): 375-380. doi: 10.6052/0459-1879-2008-3-2007-407

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Random vibration analysis of vehicle-track coupling systems using symplectic method

Feng Lv, Jiahao Lin, Yahui Zhang

The vertical coupling model of vehicle-track systems isset up in the case of the track as an infinite periodic structure. Therandom irregularity excitation of the rail is transformed into adeterministic harmonic excitation with the pseudo excitation method, and thefrequency response of the track and the power spectrum density (PSD) of thesystem response are analyzed using the symplectic algorithm. In addition,there are only 26 DOFs in the computational model to have an efficient andaccurate solution. The model is verified with the conventional FEM, and theinfluence of the vehicle velocity on the system vibration is investigated.

2008, 40(3): 381-387. doi: 10.6052/0459-1879-2008-3-2007-428

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Chaotic dynamics of liquid--filled flexible spacecraft in the large angle attitude maneuver

Baozeng Yue

In this paper, the chaotic dynamics of liquid-filledflexible spacecraft is investigated in the large angle attitude maneuverfrom minor axis to major axis with the influence of viscous damping ofliquid fuel and the torsional vibration of flexible appendage. In addition,the coupled influence is focused in this paper. The dynamic equations arederived and transformed into a perturbation form. Melnikov's integral methodis used to predict the chaotic attitude of the spacecraft, compared with thenumerical results of the system. Furthermore, the effects on chaoticattitude of the spacecraft are investigated of spacecraft shape, theinertial momentum and the damping properties of liquid fuel, and thefrequency of flexible appendage.

2008, 40(3): 388-393. doi: 10.6052/0459-1879-2008-3-2007-388

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The influence of the turbulent statistical characteristics by cone effect in a supersonic boundary layer

Ming Dong, Jisheng Luo

A spatial direct numerical simulation (DNS) was performedto study the turbulent statistical characteristics in the turbulent boundarylayer on a blunt cone with an adiabatic wall at an oncoming Mach 2.5, zeroangle of attack and the cone semi-angle of 5^{\circ} in this paper. Theresults were compared with the simulated cases of the supersonic turbulent boundarylayer over a flat plate and the hypersonic turbulent boundary layer on ablunt cone at Mach 6, suggesting the influence of the turbulent statisticswith the cone effect. The results showed that, the cone effect issignificant on the mean temperature profile and the compressibility, butunimportant on the scaling velocity law, the distribution of Reynolds stressand the budget of turbulent kinetic energy.

2008, 40(3): 394-401. doi: 10.6052/0459-1879-2008-3-2007-358

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Viscoelastic fracture of a functionally graded material strip

Weijie Li, Baolin Wang, Xinhong Zhang

In this paper, the viscoelastic fracture of a functionallygraded material strip with a crack normal to the gradient direction isstudied. The linear elastic crack tip fields subjected to stress load andstrain load are obtained with the finite element method. The effects of thecrack location, crack length, material gradient index and the loading on thecrack tip field are investigated. In addition, the stress intensity factorsof the viscoelastic functionally graded strip are obtained with thecorrespondence principle for the viscoelastic solids.

2008, 40(3): 402-406. doi: 10.6052/0459-1879-2008-3-2006-468

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The constitutive model of fecrni alloy subjected to static and dynamic loading

Xiaoxia Pan, Yong Yu, Yun Tan, Yuze Chen

In the present work, the flow stress of FeCrNi alloy is dividedinto two parts, athermal stress (long-range) and thermally activated stress(short-range), based on the dislocation dynamics of plastic deformation ofmetal material. Firstly, the yield stress, twins and dislocationconfigurations of the alloy are analyzed with the effect of temperature andstrain rate. Hence, modified Johnson-Cook model is introduced to describethe athermal stress. Secondly, the distance between dislocation barriers\Delta l was found to mainly affect the thermally activated stress andthe g(\gamma, \dot {\gamma}, T) function was educed andinput in the Kocks model. Therefore theconstitutive model of FeCrNi alloy was developed to describe the plasticresponse of FeCrNi alloy from low temperature to high temperature, andfrom static loading to dynamic loading.

2008, 40(3): 407-412. doi: 10.6052/0459-1879-2008-3-2006-543

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Coupling thermo-hydro-mechanical dynamic response of saturated soil subjected to internal excitation

Rongyue Zheng, Ganbin Liu, Song Wu

Dynamic response of saturated half-space foundationsubject to an internal heat/mechanical excitation is investigatedtheoretically with Biot's wave theory and thermodynamic theory. Thefoundation is idealized to be uniform and poroelastic. The governingequations of the thermo-hydro-mechanical coupling are presented. Theanalytical solutions of temperature increment, stress, displacement and porepressure are derived with the forward and the inverse Hankel transform.Numerical results are obtained to analyze the effect of the internalexcitation frequency on the vertical displacement and the pore pressure. Inaddition, the cases of thermo-elastic and porous elastic models are comparedin the numerical results.

2008, 40(3): 413-420. doi: 10.6052/0459-1879-2008-3-2007-176

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Transverse nonlinear nonplanar dynamics of an axially moving viscoelastic belt with integral constitutive law

Yanqi Liu, Wei Zhang, Meijuan Gao, Xiaoli Yang

In this paper, the problem of the transverse nonlinearnonplanar oscillations of an axially moving viscoelastic belt with theintegral constitutive law are investigated in the case of 1:1 internalresonance. The governing equations of this problem are firstly derived withthe generalized Hamilton's principle to obtain the in-plane and out-of-planetransverse nonlinear oscillations of the axially moving viscoelastic beltneglecting the axially deformation. Perturbation analyses are carried out onthese partial differential governing equations with the multiscale methodand the Galerkin's approach to obtain four-dimensional averaged equationsand to analyze the stabilities of the solution in the dynamic system. Thesimulation results show the periodic motion, the quasi-periodic motion andthe chaotic motion in the transverse nonlinear nonplanar oscillations of theaxially moving viscoelastic belt.

2008, 40(3): 421-432. doi: 10.6052/0459-1879-2008-3-2006-626

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