力学学报

STUDY ON THE FORMATION MECHANISMS OF UNSTEADY AERODYNAMIC CHARACTERISTICS OF MORPHING FLIGHT VEHICLE IN SWEEP-VARYING PROCESS

Chen Qian, Bai Peng, Li Feng

Time-dependent aerodynamic forces and moments of morphing aircraft during sweep-varying process are important to flight safety, and hence need thorough investigations. This paper conducted a wind tunnel experiment of morphing aircraft and analyzed the aerodynamic characteristics. The results demonstrate the dynamic hysteresis caused by sweep-varying, and various factors that affect the magnitude and director of hysteresis loop. Based on these results and some important concepts in mechanics, three physical effects, i.e., flow-field hysteresis effect, additional motion effect and wall implication effect, were proposed in order to interpret the formation mechanisms of the unsteady aerodynamic characteristics of morphing aircraft. This investigation about mechanisms can be used to further study on modeling of aerodynamic characteristics.

2013, 45(3): 307-313. doi: 10.6052/0459-1879-12-302

PDF

THE STUDY BASED ON THE CONTINUUM MODEL FOR THE MICRO-SCALE POISEUILLE FLOW

Song Chengqian, Yin Xieyuan, Qin Fenghua

In this paper, the planar microchannel force-driven Poiseuille flow was analyzed by using the gas kinetic theory and the macroscopic continuous flow theory, respectively. In the kinetic theory, the direct simulation Monte Carlo (DSMC) method was used where the body force was a substitute for the pressure gradient in order to ignore the length effect of the channel. In the continuous flow theory, the Burnett and super-Burnett constitutive relations were adopted and nonlinear ordinary differential equations of higher-orders were obtained by the hypothesis of parallel flow. Then, the equations were solved by Runge-Kutta method with the necessary boundary conditions. It was shown that the pressure distribution predicted by the high order continuous model could agree very well with that by DSMC even when the flow was in the transition region. And deviation of the velocity would exist near the wall when the Knudsen number is larger than 0.2. The temperature dip can not be obtained by Burnett model what will revert to the Navier-Stokes model for temperature distribution. The super-Burnett model can capture the temperature dip, similar to the DSMC result, while the temperature profile near the wall is quite different from the DSMC result. The non-equilibrium effect near the wall such as Knudsen layer can not be described entirely by continuous model even with high order constitutive relations and this confines the extension of the continuous model.

2013, 45(3): 314-322. doi: 10.6052/0459-1879-12-294

PDF

STUDY ON THE STABILITY OF LIQUID JET IN COAXIAL SWIRLING COMPRESSIBLE FLOW UNDER SUPERCAVITATION

Lü Ming, Ning Zhi, Yan Kai, Fu Juan, Song Yunchao, Sun Chunhua

In this paper, a mathematical model is presented for studying on the stability of compressible liquid jet in a coaxial swirling compressible airstream. The mathematical model and its solving method are verified by the data in literature, and the influences of compressibility, swirling gas and supercavitation on the stability of liquid jet are investigated, respectively. The results show that compressibility plays an important role in the instability of liquid jet. The range of wave numbers, the drop distributions and the drop diameters are changed due to compressibility. The effects of swirling gas on the stability of liquid jet are different in various disturbance modes. However, gas swirling has little impact on drop diameters. It is also found that the liquid jet becomes more unstable due to the greater supercavitating condition. Supercavitation with a small void fraction gets the greater wave numbers and the smaller drop diameters, while it draws different conclusion when void fraction reaches a certain value.

2013, 45(3): 323-330. doi: 10.6052/0459-1879-12-223

PDF

EFFECTS OF ASPECT RATIO OF RECTANGULAR CHANNEL ON CHARACTERISTICS OF SINGLE-PHASE LAMINAR FLOW

Xing Dianchuan, Yan Changqi, Wang Chang, Sun Licheng

The frictional resistances for wide side and narrow side of rectangular channels with different aspect ratios are compared, by analyzing the wall shear stress. The results show that the frictional resistance of the wide side increases sharply as the aspect ratio decrease, of which shows the reversed trend in a smaller range for the narrow side. Therefore the total frictional resistance increases with the decreasing of the aspect ratio. The frictional resistance proportion for wide side out of the total decreases as the aspect ratio increases, more slowly for the larger aspect ratio. The aspect ratio has remarkable influence on both the magnitude and the distribution type of shear stress for wide side, whereas, it has limited influence on shear stress for narrow side. Additionally, the transition Reynolds number of laminar to turbulent flow is calculated by energy gradient method and a polynomial correlation is achieved. The predicted results show good agreement with the experimental data.

2013, 45(3): 331-336. doi: 10.6052/0459-1879-12-246

PDF

DISTURBED PRESSURE DISTRIBUTION ALONG SLIGHTLY CURVED BANKLINE BASED ON SMALL-DISTURBANCE THEORY

Lin Junqiang, Yan Zhongmin, Xia Jihong

In order to reveal the discipline and the main influence factor of disturbed pressure distribution along sinuous bankline, the small disturbance theory was used to linearize the 2D shallow water equations and the boundary conditions. Analytic expressions of disturbed pressure along sinusoidal curved bankline had been derived. A sensitivity analysis of influence factors was also presented. The pressure expressions and sensitivity analysis show that the disturbed pressure along the slightly curved bankline follows sinusoidal distribution. The crest and trough values of disturbed pressure appear at the maximum curvature locations of concave and convex bank, respectively. The bank amplitude-to-wavelength ratio a/λ is found to be the main factor of pressure variation in subcritical flow. The derived results can be used to estimate the boundary condition of stream-subsurface exchange in riparian zones, which is helpful to the further study on lateral hyporheic exchange and hydrodynamics in riparian areas.

2013, 45(3): 337-342. doi: 10.6052/0459-1879-12-173

PDF

THE TEST STUDY ON THE ATTENUATION MOTION CHARACTERISTICS AND IRREGULAR WAVES RESPONSE OF THE FLOATING TIDAL POWER GENERATION DEVICE

Ma Yong, Zhang Liang, You Shizhou

In order to study the attenuation motion characteristics and irregular wave response of the floating tidal power generation device with vertical-axis tidal turbine, the experimental model is designed and mooring test platform is built to conduct the free attenuation test, mooring attenuation test and irregular waves response test based on the mooring trial carried out in ship model test towing tank. The model's shaking attenuation characteristics is measured in attenuation test and also the tensile response of mooring line and shaking response of the combined model are measured in irregular wave response test. Finally the attenuation motion characteristics of the floating tidal power device is acquired and the tensile response of mooring line 1 and shaking response of combined model under the four-grade oceanic condition when the flow velocity is 0.6m/s are achieved which can provide the reference to theoretical research and engineering application of the floating tidal power device with vertical-axis tidal turbine.

2013, 45(3): 343-348. doi: 10.6052/0459-1879-12-337

PDF

VIBROACOUSTIC PERFORMANCE OF SIMPLY SUPPORTED HONEYCOMB SANDWICH PANELS

Ren Shuwei, Xin Fengxian, Lu Tianjian

Honeycomb sandwiches used as hulls and floor panels of high-speed train and other transportation vehicles require not only excellent mechanical stiffness/strength but also good sound insulation performance. The vibroacoustic performance of a finite rectangular honeycomb sandwich panel with simply supported boundary conditions is investigated analytically. The vibration governing equation of the structure is established by applying an equivalent method for the honeycomb core and Reissner's theory for sandwich panels. With sound pressure introduced into the vibroacoustic governing equation in the form of double Fourier series, the resultant equations are solved numerically in conjunction with fluid-structure coupling condition. Numerical simulation results with the method of finite elements are employed to validate the analytical model, with excellent good agreement achieved. The developed model is used to investigate the influence of several key system parameters on sound transmission of the structure, including the core thickness, honeycomb wall thickness, in-plane panel dimensions and sound incidence angles. The model presented here holds great practical potential for the optimization design of honeycomb sandwich structures.

2013, 45(3): 349-358. doi: 10.6052/0459-1879-12-280

PDF

FINITE ELEMENT METHOD FOR CRACK PROBLEMS IN VISCOELASTIC FUNCTIONALLY GRADED MATERIALS

Peng Fan, Ma Qingzhen, Dai Hongliang

A finite element approach is developed to analyze the crack problems in viscoelastic functionally materials with arbitrary volume fraction distribution of constituents. By Laplace transform, the boundary problems are solved in phase domain based on graded element considering the heterogeneous of material and singular element describing the singularity of stresses near crack tips. The virtual crack closure technique modified by Rybicki et al. is applied to evaluate strain energy release rate, and the stress intensity factor is determined by means of nodal stress and strain energy release rate, respectively. The relationships of fracture parameters in time domain and phase domain are formulated, and the corresponding solutions in time domain are obtained by numerical Laplace inversion. The crack problem in viscoelastic functionally graded plate with edge crack parallel to graded direction is investigated. Two cases are involved in the analysis. The first one is for special functionally graded material with relaxation modulus expressed by the product of spatial variable function and time function. The second one is for general functionally graded materials of arbitrary volume fraction distribution of constituents. The validity of the finite element method proposed in the paper is verified in the first case on the basis of the elastic-viscoelastic correspondence principle. For the second case, Mori-Tanaka method is used to predict the effective relaxation modulus of functionally graded materials in phase domain. The results in creep loading condition show that the strain energy release rate increases with time elapsed, and the variation range depends on the volume content of viscoelastic constituent. The stress intensity factor may change over time due to the stress redistribution around crack tip originating from the heterogeneous viscoelasic property of graded material, and the time-dependent variation is influenced by the distribution pattern of volume fraction.

2013, 45(3): 359-366. doi: 10.6052/0459-1879-12-264

PDF

A PREDICTION METHOD ON HIGH-CYCLE FATIGUE PARAMETERS BASED ON DISSIPATED ENERGY COMPUTATION

Li Yuan, Han Xu, Liu Jie, Jiang Chao

A heat conduction equation under high-cycle fatigue loadings was established using sheet assumption within thermodynamic framework. Dissipated energy per cycle, correlated with fatigue damage, could be deduced from temperature field data of specimen and real-time load signal. Then, taking 316L stainless steel for example, the dissipation energy per cycle variations were in-situ monitored during each high-cycle fatigue test under different stress levels. Dissipated energy versus fatigue lifetime curve shows the same pattern as the traditional stress versus fatigue lifetime curve. A new energy method was developed to predict high-cycle fatigue limit. The high-cycle fatigue limit determined by dissipated energy measurement was close to the experimental fatigue limit.

2013, 45(3): 367-374. doi: 10.6052/0459-1879-12-300

PDF

AN EXPERIMENTAL STUDY ON THE EFFECT OF INTER-PARTICLE FRICTION ON SHEAR BEHAVIOR OF GRANULAR MATERIALS

Dai Beibing, Yang Juny, Zhou Cuiying

This paper describes an investigation into the effect of inter-particle friction on shear behavior of granular materials, by performing a series of direct shear tests on an analogous soil - glass bead. In this test study, four types of inter-particle friction conditions are concerned, including dry state, water-lubricated state, flooded state and oil-lubricated state. An analysis of the test results reveals that oil lubrication is able to significantly decrease dilatancy and shear strength of granular specimens, whereas the means of water lubrication and complete submergence in water do not exert a notable effect. Based on test results, a stress-dilatancy equation is proposed that is able to properly take into account the effect of inter-particle friction on the dilatancy of granular materials. The effect of inter-particle sliding friction angle on critical state friction angle is preliminarily examined from a perspective of microscopic particle motions, namely, particle sliding and rolling.

2013, 45(3): 375-383. doi: 10.6052/0459-1879-12-250

PDF

STUDY OF TIGHT SANDSTONE PERMEABILITY FROM LATTICE BOLTZMANN & DIGITAL ROCK MODEL

Zhu Bojing, Shi Yaolin

Due to the experimental technology condition, to measure the permeability of the porous rock is still a changeling problem, especially for low or ultralow permeability porous rock. X-ray computed tomography (CT) technology, which can conveniently be used to obtain high-resolution internal structure data of the rock, is more and more widely used to predict and explore the permeability physical properties of the low or ultralow porous rock. How to determine the CT cross-section resolution is one of the key issues in the predict process, even this approach has some incomparable advantages of experimental methods, with high precision, convenient, and the field measurement. In this work, the tight sandstone sample from the Ordos Basin Triassic formation is selected and different tomography resolution data are obtained from Kochi Institute for Core Sample Research (10μm), National Synchrotron Radiation Laboratory of Chinese Academy of Sciences (5μm, 2μm) and National Institute of Metrology of China (2μm), respectively. Then, based on the D3Q27 lattice Boltzmann method & virtual digital physical technology, the permeability under coupled confining pressure (0～200MPa), pore pressure (0～65MPa) and temperature (25℃～180℃) is measured. The results show that when the tomography resolution is located at 2μ, the results are consisted with the experimental results obtained from Inc AUTOLAB 2000C rock system. The permeability anisotropy of tight sandstone under ultra-high temperature and pressure (0℃～400℃, 0～1.4GPa) is explored and this will be helpful to understand the strength decrease of asthenosphere and interaction between lithosphere and asthenosphere.

2013, 45(3): 384-394. doi: 10.6052/0459-1879-12-273

PDF

EFFECTS OF SQUIRT-FLOW IN CRACKS ON DRAINED BULK MODULUS OF POROUS MEDIA

Song Yongjia, Hu Hengshan

Sedimentary rocks are typical porous media which usually contain both cracks and pores. Liquid in rocks will be squeezed out of flat cracks and then flow into spherical pores when rocks are under pressure because cracks are much softer than pores. This kind of flow between cracks and pores is squirt-flow which usually induces elastic modulus dispersion and wave attenuation. This paper studies the effects of squirt-flow as well as the liquid compressibility on the deformation of pore space and derives the expression of drained bulk modulus under dynamic loads. There exists a crack compliance in the expression of drained bulk modulus. The crack compliance contains both the contribution of squirt-flow which is caused by pressure difference between cracks and pores and the contribution of the compressibility of the liquid in cracks. The additional compliance brings about dispersion on drained bulk modulus. The real part of drained bulk modulus increases as frequency increases which means that at high frequency rock becomes stiffer, the imaginary part of drained bulk modulus represents the energy loss in the squirt-flow. Crack density mainly decides the modulus dispersion amplitude and the squirt-flow intensity. The crack aspect ratio mainly decides the characteristic frequency of squirt-flow. The expression of drained modulus in this paper reduces to Biot expression when crack density equals zero.

2013, 45(3): 395-405. doi: 10.6052/0459-1879-12-230

PDF

GYROSCOPIC PRECESSION AND FORCED PRECESSION ORBIT

Cao Jing, Yuan Jianping, Luo Jianjun

The analogous precession phenomena of gyroscope and orbital plane are based on the dynamical similarity. In present paper a special kind of forced precession orbit is proposed through the comparison of dynamical models of gyroscope and orbital plane. When the initial orbit is a circular orbit, the forced precession orbit can be realized by the action of a constant normal control force. The characters of forced precession orbital motion are discussed using the mathematical model expressed by quaternion, and the analytical solutions are obtained. It is shown that the forced precession orbit and the initial orbit are laying on the same spherical surface, and they are tangent each other at the initial position. The angular velocity of the forced precession orbit is the summation of precession speed and the angular velocity of the initial orbit. The new orbit is a non-Keplerian displaced orbit, which has a potential perspective of applications in Earth observation, planetary science, observational astronomy, telecommunications and geo-engineering. The analysis from the view point of forced precession provides a new way to realize the displaced orbit.

2013, 45(3): 406-411. doi: 10.6052/0459-1879-12-375

PDF

AN ANALYTICAL STUDY OF GRAVITY ASSIST IN THREE DIMENSIONS

Jia Jianhua, Wang Qi

New analytical equations are derived for the three-dimensional gravity assist based on the patched conics model, including the variations in velocity, angular momentum, energy and inclination of the spacecraft due to the gravity assist. The equations developed here are verified by numerical integrations, using the circular restricted three-body problem, showing a good agreement better than 0.01. The results predicted by these analytical equations and the results computed by the numerical method differ by less than 0.7% under most conditions. This is a good indication that the analytical equations are good approximations and can be used for preliminary mission design. The influence of the parameters on the orbit of spacecraft is discussed based on the simplified equations which are the approximations of the above equations.

2013, 45(3): 412-420. doi: 10.6052/0459-1879-12-267

PDF

FIRST PASSAGE PROBABILITIES OF STRUCTURAL DYNAMICS SYSTEM BASED ON DOMAIN DECOMPOSITION

Ren Limei, Xu Wei

The first passage problems of linear and nonlinear dynamical systems excited by Gauss white noise are considered. For linear dynamical system, the failure domain can be described as a union of mutually exclusive events, and every event is completely described by a local design point. The paper uses standard Gaussian distribution instead of chi-square distribution to estimate the parameter of first passage probability. For nonlinear dynamical system, the equivalent linear system is carried out based on the out-crossing theory. The linearization principle is that nonlinear and linear systems have the same up-crossing rate for a specified threshold. Finally the paper gives two examples. The results show that the method of the paper suggested is correct and effective by comparing with the Monte Carlo method.

2013, 45(3): 421-425. doi: 10.6052/0459-1879-12-355

PDF

CONTACT ANALYSIS OF DEEP GROOVE BALL BEARING JOINT IN MULTIBODY SYSTEMS

Qi Zhaohui, Wang Gang, Li Tan

Detecting locations of contacts is the most important issue for contact analysis of a joint in multibody dynamics, which traditionally requires the details of the relative motion of bodies in the joint as well as the solution of the resulted complementarity problem. However, clearances in a joint may be so tiny that it is hard to distinguish the relative displacements from computational errors. In this case, the contact analysis becomes extremely difficult due to the serious numerical ill-conditioned characteristics of traditional methods. In this paper, with the consideration of the structural details of deep groove ball bearing, we found the kinematic conditions for a ball to be simultaneously in contact with the inner and outer races, as well as the characteristic of contact forces on the ball that is carrying a load. Consequently, we present a methodology, in which the forces and locations of contacts can be obtained by means of joint reaction forces instead of relative motions. By the proposed method, the difficulties arising from microscopic relative motions and nonlinear complementarity problems are avoided, and the numerical efficiency is improved. Numerical examples prove the validity of the method.

2013, 45(3): 426-433. doi: 10.6052/0459-1879-12-320

PDF

STUDY ON ATTITUDE DISTURBANCE AND CONTROL OF MOTHER SATELLITE DURING SPACE NET PROJECTING

Gao Zhijie, Sun Fuchun, Min Haibo, Wang Shixing

Space net capturing is a novel technique for spacecraft capturing. In this paper, the disturbance imposed on the mother satellite, and the induced attitude control problem of the satellite, are investigated. Attention is focused on the dynamic process of mass ejection. The main factors affecting the performance of the net are analyzed and the model of the disturbance torque is developed. A sliding mode controller is developed to stabilize the attitude of the satellite and rigid mathematical proof is provided. Numerical simulation is conducted which demonstrates the effectiveness of the proposed algorithm.

2013, 45(3): 434-441. doi: 10.6052/0459-1879-12-249

PDF

IMPROVEMENT AND ASSESSMENT OF THE SST EQUATION BASED ON KARMAN SCALE AND FILETER METHOD

Zhang Yang, Bai Junqiang, Hua Jun, Lu Jun

A modified filter method of SST turbulence model based on Karman length scale correction has been proposed in this paper. With application of the sub-grid model in LES theory, a new DES method has been established, which could alleviate the restriction to flow fluctuation by the time averaging in RANS solver so that the multi-scale effect in separated flow could be simulated. Besides, the filter factor has been modified with the Karman scale to reduce the dissipation of Reynolds stress which would occur in the original DES cased by grid refinement。In the numerical study case of flat plate boundary layer, the velocity profile within the boundary layer would match well the result by RANS, compared to the low robustness and poor capability inside boundary layer of DES method with grid refinement, which shows that the Karman scale has guaranteed that the flow inside the boundary layer would be solved by RANS instead of LES. HGR-01 airfoil test case proves that BY-SST method can avoid the grid induced separation more robust than that of DES method.

2013, 45(3): 442-446. doi: 10.6052/0459-1879-12-240

PDF

TIME DISCONTINUOUS GALERKIN FINITE ELEMENT METHOD FOR GENERALIZED THERMO-ELASTIC WAVE OF NON-FOURIER EFFECTS

Guo Pan, Wu Wenhua, Wu Zhigang

In the paper, we present a modified time discontinuous Galerkin finite element method (DGFEM) for the solution of generalized thermo-elastic coupled problems based on well-known non-Fourier Lord-Shulman theory. The general temperature and displacement fields with their time derivatives are interpolated in time domain, respectively. In order to filter out the spurious wave-front oscillations, an artificial damping scheme is implementation in the final finite element formula. Numerical results show that the present modified DGFEM proposes the good abilities and provides much more accurate solutions for generalized thermo-elastic coupled behavior. It can effectively capture the discontinuities at the wave front and filter out the effects of spurious numerical oscillation induced by thermal shock.

2013, 45(3): 447-450. doi: 10.6052/0459-1879-12-217

PDF

AN ANISOTROPIC HYPERELASTIC CONSTITTUTIVE MODEL WITH SHEAR INTERACTION FOR CORD-RUBBER TIRE COMPOSITES

Guo Guodong, Peng Xiongqiy, Zhao Ning

A new anisotropic hyperelastic constitutive model for tire cord-rubber composites was proposed. The strain energy of the cord/rubber composite material was decomposed nominally into four parts, representing the strain energy of rubber, cords, shear and normal interactions between rubber and cords, respectively. A simple approach for fitting parameters in the model was given. Experimental data from the literature was used to obtain the material parameters in the constitutive model. The mechanical behavior of the composite was predicted and compared with experimental data for model validation. Very good agreement was obtained. The proposed model provides a foundation for finite element analysis of the tire in the future.

2013, 45(3): 451-455. doi: 10.6052/0459-1879-12-212

PDF

RESEARCH ON THE METHOD FOR RELIABILITY ANALYSIS OF STRUCTURAL SYSTEMS BASED ON THE DIMENSIONAL-REDUCTION INTEGRATION

Huang Xianzhen, Zhang Yimin, Wu Maochang, Li He

There are usually several failure models in a complex structural system. The conventional model for system analysis is built under the condition that all failure models are independent with each other. However, in engineering practice, failure models in a system are mostly dependent due to the fact that the elements of a structural system are closely interrelated. System reliability analysis and evaluation simply conducted under the condition that all failure models are independent with each other often result in excessive errors or even wrong conclusion. This paper proposes a method for reliability analysis of engineering structural systems with dependent failure models. The dimensional reduction method and Gauss-Hermite quadrature are applied to compute the statistic moments of the limit state functions of structural systems with random parameters. The first four cumulants of the limit state functions are used to approximate cumulant generating functions. The probability density function and cumulative distribution function of the limit state functions of the structural systems are fitted through saddlepoint approximation. And then the reliability (or failure probability) of the structural system is obtained. Finally, the practicality and efficiency of the proposed method are demonstrated by a numerical example.

2013, 45(3): 456-460. doi: 10.6052/0459-1879-12-326

PDF

HOMOCLINIC ORBIT OF STRONGLY NONLINEAR AUTONOMOUS OSCILLATOR VIA GENERALIZED PADÉ APPROXIMATION METHOD

Li Zhenbo, Tang Jiashi, Cai Ping

The generalized Padé approximate definition is proposed based on classical definition of Padé approximation. By utilizing the hyperbolic function, a new form of generalized Padé approximation is constructed for determining the homoclinic orbit of strongly nonlinear autonomous oscillator. The Taylor expansion of generalized Padé approximation in this paper is simpler than existing ones, which means that the proposed method has less complexity in calculation. The precision of the solutions is high when the nonlinear parameters are large. The proposed method is not restricted to solve some certain systems. It can be utilized in many kinds of systems, which means that the proposed method is generally applicable. So the investigation in generalized Padé approximation is meaningful.

2013, 45(3): 461-464. doi: 10.6052/0459-1879-12-277

PDF

THE INTRODUCTION OF APPLICATION PROJECTS ON MECHANICS IN 2013

Zhan Shige, Zhang Panfeng, Wang Lifeng, Xu Xianghong

The paper introduced the applications for NSFC programs on mechanics in 2013. The statistics of application projects for General Programs, Young Scientists Fund, Fund for Less Developed Regions, Key Programs, Excellent Young Scientists Fund, National Science Fund for Distinguished Young Scholars and Joint Research Fund for Overseas Chinese Scholars and Scholars in Hong Kong and Macao are presented and compared with applications in 2012.

2013, 45(3): 465-466. doi: 10.6052/0459-1879-13-134

PDF

2013 Vol. 45, No. 3

NoticeMORE+

Exquisite ArticlesMORE+

Download Center

Author Center