2013 Vol. 34, No. 9

Display Method:
Nonlinear Vibration of Vehicle-Pavement Coupled System Based on High-Order Galerkin Truncation
YANG Yan, DING Hu, CHEN Li-qun
2013, 34(9): 881-890. doi: 10.3879/j.issn.1000-0887.2013.09.001
Abstract(1215) PDF(1372)
The moving vehicle was modeled as a two DOF spring-mass-damper system. The pavement structure was modeled as an elastic beam on a nonlinear viscoelastic foundation. The nonlinear foundation and the road surface roughness were respectively assumed to be cubic and a harmonic function. The nonlinear partial differential governing equations of the vehicle-pavement coupled vibration were developed. The dynamic response of the coupled system was solved with the high-order Galerkin truncation method in conjunction with numerical method. The effects of different truncation orders on the dynamical responses of the vehicle-pavement nonlinear vibration were discussed, and the convergence of the Galerkin truncation to investigate the vehicle-pavement coupled vibration were determined for the first time. The study shows that the numerical investigation into dynamical response of the asphalt pavement on soft soil foundation needs over 150 terms.The influences of system parameters on the dynamical response were numerically studied via the high-order convergent Galerkin truncation method.
Research on Lateral Stability,Bifurcation and Chaotic Motions of Heavy Vehicle With Road Direction Disturbance
LI Shao-hua, WU Jin-yi, HU Bin
2013, 34(9): 891-899. doi: 10.3879/j.issn.1000-0887.2013.09.002
Abstract(1333) PDF(1067)
A closed-loop driver-vehicle-road model with two degrees of freedom (DOF) for a three-axle heavy vehicle was set up. With the influence of the road directional disturbance and driver control considered,the vehicle ordinary differential equations of motion were established. The influences of system parameters including wheelbase,preview distance,loading,time delay of driver control and tire lateral stiffness on steering stability were studied by numerical simulations,based on the Hopf bifurcation theory. The range of numerical stability of the steering system was also determined. Moreover,the nonlinear dynamics of this closed-loop driver-vehicle-road system at different vehicle running speeds were investigated by numerical methods,such as bifurcation,time history curve,phase trajectory,power spectrum,Poincaré section and Lyapunov exponent. It is shown that periodic,quasi-periodic and chaotic motions may take place with the increase of running speed,and the lateral stability of the vehicle mainly depends on the vehicle and driver model parameters.
Nonlinear Analysis on a 2D WIG Operating Near Water Waves
2013, 34(9): 900-907. doi: 10.3879/j.issn.1000-0887.2013.09.003
Abstract(1269) PDF(1008)
A nonlinear analysis on a 2D foil subject to wing-in-ground effect (WIG) operating above water waves was made. Through the derivation of the Green’s function for 2D singularities moving above regular water waves, the 2D lifting problem for a foil above water waves was addressed using the discrete vortex method. The results of non-dimensional lift coefficient were presented with the variation of different geometry and water wave parameters. The existing steady data are utilized to validate the present study.
Analysis of Water-Hammer Wave Speed and Friction Loss in Annular Space
XI Bin, HAN Hong-sheng, LIU Yang, ZHOU Ji-ren
2013, 34(9): 908-916. doi: 10.3879/j.issn.1000-0887.2013.09.004
Abstract(1394) PDF(861)
In order to study the phenomenon and regular movementpattern of liquid flow in annular space in projects such as oil extraction and drilling,the water hammer problem of liquid flow in annular space,which was rarely addressed at the moment,was discussed. According to the structure characteristics of annular space and the motion characteristics of fluid,the calculating formula of water-hammer wave speed was deduced in annular space.The calculating method of friction drag and its effect on the wave speed equations were discussed. The obtained water-hammer wave speed equations could provide reference for the further research of mobility pattern and characteristics of liquid flow in annular space.
New Approach to the Correlation Measurement for Subsystems in a Complex Giant System
LIN Yong-xin, CHEN Yu-shu, WANG Dan, CAO Qing-jie
2013, 34(9): 917-928. doi: 10.3879/j.issn.1000-0887.2013.09.005
Abstract(1039) PDF(898)
A nonlinear mutual prediction approach was presented to investigate the correlations and coupling strengths of nonlinear dependence among the subsystems in an open complex giant system, which behaved with complicated nonlinear dynamical characteristics. The time-varying discriminant values of mutual dependence obtained with the proposed method could be used to predict the correlations of the subsystems in a giant system based upon phase space reconstruction by using the observed small data and micro signal. Moreover, the obtained mechanism of interaction between the subsystems provides a nonlinear mutual prediction measurement, which is suitable for the analysis of financial crisis analytically.
Global Exponential Periodicity of Discrete-Time Complex-Valued Neural Networks With Time-Delays
HU Jin, SONG Qian-kun
2013, 34(9): 929-940. doi: 10.3879/j.issn.1000-0887.2013.09.006
Abstract(1190) PDF(942)
Since the last decade, complex-valued neural networks have been rapidly developed and applied in various research areas, but few research has been done on the periodicity on discrete-time complex-valued neural networks.The periodicity of discrete-time complex-valued neural networks with time-delays was investigated.With the discretization technique, the discrete-time analogue of the continuous-time system with periodic input was formulated, and a sufficient condition for checking the global exponential periodicity of the considered neural networks was obtained. Numeric simulation verifieds validity of the analysis.
New Criteria for Oscillation of Third Order Nonlinear Delay Differential Equations
LUO Li-ping, YU Yuan-hong, ZENG Yun-hui
2013, 34(9): 941-947. doi: 10.3879/j.issn.1000-0887.2013.09.007
Abstract(1158) PDF(1009)
Oscillatory problems of a class of third order nonlinear delay differential equations were studied. With the techniques of operator and integral, the determinant conditions in which such equations had not A-type solution (or B-type solution) were given. Further, several new sufficient conditions for oscillation of such equations were obtained via suitable comparison theorems. Obtained results generalize and improve some known results of the latest literature and fully reflect the influence action of delay in equation oscillation. The main results are illustrated by some examples.
Applications of Landweber Interation Regularization Method in Dynamic Load Identification
CHANG Xiao-tong, YAN Yun-ju, LIU Liu
2013, 34(9): 948-955. doi: 10.3879/j.issn.1000-0887.2013.09.008
Abstract(1236) PDF(1177)
The inverse problem of force identification was always ill-posed due to the inverse process of structural matrix and measurement noise in practical engineering and the ordinary least square method usually obtained the meaningless solution, which was called the ill-posed problem of the inverse problem. The Landweber iteration regularization method was proposed to overcome these problems. The load can be expressed as a series of kernels of impulse function in time domain and the total response of the system can be obtained with the product of the convolution integral of the kernel responses and the load. The load were identified on a bridge model. The simulation results show that the identification method proposed is effective and it can meet the engineering requirements of stable approximate solution.
Direct Numerical Simulation of the Wall-Bounded Turbulent Flow by Lattice Boltzmann Method Based on Multi-GPU
XU Ding, CHEN Gang, WANG Xian, LI Yue-ming
2013, 34(9): 956-964. doi: 10.3879/j.issn.1000-0887.2013.09.009
Abstract(1402) PDF(1383)
The wallbounded turbulent flow was simulated directly (DNS) by lattice Boltzmann method (LBM) through multi-GPU parallel computing. The Data-parallel SIMT (single-instruction multiple-thread) characteristic of GPU matched the parallelism of LBM well, which led to high efficiency of GPU on the LBM solver. At the same time, it bronght possibility for large-scale DNS on the desk-top supercomputer. In this DNS work, 8 GPUs were adopted. The number of meshes is 6.7×107, which resulted in a non-dimensional mesh size of Δ+=1.41 for the whole solution domain. It took only 24 hours for the GPU-LBM solver to simulate 3×106 LBM steps. As a result, both the mean velocity and turbulent variables, such as Reynolds stress and velocity fluctuations, agree well with the results of Moser, et al. The capacity and validity of LBM in simulating turbulent flow are verified.
Numerical Research on Flow and Heat Transfer Performance in Rotating Channel With Hemispherical Dimples or Protrusions
ZHANG Da-hai, LI Guo-qiang, XIE Gong-nan, SHI Zhen-chao
2013, 34(9): 965-975. doi: 10.3879/j.issn.1000-0887.2013.09.010
Abstract(1124) PDF(1055)
The convective heat transfer performance of internal cooling passage with hemispherical dimples or protrusions was numerically studied and the influence of Coriolis force on heat transfer characteristics in the channel flow was explored. It is found that: the leading edge of the channel shows weak flow impact with the increase of the rotation number, but there is a big wake and delayed flow reattachment; a smaller vortex and stronger jet exist in the dimple of the trailing edge, which make the heat transfer augmentation up to a maximum of 60%. With the increase of the rotation number, the overall Nusselt number decreases firstly and then increases.
Analysis of Vortex-Induced Vibration Characteristics for a Three Dimensional Flexible Tube
FENG Zhi-peng, ZHANG Yi-xiong, ZANG Feng-gang, YE Xian-hui
2013, 34(9): 976-985. doi: 10.3879/j.issn.1000-0887.2013.09.011
Abstract(1090) PDF(1030)
Numerical simulations of vortex-induced vibration of a three-dimensional flexible tube under uniform turbulent flow were calculated when Reynolds number was 1.35×104. In order to achieve the vortex-induced vibration, the three-dimensional unsteady, viscous, incompressible Navier-Stokes equation and LES turbulence model were solved in the finite volume approach, the tube was discretized according to the finite element theory, and its dynamic equilibrium equations were solved by the Newmark method. The fluid-tube interaction was realized by the diffusion-based smooth dynamic mesh method. For a VIV system, the varying trends of lift coefficient, drag coefficient, displacement, vortex shedding frequency, phase difference angle of the tube were analyzed at different frequency ratios. The nonlinear phenomena of lock-in and phase-switch were captured successfully. Meanwhile, the limit cycle and bifurcation of the lift coefficient and displacement were analyzed with trajectory, phase portrait and Poincaré section mapping. The results reveal that: when the drag coefficient reaches its minimum value, the transverse vibration amplitude reaches its maximum and lock-in begins simultaneously. In the range of lock-in, the vibration amplitude decreases gradually with increase of the frequency ratio. When the lift coefficient reaches its minimum value, the phase difference between the lift coefficient and lateral displacement undergoes a sudden change from an out-of-phase to an in-phase mode. There is no bifurcation of the lift coefficient and lateral displacement occurring to the three dimensional flexible tube under uniform turbulent flow.
Constraint Equation Method for Analysis of Removing Temporary Supports From LargeSpan Steel Roof
GUO Xiao-nong, QIU Li-qiu, LUO Yong-feng, YE Zhi-wu, LUO Li-sheng
2013, 34(9): 986-994. doi: 10.3879/j.issn.1000-0887.2013.09.012
Abstract(1255) PDF(923)
Four calculation methods for numerical simulation analysis of removing temporary supports from large-span steel roof were introduced——support displacement method, equivalent rod bottom-end displacement method, jack element method and jack-gap element method. Then a new method, constraint equation method, was proposed. All the methods mentioned above were used separately to analyze the process of removing temporary supports from a three-point-support beam which was fixed at both ends. The comparisons of results obtained by these methods indicate that the proposed constraint equation method is rational and effective for accurate simulation analysis of removing temporary supports to steel structural roof.
Parameter-Adjusting Method of Constructing Birkhoffian Functions
SONG Duan, LIU Chang, GUO Yong-xin
2013, 34(9): 995-1002. doi: 10.3879/j.issn.1000-0887.2013.09.013
Abstract(1197) PDF(953)
The parameter-adjusting method to construct dynamical functions of Birkhoff's equations is put forward based on realizing the completeness of Birkhoff’s equations, which are under-determinate, by means of Cauchy-Kovalevski integrability theorem for partial differential equations. The two kinds of parameters in the compensatory equation were capable of adjusting to get different sets of Birkhoffian functions. The existing methods, such as Hojman’s method using 2n-first integrals for dynamical systems with symmetry, were compared with the parameter-adjusting method. Finally, The compensatory equation for the Birkhoff's equations can be simplified by means of some limitations on the two kinds of parameters, where the relation between the Birkhoffian functions and parameters become more evident.