Table of Content

18 November 2007, Volume 28 Issue 11

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Articles

Numerical simulation of flow in Hartmann resonance tube and flow in ultrasonic gas atomizer

LI Bo;HU Guo-hui;ZHOU Zhe-wei

2007, 28(11):  1415-1426 .  doi:10.1007/s10483-007-1101-6

Abstract ( 1109 )   PDF (530KB) ( 403 )  

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The gas flow in the Hartmann resonance tube is numerically investigated by the finite volume method based on the Roe solver. The oscillation of the flow is studied with the presence of a needle actuator set along the nozzle axis. Numerical results agree well with the theoretical and experimental results available. Numerical results indicate that the resonance mode of the resonance tube will switch by means of removing or adding the actuator. The gas flow in the ultrasonic gas atomization (USGA) nozzle is also studied by the same numerical methods. Oscillation caused by the Hartmann resonance tube structure, coupled with a secondary resonator, in the USGA nozzle is investigated. Effects of the variation of parameters on the oscillation are studied. The mechanism of the transition of subsonic flow to supersonic flow in the USGA nozzle is also discussed based on numerical results.

Law of nonlinear flow in saturated clays and radial consolidation

DENG Ying-er;XIE He-ping;HUANG Run-qiu;LIU Ci-qun

2007, 28(11):  1427-1436 .  doi:10.1007/s10483-007-1102-7

Abstract ( 1604 )   PDF (167KB) ( 472 )  

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It was derived that micro-scale amount level of average pore radius of clay changed from 0.01 to 0.1 micron by an equivalent concept of flow in porous media. There is good agreement between the derived results and test ones. Results of experiments show that flow in micro-scale pore of saturated clays follows law of nonlinear flow. Theoretical analyses demonstrate that an interaction of solid-liquid interfaces varies inversely with
permeability or porous radius. The interaction is an important reason why nonlinear flow in saturated clays occurs. An exact mathematical model was presented for nonlinear flow in micro-scale pore of saturated clays. Dimension and physical meanings of parameters of it are definite. A new law of nonlinear flow in saturated clays was established. It can describe characteristics of flow curve of the whole process of the nonlinear flow from low hydraulic gradient to high one. Darcy law is a special case of the new law. A mathematical model was presented for consolidation of nonlinear flow in radius direction in saturated clays with constant rate based on the new law of nonlinear flow. Equations of average mass conservation and moving boundary, and formula of excess pore pressure distribution and average degree of consolidation for nonlinear flow in saturated clay were
derived by using an idea of viscous boundary layer, a method of steady state in stead of transient state and a method of integral of an equation. Laws of excess pore pressure distribution and changes of average degree of consolidation with time were obtained. Results show that velocity of moving boundary decreases because of the nonlinear flow in saturated clay. The results can provide geology engineering and geotechnical engineering
of saturated clay with new scientific bases. Calculations of average degree of consolidation of the Darcy flow are a special case of that of the nonlinear flow.

Blow-up of solution for a generalized Boussinesq equation

WANG Yan-ping;GUO Bo-ling

2007, 28(11):  1437-1443 .  doi:10.1007/s10483-007-1103-y

Abstract ( 1518 )   PDF (368KB) ( 356 )  

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This paper studies the initial boundary value problem for a generalized Boussinesq equation and proves the existence and uniqueness of the local generalized solution of the problem by using the Galerkin method. Moreover, it gives the sufficient conditions of blow-up of the solution in finite time by using the concavity method.

Nanoparticle coagulation in a planar jet via moment method

YU Ming-zhou;LIN Jian-zhong;CHEN Li-hua

2007, 28(11):  1445-1453 .  doi:10.1007/s10483-007-1104-8

Abstract ( 1266 )   PDF (122KB) ( 483 )  

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Large eddy simulations of nanoparticle coagulation in an incompressible planar jet were performed. The particle is described using a moment method to approximate the particle general dynamics equations. The time-averaged results based on 3000 time steps for every case were obtained to explore the influence of the Schmidt number and the Damkohler number on the nanoparticle dynamics. The results show that the changes of Schmidt number have the influence on the number concentration of nanoparticles only when the particle diameter is less than 1 nm for the fixed gas parameters. The number concentration of particles for small particles decreases more rapidly along the flow direction, and the nanoparticles with larger Schmidt number have a narrower distribution along the transverse direction. The smaller nanoparticles coagulate and disperse easily, grow rapidly hence show a stronger polydispersity. The smaller coagulation time scale can enhance the particle collision and coagulation. Frequented collision and coagulation bring a great increase in particle size. The larger the Damkohler number is, the higher the particle polydispersity is.

Travelling wave solutions for a second order wave equation of KdV type

LONG Yao;LI Ji-bin;RUI Wei-guo;HE Bin

2007, 28(11):  1455-1465 .  doi:10.1007/s10483-007-1105-y

Abstract ( 1278 )   PDF (234KB) ( 315 )  

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MHD flow and heat transfer from continuous surface in uniform free stream of non-Newtonian fluid

Bikash Sahoo;H. G. Sharma

2007, 28(11):  1467-1477 .  doi:10.1007/s10483-007-1106-z

Abstract ( 1509 )   PDF (169KB) ( 504 )  

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Nonlinear analysis of a structure loaded by a stochastic excitation

GAO Shi-qiao;JIN Lei;M. Kasperski;LIU Hai-peng;LI Ming-hui

2007, 28(11):  1479-1485 .  doi:10.1007/s10483-007-1107-y

Abstract ( 1193 )   PDF (152KB) ( 360 )  

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For a non-linear system excited by a stochastic load which is expressed as a time series, a recursive method based on the Z-transform is presented. To identify the obtained response time series, a discrete wavelet transform (DWT) technique is proposed.

Structural first failure times under non-Gaussian stochastic behavior

HE Jun

2007, 28(11):  1487-1494 .  doi:10.1007/s10483-007-1108-9

Abstract ( 1347 )   PDF (210KB) ( 376 )  

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An analytical moment-based method for calculating structural first failure times under non-Gaussian stochastic behavior is proposed. In the method, a power series that constants can be obtained from response moments (skewness, kurtosis, etc.) is used firstly to map a non-Gaussian structural response into a standard Gaussian process, then mean up-crossing rates, mean clump size and the initial passage probability of a critical
barrier level by the original structural response are estimated, and finally, the formula for calculating first failure times is established on the assumption that corrected up-crossing rates are independent. An analysis of a nonlinear single-degree-of-freedom dynamical
system excited by a Gaussian model of load not only demonstrates the usage of the proposed method but also shows the accuracy and efficiency of the proposed method by comparisons between the present method and other methods such as Monte Carlo simulation and the traditional Gaussian model.

Some new conditions for generalized H-matrices

ZHU Li;LIU Jian-zhou

2007, 28(11):  1495-1501 .  doi:10.1007/s10483-007-1109-y

Abstract ( 1125 )   PDF (156KB) ( 535 )  

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By using a continuous transition method of a matrix and the estimate for spectral radius of a sub-matrix etc., decision methods for a generalized H-matrix under positive definite matrix conditions are researched. Some new sufficient conditions for generalized H-matrices are obtained. When a block matrix degenerates a point matrix, these conditions namely become sufficient conditions of H-matrix.

Schauder estimates for parabolic equation of bi-harmonic type

YAO Feng-ping;ZHOU Shu-lin

2007, 28(11):  1503-1516 .  doi:10.1007/s10483-007-1110-z

Abstract ( 1332 )   PDF (171KB) ( 458 )  

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Global Schauder estimates for the initial-value parabolic problem of the bi-harmonic type are proved, and the existence and uniqueness of the solutions in the suitable space are obtained. Similarly to the second-order case, first a formal expression of solutions by the Fourier transform is obtained, and then the regularity, uniqueness and existence of solutions using the potential theory and approximation argument are got. out approach is simple and straightforward.

Bifurcations of double homoclinic flip orbits with resonant eigenvalues

ZHANG Tian-si;ZHU De-ming

2007, 28(11):  1517-1526 .  doi:10.1007/s10483-007-1111-y

Abstract ( 1224 )   PDF (264KB) ( 475 )  

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Concerns double homoclinic loops with orbit flips and two resonant eigenvalues in a four-dimensional system. We use the solution of a normal form system to construct a singular map in some neighborhood of the equilibrium, and the solution of a linear variational system to construct a regular map in some neighborhood of the double homoclinic loops, then compose them to get the important Poincare map. A simple calculation gives explicitly an expression of the associated successor function. By a delicate analysis of the bifurcation equation, we obtain the condition that the original double homoclinic loops are kept, and prove the existence and the existence regions of the large 1-homoclinic orbit bifurcation surface, 2-fold large 1-periodic orbit bifurcation surface, large 2-homoclinic orbit bifurcation surface and their approximate expressions. We also locate the large periodic orbits and large homoclinic orbits and their number.

Random attractors for asymptotically upper semicompact multivalue random semiflows

LI Ting

2007, 28(11):  1527-1534 .  doi:10.1007/s10483-007-1112-z

Abstract ( 1208 )   PDF (338KB) ( 369 )  

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Instantaneous spectrum estimation of earthquake ground motions based on unscented Kalman filter method

LI Ying-min;DONG Yin-feng;LAI Ming

2007, 28(11):  1535-1543 .  doi:10.1007/s10483-007-1113-5

Abstract ( 1107 )   PDF (227KB) ( 461 )  

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Lagrange-Maxwell equation and magnetic saturation parametric resonance of generator set

YANG Zhi-an;LI Wen-lan;QIU Jia-jun;XI Xiao-yan

2007, 28(11):  1545-1553 .  doi:10.1007/s10483-007-1114-y

Abstract ( 1268 )   PDF (193KB) ( 607 )  

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Lagrange-Maxwell's equation is extended firstly. With the theory of electromechanical analytical dynamics, the magnetic complement energy in air gap of generator is acquired. The torsional vibration differential equations with periodic coefficients of rotor shafting of generator which is in the state of magnetic saturation are established. It is shown that the= magnetic saturation may cause double frequency electromagnetic moment. By means of the averaging method, the first approximate solution and corresponding solution of the primary parametric resonance is obtained. The characteristics and laws of the primary parametric resonance excited by the electromagnetism are analyzed and some of new phenomena are revealed.