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2013年 第34卷 第3期    刊出日期：2013-03-03

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Attractive fixed-point solution study of shell model for homogeneous isotropic turbulence

郭昊 李超 屈秋林 刘沛清

2013, 34(3):  259-268.  doi:10.1007/s10483-013-1668-x

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The attractive fixed-point solution of a nonlinear cascade model is studied for the homogeneous isotropic turbulence containing a parameter C, introduced by Desnyansky and Novikov. With a traditional constant positive external force added on the first shell equation, it can be found that the attractive fixed-point solution of the model depends on both the parameter C and the external force. Thus, an explicit force is introduced to remove the effects of the external force on the attractive fixed-point solution. Furthermore, two groups of attractive fixed-point solutions are derived theoretically
and studied numerically. One of the groups has the same scaling behavior of the velocity in the whole inertial range and agrees well with those observed by Bell and Nelkin for the nonnegative parameters. The other is found to have different scaling behaviors of the velocity at the odd and even number shells for the negative parameters. This special characteristic may be used to study the anomalous scaling behavior of the turbulence.

论文

Nonlinear vibration of embedded single-walled carbon nanotube with geometrical imperfection under harmonic load based on nonlocal Timoshenko beam theory

王博 邓子辰 张凯

2013, 34(3):  269-280.  doi:10.1007/s10483-013-1669-8

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Based on the nonlocal continuum theory, the nonlinear vibration of an embedded single-walled carbon nanotube (SWCNT) subjected to a harmonic load is investigated. In the present study, the SWCNT is assumed to be a curved beam, which is unlike previous similar work. Firstly, the governing equations of motion are derived by the Hamilton principle, meanwhile, the Galerkin approach is carried out to convert the nonlinear integral-differential equation into a second-order nonlinear ordinary differential equation. Then, the precise integration method based on the local linearzation is appropriately designed for solving the above dynamic equations. Besides, the numerical example is presented, the effects of the nonlocal parameters, the elastic medium constants, the waviness ratios, and the material lengths on the dynamic response are analyzed. The results show that the above mentioned effects have influences on the dynamic behavior of the SWCNT.

Experimental study of wind loads on cylindrical reticulated shells

黄鹏 周晅毅 顾明

2013, 34(3):  281-296.  doi:10.1007/s10483-013-1670-6

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The cylindrical reticulated shell structures without side walls, which are normally arranged in pairs, are usually used as dry-coal sheds in a thermal power plant. The wind loads of these shells do not exist in standards or codes. Therefore, this study investigates the mean and fluctuating wind loads on a cylindrical reticulated shell with a rise-to-span ratio of 0.39 through a series of wind tunnel tests. The characteristics of
the wind pressures on the upper and lower surfaces and the net pressures are presented. The results show that the wind direction and another shell structure significantly affect the wind loads on the principal shell. The most unfavorable wind direction is around 30^?, whereas the effects of the wind field and the height of the coal stack are small. The surfaces of the shells are divided into nine blocks, and the block mean and fluctuating
(rms) pressure coefficients suitable for engineering applications are given as references for wind load codes.

Thickness-averaged model for numerical simulation of electroosmotic flow in three-dimensional microfluidic chips

陈波 陈瀚 吴健康

2013, 34(3):  297-308.  doi:10.1007/s10483-013-1671-8

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The microfluidic system is a multi-physics interaction field that has attracted great attention. The electric double layers and electroosmosis are important flow-electricity interaction phenomena. This paper presents a thickness-averaged model to solve three-dimensional complex electroosmotic flows in a wide-shallow microchannel/chamber combined (MCC) chip based on the Navier-Stokes equations for the flow
field and the Poisson equation to the electric field. Behaviors of the electroosmotic flow, the electric field, and the pressure are analyzed. The quantitative effects of the wall charge density (or the zeta potential) and the applied electric field on the electroosmotic flow rate are investigated. The two-dimensional thickness-averaged flow model greatly simplifies the three-dimensional computation of the complex electroosmotic flows, and
correctly reflects the electrookinetic effects of the wall charge on the flow. The numerical results indicate that the electroosmotic flow rate of the thickness-averaged model agrees well with that of the three-dimensional slip-boundary flow model. The flow streamlines and pressure distribution of these two models are in qualitative agreement.

Linear stability of triple-diffusive convection in micropolar ferromagnetic fluid saturating porous medium

S. CHAND

2013, 34(3):  309-326.  doi:10.1007/s10483-013-1672-9

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The triple-diffusive convection in a micropolar ferromagnetic fluid layer heated and soluted from below is considered in the presence of a transverse uniform magnetic field. An exact solution is obtained for a flat fluid layer contained between two free boundaries. A linear stability analysis and a normal mode analysis method are carried out to study the onset convection. For stationary convection, various parameters such as the medium permeability, the solute gradients, the non-buoyancy magnetization, and the micropolar parameters (i.e., the coupling parameter, the spin diffusion parameter, and the micropolar heat conduction parameter) are analyzed. The critical magnetic thermal Rayleigh number for the onset of instability is determined numerically for a sufficiently large value of the buoyancy magnetization parameter M1. The principle of exchange of stabilities is found to be true for the micropolar fluid heated from below in the absence of the micropolar viscous effect, the microinertia, and the solute gradients. The
micropolar viscous effect, the microinertia, and the solute gradient introduce oscillatory modes, which are non-existent in their absence. Sufficient conditions for the non-existence of overstability are also obtained.

Numerical simulation of avascular tumor growth based on p27 gene regulation

周瑜 陈佳婉 戴晓宁 蔡彦 姚伟 许世雄 龙泉

2013, 34(3):  327-338.  doi:10.1007/s10483-013-1673-6

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A multi-scale continuous-discrete model based on the effects of the p27 gene control is built to simulate the avascular tumor growth. At the tissue level, the continuous Eulerian model is adopted to determine the distribution of the concentration of oxygen, the extracellular matrix (ECM), and the matrix-degradative enzyme (MDE). At the cellular level, the discrete Lagrangien model is adopted to determine the movement, the proliferation, and the death of single tumor cells (TCs). At the genetic level, whether a cell is committed to mitosis is determined by solving a set of equations modeling the effects of the p27 gene control. The avascular morphological evolution of the solid tumor growth is simulated, including the radius of the solid tumor, the number of the TCs, the oxygen distribution over time, and the inhibiting effect of the up-regulating p27 gene expression.

Mixed convection heat transfer in horizontal channel filled with nanofluids

樊涛 徐航 I. POP

2013, 34(3):  339-350.  doi:10.1007/s10483-013-1674-9

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The laminar fully developed nanofluid flow and heat transfer in a horizonal channel are investigated. Highly accurate solutions for the temperature and nanoparticle concentration distributions are obtained. The effects of the Brownian motion parameter Nb, the thermophoresis parameter Nt, and the Lewis number Le on the temperature and nanoparticle concentration distributions are discussed. The current analysis shows that the nanoparticles can improve the heat transfer characteristics significantly for this flow problem.

Predicting air pressure in drainage stack of high-rise building

E. S. W. WONG 李应林 朱祚金

2013, 34(3):  351-362.  doi:10.1007/s10483-013-1675-7

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It is necessary to understand the features of air pressure in a drainage stack of a high-rise building for properly designing and operating a drainage system. This paper presents a mathematical model for predicting the stack performance. A step function is used to describe the effect of the air entrainment caused by the water discharged from branch pipes. An additional source term is introduced to reflect the gas-liquid interphase
interaction (GLII) and stack base effect. The drainage stack is divided into upper and base parts. The air pressure in the upper part is predicted by a total variation diminishing (TVD) scheme, while in the base part, it is predicted by a characteristic line method (CLM). The predicted results are compared with the data measured in a real-scale highrise test building. It is found that the additional source term in the present model is
effective. It intensively influences the air pressure distribution in the stack. The air pressure is also sensitive to the velocity-adjusting parameter (VAP), the branch pipe air entrainment, and the conditions on the stack bottom.

Modeling of anisotropic polydispersed composites by progressive micromechanical approach

A. MOHYEDDIN A. FEREIDOON

2013, 34(3):  363-370.  doi:10.1007/s10483-013-1676-6

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A progressive micromechanical method is presented in order to predict the elastic constants of polydispersed composites including multi-directional or randomly oriented reinforcement particles. Heterogeneities of various types are introduced into the matrices in a gradual manner. At each step, the Mori-Tanaka method is used to obtain the stiffness tensor of the intermediate medium used as a matrix of the following step. The proposed method is capable of introducing any kind of heterogeneities based on their dimensions, orientations, mechanical properties, and volume fractions to the matrix. Furthermore, suitable probability density functions can be defined for physical and structural parameters of the composite, including the level of the filler-matrix interfacial bonding, the aspect ratio, and the orientation of reinforcement particles. The efficiency of the iterative approach and the convergence of the solution are studied by computing the stiffness tensors of unidirectional and bidirectional particulate composites. The results of the present study are also compared with the literature data for a randomly oriented particulate composite.

H¹ space-time discontinuous finite element method for convection-diffusion equations

何斯日古楞 李宏 刘洋

2013, 34(3):  371-384.  doi:10.1007/s10483-013-1677-x

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An H¹ space-time discontinuous Galerkin (STDG) scheme for convectiondiffusion equations in one spatial dimension is constructed and analyzed. This method is formulated by combining the H¹   Galerkin method and the space-time discontinuous finite element method that is discontinuous in time and continuous in space. The existence and the uniqueness of the approximate solution are proved. The convergence of the scheme is analyzed by using the techniques in the finite difference and finite element methods. An optimal a-priori error estimate in the L∞(H¹  ) norm is derived. The numerical experiments are presented to verify the theoretical results.

Global attractor of 2D autonomous g-Navier-Stokes equations

姜金平 王小霞

2013, 34(3):  385-394.  doi:10.1007/s10483-013-1678-7

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In this paper, the existence of global attractors for the 2D autonomous g-Navier-Stokes equations on multi-connected bounded domains is investigated under the general assumptions of boundaries. The estimation of the Hausdorff dimensions for global attractors is given.