EI、Scopus 收录

2009 Vol. 41, No. 3

Display Method:
Perturbation analysis of liquid flows in micro-channels driven by high pressures
Jian Li, Jinbai Zhang, Chun-Hian Lee
An asymptotic expansion of compressible N-S equations werededuced via parametric expansion, and liquid flow characteristics under highdriven pressures in long micro-channels with arbitrary cross sections wereanalyzed by solving the zeroth order equations. The contributions due tocross section, length of the wall-slip, and other related factors were takeninto account by solving the Green's function over the cross section. A setof zeroth order solutions for circular cylinders of constant cross sectionwere presented, and the influences of the compressibility and viscosity ofthe liquids, and the slip length on the flow characteristics inmicro-channels under high pressure were studies.
2009, 41(3): 289-299. doi: 10.6052/0459-1879-2009-3-2008-276
A numerical study on resistance characteristics of flow around two cylinders
Xiangjun Liu, Jian Zhang, Chao Lin
Lattice Boltzmann models (LBM) is a recently developedmethod in computational fluid dynamics, and it is particularly suitable forflow modeling in complex boundary area. In this paper, the resistancecharacteristics of gas flow around two cylinders are numerically studiedusing LBM. The drag force and drag coefficient of each cylinder are studiedby varying the cylinder distance, Reynold number, and the attack angle.Three typical scenarios are studies: The first scenario is to calculate10 typical cases with the cylinder distance varying from 1.2d to 3.0d wherethe Reynolds number is fixed to be 20. The calculated results show that thesmallest stress acting on the downstream cylinder exists when the cylinderdistance is between 1.2d and 1.4d. Furthermore, the minimum total drag forceacting on the two cylinders occurs when cylinder distance is 1.6d. We alsofound that the downstream cylinder has no impact on resistance coefficientof upstream cylinder when the cylinder distance is greater than 2d. Thesecond scenario is to study the effects of Reynolds number on the resistancecharacteristics of the two cylinders by fixing the cylinder distance as1.2d. Results show that the weakest stress on the secondary cylinder intandem arrangement exists at a point where the Reynolds number is between 30and 40. The results in the third scenarioshow that the attack angle has great effect on the resistance coefficient ofeach cylinder. These reasonable results can server as the scientificfoundation for further research and implementation of flow overmulti-cylinders under low Reynold numbers.
2009, 41(3): 300-306. doi: 10.6052/0459-1879-2009-3-2007-494
Hydrodynamic stability of a liquid wavy film with interfacial shear
Xuemin Ye, Chunxi Li, Songlin Wang
The hydrodynamic stability of a liquid wavy film isimportant to guarantee its function for efficient heat and mass transfer.However, the stability has been affected by various factors. Under a gasflow at the gas-liquid interface, the stability is obviously influenced bythe interfacial shear at the boundary condition. The evolution equation ofthe surface waves under shear effect is derived with the integral approachbased on the boundary layer theory, and the effect of interfacial shear onthe stability under different conditions is illustrated with the presentmodel. The theoertical results show that film flow tends to be unstableunder the cocurrent shear, and the effect of countercurrent shear plays apositive role under lower Re and a negative role under higher Re. Thecritical wave number and critical wave velocity increase under the cocurrentshear and decrease under countercurrent shear. Therefore, the effect ofinterfacial shear on critical wave velocity is clearly different underdifferent Reynolds number.
2009, 41(3): 307-312. doi: 10.6052/0459-1879-2009-3-2007-594
A model for the flow of emulsion in porous media with micro-heterogeneities
Xiaobo Li, Yuewu Liu, Hongzhi Sheng, Ruyong Feng
The flow of crude oil-water emulsion in porous media iscommon phenomena in the process of alkali-surfactant-polymer (ASP) floodingand thermal oil recovery. Microscopic structural characteristics of porousmedia show crucial effects on the flow of emulsion. Existing theoreticalmodels on the flow of emulsion in porous media are deterministic approachesto describe macroscopic volume-averaged performance of porous media withmicroscopic structures. There are inherent deviations between deterministicdescriptions and experimental results when smaller-scale heterogeneities cannot be omitted with the comparison of the size of porous media. In thispaper, a stochastic method on the flow of emulsion in porous media isdeveloped based on continuous time random walk (CTRW) formalism. Theprobability distribution functions of transition time and displacement ofdispersed-phase droplets give description of microscopic heterogeneities ofporous media. The results show that present model can effectively describethe scale-dependent long-tailed phenomena of experimental results and beused as general filtration model.
2009, 41(3): 313-317. doi: 10.6052/0459-1879-2009-3-2008-027
A 3D modeling of water-sediment two-phase movement in flat-bed channel bends
Cheng Liu, Yongming Shen
Sediment flow and transport in natural rivers are ofconsiderable interest in the field of river engineering. Generally, thereare many channel bends in natural rivers. The flow characteristics andsediment movement are much more complex in channel bends than in straightchannels. In order to study the development of water-sediment movement inchannel bend, a three-dimensional k-ε-kp solid-liquidtwo-phase two-fluid turbulence (STTT) model in curvilinear coordinatesis solved numerically with a finite-volume method on an adaptive grid.The k-ε-kp STTT model wasintroduced by Zhou and it consists of a Boussinesq expression with scalarviscosity coefficients to model STTT Reynolds stresses and particleturbulence flux. The water flow in an S-shaped flume was first used toverify liquid-phase model and the velocities of water flow were wellreproduced by the model. The secondary flow has different magnitude alongthe S-shaped flume. Then the model was used to calculate the movements ofwater and sediment in a 120°channel bend. From both experimental dataand numerical results, it was shown that the sediment shares the samestreamlines of water in the straight zone and deviates from the streamlinesof water at the channel bend. The deviation increases with the increase ofsediment particle diameters. The numerical results of solid-liquid two-phaseflow in an S-shaped flume have shown that the longitudinal velocities ofsolid-phase are bigger than those of liquid-phase near walls and smallerthan those of liquid-phase in other zones, while the transverse velocitiesof solid-phase are smaller than those of liquid-phase, and the verticalvelocities are almost equal to fall velocities of sediments in straightsections and change much in the bends under the action of helical flows. Inaddition, the concentration of sediment is bigger in the bottom than that inthe surface and also bigger in the inner bank of the S-shaped flume thanthat in the outer bank.
2009, 41(3): 318-328. doi: 10.6052/0459-1879-2009-3-2007-595
Experimental investigation of Bénard-Marangoni convection of two-layer fluid
Lujun Li, Li Duan, Liang Hu, Qi Kang
In this paper, the Bénard-Marangoni convection in the two-layerfluid is investigated experimentally with particle image velocimetry (PIV).Different convection patterns near the critical point are observed.Meanwhile, the transitions from critical convection to supercriticalconvection are studied when the temperature difference $\Delta T$ is rampedslowly. The experimental results indicate that the interface tension playsan important role for the convective patterns near critical point and thetransition of the convection patterns of two-layer fluid.
2009, 41(3): 329-336. doi: 10.6052/0459-1879-2009-3-2008-037
Numerical study on hemodynamic in an S-type arterial end-to-side anastomosis with taylor patch
Wentao Feng, Wentao Jiang, Yubo Fan, Xiaoyan Deng, Jinchuan LiJ, unkai Chen
In order to clarify the influence of Taylor patch onthe flow field in a new (S-type) arterial end-to-side anastomosis, anumerical investigation was carried out in terms of the flow patterns, wallshear stresses, and wall shear stresses gradients. The numerical resultsshowed that the Taylor patch had an great effect on the flow field at thedistal anastomosis. At the distal anastomosis, more smooth distributions offlow patterns were obtained, and the second flow and the wall shear stressgradients decreased almost 34.48% and 52.22%, respectively, to improvethe haemodynamics, while at the artery bottom the wall shear stress wasreduced about 30.33% to promote atherosclerosis. Therefore, it can not beconcluded that the Taylor patch has superior treatment in S-type bypassgraft by only considering haemodynamic factors. Moreover, a lot of animaland clinical experiments are needed to be carried out with numerical study.
2009, 41(3): 337-341. doi: 10.6052/0459-1879-2009-3-2008-105
Influence of water molecule diffusion resistance force on electro-actuating characteristics of ionic polymer-metal
Yaqi Gong, Jianping Fan, Cheng Wang
Based on the mechanism of Tadokoro model, the dynamicelectro-mechanical response of Ionic polymer-metal composite (IPMC) has beensimulated using finite element method. Generally, the water moleculediffusion force is neglected in the most of the former numerical simulationworks. In the present paper, the influence of water diffusion resistanceforce in the process of the movement of sodium ion has been emphaticallyexplored and compared, by introducing two different governing equations:with and without consideration of water diffusion resistance force. Thewater diffusion resistance force is described as a non-linear term and thecorresponding governing equation is solved by iteration. The numericalresults show that the water diffusion force has no obvious effect on thedisplacement, but significant effect on the sodium ion concentration,effective moisture distribution and internal balance force. In addition, theeffect exhibits the area selection, especially at the region close to theanode and cathode. The predicting accuracy will be improved by involvingthis nonlinear component within the governing equation.
2009, 41(3): 342-349. doi: 10.6052/0459-1879-2009-3-2008-051
An explicit method for numerical simulation of wave motion---1-D wave motion
Zhenpeng Liao, Heng Liu, Zhinan Xie
A new explicit method for numerical simulation of wave motion in time domainis first presented and illustrated by constructing the recursion formulas atnodal points of an irregular grid for 1-D wave equation in this paper. Todemonstrate the possibility to develop stable and high-order formulas withthe method, accuracy and stability of the numerical simulation are firstdiscussed in detail for the 1-D scalar wave equation in a uniform grid, andan approach is then proposed to construct the stable formulas with 2M-orderaccuracy both in time and space. A theoretical case is illustrated byconstructing the formulas of second order (M=1) and fourth order (M=2). Theresults with the proposed method are validated by a series of numericaltests.
2009, 41(3): 350-360. doi: 10.6052/0459-1879-2009-3-2007-635
Instability and breakup of stretching metallic jets
Yina Shi, Chengsen Qin
Based on the Hamilton principle, a coupled motion equationof stretching metallic shaped-charge jet is presented to study the effectsof yield strength, shear, strain rate, viscosity, surface tension force andvelocity gradient on the jet instability, and the results arequantitatively discussed. The value range ofnon-dimensional \lambda _m \dot {\varepsilon }_0 was obtained toillustrate the product of the wavelength in unstablest solution and initialstrain rate. Furthermore, the criterion and approximate theoretical formulaof jet breakup time are presented. The theoretical results were in fairlygood agreement with the jet experimental data and those from the methoddeveloped by Chou and Carleone.
2009, 41(3): 361-370. doi: 10.6052/0459-1879-2009-3-2007-435
A fractal study on meso structures and size effect of metallic foams
Qijian He, Hongwei Song, Chengguang Huang
Meso structure of metallic foam, such as morphologies ofcells, cell walls and pores, is very important to its mechanical properties.Unlike honeycombs and some other cellular solids which have sequential andperiodical cell structures, metallic foams are inherently disordered in thecell level: non-equally sized and various shaped cells, non-equallydimensioned and curvy cell walls, random pores and cracks. It is impracticalto extract a representative cell and build ordered models, and thesimplified homogenous models can not reveal the importance of cellstructures to the global mechanical properties. A common parameter inanalytical models is relative density, which is a macroscopic value thatcannot reveal the meso structure of metallic foam. In this paper, a fractalapproach is introduced to bridge the morphological parameters of cellstructures and the mechanical properties of metallic foams. Cell morphologyof Al foams is proved to be a fractal geometry of self-similar in a certainscale, using the slit island method proposed by Mandelbrot. A series of Alfoams with different relative densities and meso structures were examined bythe box-counting dimension method, the information dimension method and theslit island method. It is found that the fractal dimension is in directproportion to the ratio of characteristic wall thickness to mean celldiameter. By mapping the cell morphology to the generalized Sierpinskicarpet, the mechanical properties of Al foams are expressed as the functionof fractal dimension. In addition, the fractal model is combined with thesize effect model proposed by Onck et al, and the revised size effect modelfor metallic foams incorporates stochastic characteristic of mesostructures. The results show that the fractal-based model can not onlyreveal the variation of yield strength with specimen size, but also bridgethe meso structures and mechanical properties of Al foams directly.
2009, 41(3): 370-375. doi: 10.6052/0459-1879-2009-3-2008-034
A noval stress integration algorithm in inverse analysis method of sheet metal stamping
Bingtao Tang, Deming Sun, Zhaoqing Wang, Zhen Zhao
An improved inverse analysis method is proposed for sheetmetal stamping based on the final workpiece in Euler coordinate system. Theprinciple of the virtual work is firstly adopted to obtain the equivalentequations. The constitutive equation in the present method is based on flowtheory of plasticity to consider the loading history, while deformationtheory of plasticity in the classical inverse analysis method. The plasticmultiplier \Delta \lambda is directly obtained with the concept ofthe equivalent stress in order to avoid numerous iterations inNewton-Raphson scheme \Delta \lambda. The numerical resultsobtained from the classical and improved inverse analysis methods arecompared with those from the incremental forward finite element solverLS-DYNA. It shows that the proposed constitutive equation is effective andreliable with the comparisons of blank configurations, Forming LimitedDiagram (FLD), the effective strain distribution and computationalefficiency.
2009, 41(3): 376-382. doi: 10.6052/0459-1879-2009-3-2007-645
The regression prediction model for the strength of cylinder shell against pulse loading based on support vector machine
Minghui He, Jiacheng Mao, Ruyu Fan, Ping Zhang
Based on experimental data of structural response ofsmall samples, support vector machine (SVM) regression method is employed tosimulate the nonlinear functional relationship among the peak value ofdynamic strain in the cylinder shell, its size and external pulse loading.Meanwhile, an improved simplex-simulated annealing hybrid algorithm isdeveloped to accomplish the optimization of SVM parameters. In addition, thecomparative analysis of forecasting capacity between SVM and backpropagation artificial neural network method is conducted. The theoreticalresults verify that SVM with optimal performance parameters has a betterforecasting capacity under the small sampling condition. Finally, themulti-variable functional relationship between the ultimate strength of thelarge-sized cylinder shell and its size against pulse loading is inferredfrom the SVM regression model. This functional relationship can be served asa referable predication model for the strength analysis of this kind ofcylinder shell devices. Theorefore, the above research shows that SVM willhave wide applications in the mechanical structure analysis, such asstrength predication and reliability analysis.
2009, 41(3): 383-388. doi: 10.6052/0459-1879-2009-3-2007-386
The Study of Possible Mechanism of Myosin II inhibited Cytokinesis of Mammalian Cells
Xiaona Li, Meiwen An, Li Wang, Wenzhou Wu, Weiyi Chen
Adherent mammalian cells experience a series of elaborate,but simple morphological changes during cell division. This complex processwas mediated by mechanics and biological molecules. As a kind of motorproteins, myosin II plays an important role in cell division. Recentinvestigations showed that cells on substrates in the absence of myosin IIalso could finish cytokinesis. However, its mechanism is still unclear.In this study, morphology of NRK cells treated with 0.3%DMSO and 30$\mu$mol blebbistatin (myosin II inhibitor) were investigated quantitatively byusing micro-image collecting and analysis system. Intercellular bridgedynamics was simulated using mechanical model of intercellular bridgethinning coupled with mechanical parameters of NRK cells. The distributionof actin in early cytokinesis was examined using immunofluorescence method.Our results showed that intercellular bridge thinning trajectory andmorphology of cells treated with 30 mol blebbistatin were fundamentallydifferent from cells treated with 0.3%DMSO. The surface tensioncontributed greatly to the trajectory of 30 mol blebbistatin group fromfluid mechanical considerations and the measured mechanical parameters.Immunofluorescence results indicated that a mass of actin was recruited tothe fan-shaped leading lamellipodia of daughter cells from the cytoplasm incells treated with 30 mol blebbistatin.Our study indicated that Laplace pressure determined by mechanicalproperties and the motility of cell orchestrated to dictate awell-controlled cytokinesis of cells in the absence of myosin II.
2009, 41(3): 389-398. doi: 10.6052/0459-1879-2009-3-2008-656
Solution of generalized density evolution equation via a family of δsequences
Wenliang Fan, Jie Li
In the stochastic dynamics, it is one of the mostimportant purposes to acquire the probability density function and itsevolution process of the stochastic responses. The probability densityfunction of the responses or state vector of a stochastic dynamical systemis usually governed by some type of probability density evolution equationssuch as the Liouville, FPK or the Dostupov-Pugachev equation. However, theseequations in high dimension are too hard to obtain the solutions. Thegeneralized density evolution equation (GDEE), of which the dimension isindependent to the original dynamical system, provides a new possibility oftackling nonlinear stochastic systems. In this paper, based on the formalsolution of the GDEE, introducing the asymptotic sequences of the Diracδ function, a new numerical solution for the GDEE δ isproposed, to name as the Solution of GDEE via a family of δSequences. In addition, it is found that the non-parameter densityestimation can be regarded as a specific case of the proposed method. Atlast, the rationality and effectiveness of the proposed method is verifiedby some cases.
2009, 41(3): 398-409. doi: 10.6052/0459-1879-2009-3-2007-657
Experimental study of variable structure control in time-delay for a flexible beam under forced vibration
Longxiang Chen, Guoping Cai
Delayed feedback control is a novel and effectivestrategy in time-delay system. This paper presents an experimental study ofdelayed feedback control with a flexible cantilever beam And develop amultiple time-delays controller. First, the system state equation withmultiple time delays is discretized and transformed into a standard discreteform without explicit time delay by a particular augmenting for statevariables. Second, a time-delay controller is designed using the variablestructure control method. Furthermore, piezoelectric (PZT) patches are usedas actuators and exciter, and foil gauges are used as sensors in theexperiments with single and double time delays. The feasibility andefficiency of delayed feedback control method are verified boththeoretically and experimentally.
2009, 41(3): 410-417. doi: 10.6052/0459-1879-2009-3-2008-459
Optimization design of waverider based on the artificial neural networks
Fengtao Zhang, Kai Cui, Guowei Yang, Yuanyuan Cui
Waveriders are supersonic or hypersonic lifting configurations. They areextensively utilized as the forebody part of hypersonic vehicles. As thecore component to generate the lift and compress the incoming flow, awaverider should be designed for assuring the high performance of a vehicle.Various optimization works had been carried out to improve the aerodynamicperformance. However, most of the optimization procedures are often timeconsuming and unstable when the computational fluid dynamic (CFD) analysisis employed for directly evaluating aerodynamic performance. To aim at thisproblem, an artificial neural networks (ANN) based response surface methodwas proposed. First of all, a number of waverider shapes are chose as thenet-training samples, and the aerodynamic performance of each sample isevaluated by CFD analysis. Next, with respect to the training couple, thecontrol parameters of each waverider and its aerodynamic coefficients areprovided to a pre-constructed ANN. The weight of each connection in the ANNis adjusted until the error between the ANN output and the CFD result areacceptable for every training couple. Finally, the ANN is embedded in theoptimization loop as the response surface of the time consuming CFDprocedure. Two numerical cases in the design point of Mach 6 and Reynoldsnumber 7$\times$10$^6$ are carried out to validate the presented method, asingle-objective optimization for maximize the lift-to-drag ratio ($L/D$), anda multi-objective problem to improve the integrated performance of awaverider with the maximal $L/D$, the maximal cubage, and the minimal wetarea. The numerical results show that the ANN based response surface methodis stable with lower time consuming.
2009, 41(3): 418-424. doi: 10.6052/0459-1879-2009-3-2008-422
Stress analysis of star cracks
Zhu Chen, Guanting Liu, Lu Guan
This paper deals with the elastic problem about starcracks using the technique of conformal mapping with complex variablefunction method. The analytic solutions of the stress intensity factors areobtained for mode I and mode II problems at the crack tip. The present modelcan be used to simulate the well-known Griffith cracks, the three straightcracks with common point and uniform distribution, the cross crack andtheeight symmetry straight cracks.
2009, 41(3): 425-430. doi: 10.6052/0459-1879-2009-3-2007-528
A structural topological optimization method with variable displacement constraint limits
Jianhua Rong, Xiaojuan Xing, Guo Deng
In each sub-loop solving of the ICM (Independent,Continuous and Mapping) method, whether in what quantities do topologydesign variables change, structural displacements etc. characteristicquantities and their derivatives are approximately obtained by using theirvalues at the beginning of the sub-loop iterations. This measurement maylead to large errors of the mentioned quantity estimations. If there is onlya type of constraints (such as displacement constraints) in an optimizationmodel, the errors may be larger. In order to deal with this problem, for thestructural topological optimization problem with the objective functionbeing the structural weight and only displacement constraints, this paperproposes a new structural topological optimization method, being based onthe ideas of the ICM method (Independent, Continuous and Mapping) and theevolutionary structural optimization method. New displacement constraintlimits are formed and introduced to the optimization model at the beginningstep of each sub-loop iterations to control variations of topological designvariables. Moreover, the element deletion and adding criterion and a set ofstructural optimization strategy are given. Some elements with artificialmaterial property are inserted around the cavities and boundaries of thestructure optimized so that the structure optimized is a non singularstructure and the proposed method is of an element restorable function. Anda structural characteristics mapping transformation relation between theeffective structure and the structural maximum design domain is built.Incorporating the dual programming method, a new continuum structuraltopological optimization method is proposed. The several examples show thatthere is not any objective oscillation phenomenon in optimizationiterations, and the proposed method is of validity and effectiveness.
2009, 41(3): 431-439. doi: 10.6052/0459-1879-2009-3-2007-418
Semi-analytical solution of seismic response of serially isolated equipment and supporter
Yongfeng Du, Yanhui Liu, Hui Li
Serially isolated system of electrical equipment andsupporter is presented by in-parallel laminated rubber support and themechanical model of this system is developed. Based on the vibration theoryof beam with distributed parameters and the boundary conditions ofconcentrated parameters, the frequency equation of this serially isolatedsystem is derived, and the frequencies and mode shapes are obtained by thenumerical method. According to the Betti law, the orthogonal conditions ofmodes of this serially isolated system with concentrated and distributedparameters are deduced and the generalized mass and stiffness can beobtained. By decomposing the non-proportional damping of serially isolatedsystem to the parts of proportional damping and non-proportional damping,the damping ratio of the non-proportional damping in the equivalent mode isderived by Hamilton principle. Therefore the vibration equation of thenon-proportional damping of the isolated system is decoupled, and theresponses of structure under earthquake excitation can be solved by the modesuperposition method. A seismic response case of the 330\,kV voltagetransformer is analyzed by the semi-analytical solution and numericalintegration solution of FEM, suggesting that the serially isolated systemhas an obvious function of shock absorption. In addition, the systemresponses obtained with the two methods are basically consistent to indicatethe effectiveness of this serially isolated system and the correctness ofthis semi-analytical solution.
2009, 41(3): 440-448. doi: 10.6052/0459-1879-2009-3-2007-658