EI、Scopus 收录

2010 Vol. 42, No. 2

Display Method:
An improvement of tsien's equation of state in high-temperature and high-pressure gases
Bo Zhao, Jiping Cui, Jing Fan
According to the general principle of molecular dynamicstheory and the Lennard-Jones Devonshire(LJD) liquid theory, H.S.Tsien givenan fundamental equation of state for gases at high temperatures andpressures. Tsien's EOS has physical foundation, high accuracy eqlicit temperature, and simple form. In this paper, we tested the applicability of LJD liquid theory inhigh-temperature and high-pressure gases by constant volume-temperaturemolecular dynamics, and obtained exact MD calculations for high temperatureand pressure gases EOS. Based on the MD exact numerical solution. TheAAD between theaso data and the improved Tsien's Eos cesults is less than 10%.in high density vesign.
2010, 42(2): 151-158. doi: 10.6052/0459-1879-2010-2-2009-029
Experimental research on complex eddy viscosity modeling of multi-scale coherent structures in wall turbulence
Aidong Guo, Nan Jiang
In the dynamics equation of coherent structures withperiodical phasic average, Reynolds stress term \tilde {r}_{ij} = -(\langle {u}'_i {u}'_j \rangle - \overline {{u}'_i {u}'_j } ) thatnoncoherent structures contributes to coherent structures, is taken into themodel, in which the velocity strain rate of coherent structures ismultiplied by a complex eddy viscosity coefficient, as follows:\tilde {r}_{ij} = \nu _T \Big[ \dfrac{\partial \tilde {u}_i }{\partial x_j} + \dfrac{\partial \tilde {u}_j }{\partial x_i } \Big] +\dfrac{1}{3}\delta _{ij} ( \tilde {r}_{kk} ) ,where \nu _T is a complex eddy viscosity coefficient.Eddy viscosity coefficient is defined to be a complex, supposing that thereexist phase difference between velocity strain rate of coherent structuresand the Reynolds stress.The phase relation has been experimentally measured between velocitydistortion \dfrac{\partial \tilde {u}}{\partial y} of multi-scales coherentstructures in turbulent boundary layer over smooth plate and the Reynoldsstress, \tilde {r}_{12} and analyzed in a close-circuit low-speed windtunnel based on the expression \tilde {r}_{12} = \nu _T \Big[\dfrac{\partial \tilde {u}}{\partial y} + \dfrac{\partial \tilde{v}}{\partial x} \Big]. Through the phase difference analysis betweenthe Reynolds stress and the velocity distortion of coherent structures inwall turbulence during the bursting process of coherent structures,conclusions can be drawn as following:Relaxation time in dynamic interaction between the turbulence of coherentstructures with macroscopical scale and movement distortion of coherentstructures can't be ignored. Hence, there exist phase difference betweenReynolds stress component that noncoherent structures contribute to coherentstructures and the velocity distortion of coherent structures. It is animportant factor that needs to be taken into account for eddy viscositymodeling theory for non-steady turbulence macrostructure.The above phase difference depends on not only the scale of coherentstructures, but also the detail of physical burst process of coherentstructures, such as eject and sweep. The phase of the Reynolds stress isposterior than that of velocity distortion of coherent structures inejecting process, while anterior in sweeping process. In addition, phasedifference between them does not vary with boundary normal positions inlogarithmic sublayer.
2010, 42(2): 159-168. doi: 10.6052/0459-1879-2010-2-2008-568
CFD based virtual flight simulation of square cross-section missile with control in longitudinal flight
Yang Tao, Zhaolin Fan, Jifei Wu
The simulation of virtual flight based on computationalfluid dynamics (CFD) is now becoming possible together with theincorporation of a controller with control surface commands and controlsurface deflections. This paper investigates CFD-based virtual flight for ageneric square cross-section missile configuration in longitudinal motions.The incorporation of the flight mechanics equations and a controller intothe CFD solver loop, a multi-block structured-grid scheme with both thecontrol surface deformations and the rigid motion of the aircraft, aredescribed. This study is helpful to a wider effort towards the simulation ofguide and navigation, and validates flight stability in nonlinearaerodynamics regions. The virtual flight simulation of square sectionmissile with control in longitudinal flight are presentedincluding holding angle of attack and prescribed maneuver about incidencedecreasing with required angle. The availability of the coupling method andthe trim arithmetic are proved in the virtual flight simulations through thetwo typical maneuver actions.
2010, 42(2): 169-176. doi: 10.6052/0459-1879-2010-2-2008-497
A coupled Eulerian-Lagrangian method based on level set and its applications
Zupeng Jia, Xijun Wei
In this paper a coupled Eulerian-Lagrangian method based on level set formulti-material compressible fluid flow involving large deformation ispresented. In the scheme, a Lagrangian method is used in the domain withsmall deformation while an Euler method is used in the domain with largedeformation. The interface is treated by a new level set method and theGhost Fluid method. Furthermore, an explicit compatible finite elementmethod is employed as the Lagrangian method. In this Lagrangian method, thefinite element method is used to discretize the fluid equations in terms ofthe framework of compatibility, an edge-centered artificial viscosity isused to capture shocks, and the subzonal perturbed pressure is used toresist spurious and unresolved grid motions. A vertex-centered finite volumemethod based on approximate Riemann solver is used as the Eulerian method.In this Eulerian method, an HLLC numerical flux adapted to various equationsof state are employed, a second order accuracy in space is achieved by usinga reconstruction of primitive variables based on WENO approach. An explicittwo-stage Runge-Kutta time-stepping scheme is used in discretization oftime. A new method to determine the signs of the level set function and anew technique to compute the velocities of the projection points of theGhost points on the interface are proposed. Numerical examples show theaccuracy as well as the robustness of the method.
2010, 42(2): 177-182. doi: 10.6052/0459-1879-2010-2-2008-308
Numerical simulation of airflow movement in human mouth-throat model during cyclic respiratory pattern
Xinxi Xu, Xiuguo Zhao, Shulin Tan, Yajun Liu, Zhenhai Gao
The method of CFD was used to study airflow movementcharacteristics in human mouth-throat model. We investigated the airflowpatterns in human mouth-throat model, and the effect of airflow movement onthe wall of the mouth-throat model and the aerosols deposition werediscussed. During the inhalation phase, the airflow separates gradually nearthe outer wall of the pharynx and near the outer wall for the upper part ofthe trachea downstream of the glottis with, and the features of theseparation zone appearing is gradually formed. During the exhalation phase,the high velocity zone is created near the outer wall of pharynx and nearthe outer wall of the larynx. During the cyclic respiratory pattern, thehigh axial velocity zone and secondary flow are generated intermittently,eventually to induce the intermittent appearance of the high shearingstrength stress zone appears intermittently. The direction of the shearstress acting on the wall vary varies periodically, which not onlyresult in the increase of the probability of the wall strain and tissueinjury, but also lead to aerosol deposition easily in these areas at thesame time.
2010, 42(2): 183-190. doi: 10.6052/0459-1879-2010-2-2008-482
On three-dimensional numerical simulation of interstitial fluid flow of inter osseous membrane
Wei Yao, Yeliang Shen, Guanghong Ding
Interstitial fluid flow is an important component of themicrocirculation and interstitial environment, yet there is few direct invivo measurement of it within human body. Therefore, computational andmathematical models are employed to investigate the fluid flow especiallywithin cortical bone and ligaments.This article is to investigate the interstitial fluid flow in inter osseousmembrane on lower limb, where the distribution of capillaries is regularparallel arrays on certain direction which is approximate to the directionof parallel collagen fibrils. It' rational to consider the interstitialspace as a porous media and set up a three dimensional filtration model tostudy the flow field. The govern equations of the model is Brinkman equationand conservative equation. A CFD software (FLUENT) is used to executive thenumerical simulation.There are some interesting results. First, interstitial fluid penetratingthrough capillary' walls at artery sections can flow along the direction ofparallel capillaries, and then some interstitial fluid is absorbed bycapillary at vein sections and others outflow at the exit. That is, underparallel capillary distribution condition, there may exit the directionalinterstitial fluid flow. Second, the interstitial fluid flow can beevidently influenced by collagen fibrils. Due to the existence of collagenfibrils in the interstitial space, the velocity distribution of theinterstitial fluid flow tends to be uniform, which is in favor of thephysiological activities of cells. So collagen fibrils are very important tothe organism. Third, pressure is also an important factor to influence theinterstitial fluid flow. The increases of pressure near artery ($p_{a})$ andpressure near vein ($p_{v})$ can both accelerate the interstitial fluid flow,while increase of pressure in interstitial space ($p_{i})$ can decelerate theinterstitial fluid flow. Therefore, changing the pressure in capillaries canadjust the microenvironment which cells live in. Changing the pressure ininterstitial space has more effective effect than pressure changing incapillaries. As we all know, when the tissue is undergone the externalforce, the pressure in the interstitial space will be changed, so theinterstitial fluid flow will also be changed. It may be a potential reasonthat naprapathy has a curative effect on the microcirculation in tissues.
2010, 42(2): 191-196. doi: 10.6052/0459-1879-2010-2-2008-587
Fluid-structure interactional numerical simulation of erosion-corrosion failure of reducer in multiphase flow
Guofu Ou, Jie Qiu, Zuchao Zhu, Yanping Wang, Genfu Xu
In order to research the failure of reducer, we focusedon the protective corrosion product film formed on the wall of reducer andinvestigated the mechanism of erosion-corrosion damage caused by interactionof corrosion and fluid. The mathematical model of fluid-structureinteraction was established. N-S equation of viscosity liquid and controlequation of solid area of corrosion products are postulated with ArbitraryLagrange-Euler (ALE). The interaction between multiphase liquid in boundarylayer within pipe wall and the damage of protective erodent products film isanalyzed. Applying with the Femlab software, the deformation of protectiveerodent products film in three different ways were analyzed, includingdifferent flows in reducer, different structures of reducer and differentspecifications of reducer. The numerical simulation result indicatedthat the deformation of protective erodent products film is relativelysmall, when the following conditions are satisfied, such as the fluid flowsfrom the small inlet to large outlet, the concentric reducer and therelatively small difference of two end calibers of reducer. The obtainedresults can be used in erosion protecting and technical modification for thereducer.
2010, 42(2): 197-204. doi: 10.6052/0459-1879-2010-2-2008-693
The study on the sedimentation of solid particle influenced by thermal convection using direct numerical simulation
Jianzhong Chang, Kang An, Hantao Liu
Based on the study of isothermal inert particlesedimentation, the Arbitrary Lagrangian-Eulerian technique was used to solvethe problem of solid particle sedimentation with thermal convectionincluding the energy equation, according to varying the solid-fluid densityratio, that is, the particles settle in different Reynolds number. Theresults show that the thermal convection induces the variety of flow fieldand asymmetry. While setting in hot fluid, the direction of thermalconvection is the same as that of particle sedimentation, and there arevortex shedding arisen by thermal convection. During the sedimentation ofhot particle in the cold fluid, the warm wake forms a strong upward thermalplume. With the increasing of Reynolds, the setting particles undergo threestages: steady motion with and without overshoot; weak and strongoscillations, and irregular oscillations.
2010, 42(2): 205-211. doi: 10.6052/0459-1879-2010-2-2008-649
Studying on the penetration depth of penetrator with including the effect of mass abrasion
Jun Zhao, Xiaowei Chen, Fengnian Jin, Ying Xu
Mass abrasion is observed on the nose of a projectilewhen it strikes concrete target at high velocity, which significantly affectthe penetration performance. To evaluate the influence of the mass abrasionon the depth of penetration (DOP), an empirical relationship between thenose factor of the residual projectile after abrasion and the initial impactvelocity is constructed according to the published experimental data. Basedon the dynamic cavity expansion theory, considering the varying nose shapeand the instant mass of a projectile, a modified model is proposed tocalculate the DOP of kinetic energy penetrator. The modified modeldemonstrates that an upper limit of DOP exists due to the mass abrasion ofprojectile, which also had been confirmed by different experimental data.
2010, 42(2): 212-218. doi: 10.6052/0459-1879-2010-2-2009-009
Boundary layer effect and thin body structure in bem for potential problems
Yaoming Zhang, Yan Gu, Jeng-Tzong Chen
In boundary element analyses, when a considered fieldpoint is very close to an integral element, the kernels' integration wouldexist various levels of near singularity, which can not be computedaccurately with the standard Gaussian quadrature. As a result, the numericalresults of field variables and their derivatives may become lesssatisfactory or even out of true. This is so-called ``boundary layereffect''. Therefore, the accurate evaluation of nearly singular integralsplays an essential role to obtain highly accurate and reliable results byusing boundary element method (BEM). For most of the current numericalmethods, especially for the exact integration method, the geometry of theboundary element is often depicted by using linear shape functions whennearly singular integrals need to be calculated. However, most engineeringprocesses occur mostly in complex geometrical domains, and obviously, higherorder geometry elements are expected to be more accurate to solve suchpractical problems. Thus, efficient approaches for estimating nearlysingular integrals with high order geometry elements are necessary both intheory and application, and need to be further investigated. As is wellknown, for high order geometry elements, the forms of Jacobian andintegrands are all complex irrational functions, and thus for a long time,the exact evaluation of nearly singular integrals is a difficult problem oreven impossible implementation. In this paper, a new exact integrationmethod for element integrals with the curvilinear geometry is presented. Thepresent method can greatly improve the accuracy of numerical results ofnearly singular integrals without increasing other computational efforts.Numerical examples of potential problems with curved elements demonstratethat the present algorithm can effectively handle nearly singular integralsoccurring in boundary layer effect and thin body problems in BEM.
2010, 42(2): 219-227. doi: 10.6052/0459-1879-2010-2-2009-079
n the fourth order tensor valued function of the stress in return map algorithm
Mingxiang Chen
The inversion of a fourth order tensor valued functionof the stress and its transformation to the second order tensor are requiredin the return map algorithm for implicit integration of the constitutiveequation. Based on a set of the base tensors which are mutually orthogonal,this paper presents an effective methodology to perform those tensoroperations for the isotropic constitutive equations. In the scheme, two ofthe base tensors are the second order identity tensor and the deviatoricstress tensor, respectively. Another base tensor is constructed using anisotropic second order tensor valued function of the stress. The three basetensors are coaxial. By making use of the representation theorem forisotropic tensorial functions, all the second order, the fourth order tensorvalued functions of the stress involved can be represented in terms of thebase tensors. It shows that the operations between the tensors are specifiedby the simple relations between the corresponding matrices. The inversion ofa fourth order tensor is reduced to the inversion of corresponding 3\times3 matrix, and its transformation to the second tensor is equivalent totransformation of 3\times 3 matrix to 3\times 1 column matrix. Finally,some discussions are given to the application of those transformationrelationships to the iteration algorithm for the integration of theconstitutive equations.
2010, 42(2): 228-238. doi: 10.6052/0459-1879-2010-2-2009-016
Material design of permeability coefficient based on adaptive mesh
Shengli Xu, Gengdong Cheng
Finite element mesh size has considerable effect on theresult of optimum design when the topology optimization method based ondesign variable of element (node) is used to design structure and material.The cell should be divided into very small size grids for no-slip boundarycondition at fluid-solid interface in microstructure design of materialpermeability. Material microstructure design with inverse homogenizationmethod based on adaptive mesh is studied in this paper. The objectivefunction is maximizing isotropic permeability coefficient. The finiteelement mesh near fluid-solid interface will be refined adaptively duringoptimization iteration process for decreasing computing scale ofoptimization problem. With this algorithm, the material microstructure isobtained to be uniform from different initial density distributions. Theresult illustrates the effectiveness of our method.
2010, 42(2): 238-244. doi: 10.6052/0459-1879-2010-2-2008-730
Multi-objective optimization for sheet metal formnig of drawing with successive response surface method
Guangyong Sun, Guangyao Li, Gang Zheng, Zhihui Gong
This paper describes a multi-objective optimization ofdrawbead geometrical parameters of automotive panel using successiveresponse surface method. The existing response surface method has a lowprecision in the entire design space, and conventional single-objectiveoptimization design does not provide for multi-objective conditions and hasbeen used to optimize only a single objective. The present method updatesthe region of interest (ROI) in the design space by panning and zooming. Ineach ROI, a set of pareto optimal solutions of equivalent drawbead restraintforce,are obtained to minimize the defects of crack and wrinkle by combiningdesign of experiments, successive response surface method andmulti-objective particle swarm optimization. Through the minimum distancemethod, a solution with best forming approach is obtained from the paretooptimal solutions, and it is used as the center point of the next region ofinterest. The optimal drawbead restraint force will be obtained by theiterative procedure. The optimal design geometric parameters of drawbead canbe obtained using the optimal drawbead restraint force and geneticalgorithm. These optimal parameters can be efficiently used to improve theforming properties of sheet. Numerical examples indicate that the presentmethod has higher precision and practicability compared with the existingtechniques.
2010, 42(2): 245-255. doi: 10.6052/0459-1879-2010-2-2007-532
A new structural topological optimization method based on design space adjustments
Jianhua Rong, Qiang Zhang, Sen Ge, Rangke Mu
Although a discrete solid and void structural topology is typicallydesired, a continuous material density design field is usually assignedto the material points within the design domain to spatially indicateregions of solid and void material. The solid isotropic microstructurewith penalization material (SIMP) formulation is easy to implement in afinite element (FEM) framework. However, the material in those regions,where the values of density variables are between 0 and 1,is artificial. It is necessary to deal with those regions after theoptimum topological configuration is obtained. Then a new constraint,labeled the sum of the reciprocal variables (SRV), for 0/1topological design was introduced to obtain 0/1 topology solutions.The structuraldesign domain need be divided into some finite element mesh when structuraltopology optimization is made. Some optimization problems may need a largefinite element mesh, the authors propose a new structural topologicaloptimization method based on design space adjustments in order to solvingthis problem and obtaining 0$/$1 topology solutions. In topology optimization,a design space is specified by the number of design variables, and theirlayout or configuration. The proposed procedure has one efficient algorithmfor adjusting design space. First, the rational approximation for materialproperties (RAMP) is adopted to design the topology structural stiffnessmatrix filter function, and the design space can be adjusted in terms ofdesign space expansion and reduction. This capability is automatic when thedesign domain needs expansion or reduction, and it will not affect theproperty of mathematical programming method convergences. Second, to get aclearer topological configuration at each iteration step, by introducing thediscrete condition of topological variables, integrating with the originalobjective and introducing varying displacement constraint limitmeasurements, optimal series models with multi-constraints is formulated tomake the topological variables approach 0 or 1 as near as possible. Third, aheuristic algorithm is given to make the topology of the design structure beof solid/empty property and get the optimum topology during the secondoptimization adjustment phase. Finally, incorporating an incompletesecond-order series expansion for structural displacements, a new continuumstructural topological optimization method is proposed. The computationalefficiency is enhanced through the size reduction of optimization structuralfinite model and the adoption of the displacement iterative solving methodduring two optimization adjustment phases. The three simulation examplesshow that the proposed method is robust and practicable.
2010, 42(2): 256-267. doi: 10.6052/0459-1879-2010-2-2008-766
Concurrent hierarchical optimization for structures composed of modules considering size effects
Jun Yan, Ling Liu, Xiaofeng Liu, Jiadong Deng
The concurrent optimization model and algorithm formodular structures are developed in this paper. The effects of actual sizeof the basic design module on optimization results are investigated for structures composed of periodic modules. The size of modules can greatlyaffect the optimization results of configuration and distribution of basicdesign modules. The concurrent optimizations of macro structures and designmodules are implemented by introducing independent densities inmacro-structure and micro-module hierarchies as design variables. Theoptimal designs of configurations of macro structure and modules in twohierarchies are obtained via topology optimization and penalty technique.The interactions of structures and modules can be considered automaticallyby the optimization model. Two numerical examples with single load and multiloads are presented to validate the proposed optimization model andalgorithm.
2010, 42(2): 268-274. doi: 10.6052/0459-1879-2010-2-2008-694
The occurrence conditions and trajectory constructions for low energy cislunar transfers
Ming Xu
The paper deals with the occurrence conditions andtrajectory constructions for low-energy transfers in the cislunar space,from the views of libration point theories and nonlinear dynamicaltechniques. The classical concept of ``libration'' is unavailable forspatial bicircular model (SBCM) because of the time-dependent perturbations.So the equivalent equilibrium is defined according to the geometry ofinstantaneous Hill's boundary, i.e., LL_{1} or LL_{2}. The altitudes ofperiapsis and eccentricities of all the lunar capture trajectories arepresented via the Poincare map, and the minimum energy to capture on thelunar surface is deduced which is quite different from ones obtained incircular restricted three-body problem (CR3BP) and Hill Models. Theasymptotical behaviors of invariant manifolds flown from libration point orHalo orbit are destroyed by SBCM: the durations flown in and out of thelibration point or Halo orbit have shifted from infinite to finite, and thedirections have changed from reversible to nonreversing. The minimum energycislunar transfer is acquired by the trajectory transiting LL_{1} point,and the (M,N)- loopy transiting trajectories are attained by transitingLL_{1}-Halo orbits. Similarly, the minimum energy of weak stabilityboundary (WSB) transfer is induced by the trajectory transitingLL_{2} point, and the earth's escape and lunar capture windows for WSBtransfers are yielded by transiting LL_{2}-Halo orbits. All threetransfer manners, as low-thrust,impulse and WSB, are applied to the transfer from Earth to Moon and theinsertion of the distant retrograde orbit (DRO).
2010, 42(2): 275-289. doi: 10.6052/0459-1879-2010-2-2008-708
ode localization prediction criterion for T-tail structure
Zhichun Yang
Mode localization is often an unexpected dynamicphenomenon in weakly-coupled symmetric structure, and it arises from smallimperfections (less than 5{\%}) which perturb the symmetry. Suchimperfections typically result from random manufacturing or assemblyimprecision. Mode localization prediction is an important problem in T-Tailstructure design because some drastic localized vibration phenomena occurduring ground vibration test of T-Tail aircraft. Mode localization isdependent not only on mistuning, but also on coupling intensity. In thispaper, we define the degree of mode localization with the peak amplituderatio and the coupling intensity with stiffness ratio of horizontalstabilizer to fin in T-Tail structure. The influence of mass mistuning onmode localization and frequency loci veering of T-Tail structure is studied.Based on the mass mistuning model, four different criterions are proposed topredict the occurrence of mode localization in T-Tail structure from fourview points, which are the peak amplitude ratio, coupling mistuned ratio,ordinary eigenvalue perturbation method and eigenvalue perturbation methodfor nearly equal frequencies, respectively. The numerical simulation resultsfor a T-Tail structure model indicate that mode localization is most likelyto occur in T-Tail structure consisting of weakly coupledsubstructures---horizontal stabilizer and fin. Moreover, when localizationoccurs, the first two bending vibration modes in T-Tail structure are proneto localization, and only one of the two mode frequencies is changed byparameter mistuning to induce frequency loci veering phenomena. The resultsof this study also demonstrate the feasibility and effectiveness of theproposed four predicting criterions of mode localization, and thus provide areference solution to the prediction and design of mode localization of thiskind structure.
2010, 42(2): 290-299. doi: 10.6052/0459-1879-2010-2-2008-588
The quasi-variational principles of rigid-body dynamics and their applications
Lifu Liang, Qingyong Guo
The Reference [1] points out that recent studies to solvethe problems of flexible multi-body dynamics mainly depend on the numerical,quantitative methods and almost no one involves in the analytical discussiondue to the complexity of flexible multi-body configuration. It isunfavorable to profoundly understand the essence of nonlinear mechanics ofthe system and to predict the feature of overall dynamics of the system.Therefore, it is the need to study theoretical analysis of flexiblemulti-body system. Of course, this is a very complex problem and it takes avery long time to solve this problem. The research of this papercarries out to adapt this need.For flexible multi-body, if we think that external forces on the deformablebody (including body force and surface force) are non-conservative forces,which also lead to non-conservative forces on the rigid body, that is, theresultant force and the resultant couple acting on center of mass arenon-conservative generalized forces. This research is to apply thequasi-variational principles of non-conservative system to the theoreticalanalysis of the flexible multi-body dynamics. Because of the complexity ofthe problem, it is divided into several sub-tasks: 1. To study thequasi-variational principles of rigid-body dynamics and their applications.This is the main subject of this paper; 2. To study the quasi-variationalprinciples of flexible single-body dynamics and their applications. Thissubject has been published in ``Science in China''; 3. To study the quasi-variational principles of flexible multi-body dynamics and theirapplications. This subject has been written in Ph.D. thesis.In this paper, the quasi-variational principles of rigid-body dynamics areestablished. The quasi-stationary conditions of the quasi-variationalprinciples of rigid-body dynamics are deduced. The generalizedquasi-variational principles of rigid-body dynamics are established. Theapproach to seek analytical solution and numerical solution of rigid-bodydynamics is illuminated by using generalized quasi-variational principles.Finally, the advantage of applying variational methods to the study of therigid-body dynamics is validated by calculation examples.
2010, 42(2): 300-305. doi: 10.6052/0459-1879-2010-2-2008-637
Asymptotic solution of thermocapillary convection of thin two-layer system in an annular cavity
Yourong Li, Shuangcheng Wang, Wanyuan Shi, Shuangying Wu
The convection phenomena in two-layer liquid systems haveattracted great attention in the past two decades, mainly owing to theirrelevance in nature and in many engineering applications. Many works havebeen carried out to investigate the thermocapillary convection in two-layerliquid systems in rectangular cavities or in infinite horizontal layers.However, few studies focused on the convection phenomena in two-layer liquidsystems in the annular cavity. In order to understand the basiccharacteristics of thermocapillary convection of the thin two superposedhorizontal liquid layers subjected to a radial temperature gradient in anannular cavity, an approximate analytical solution is obtained usingasymptotical analysis. The cavity is heated from the outer cylindrical walland cooled at the inner wall. Bottom and top surfaces are adiabatic. Resultsshow that the expressions of velocity and temperature field in the coreregion are the same as the results obtained by Nepomnyashchy et al (Physicsof Fluids, 2006, 18: 032105) when thin annular pool approaches to thin two-dimensional slot.The numerical experiments are also carried out to compare with theasymptotic solution. It is found that there is a good agreement between theasymptotic solution and numerical result in the core region.
2010, 42(2): 306-311. doi: 10.6052/0459-1879-2010-2-2008-751
Experimental study on the characteristics of ctac solution flow in the rectangular channel
Weiguo Gu, Dezhong Wang, Yasuo Kawaguchi, Hongxia Zhang
In the dilute surfactant drag-reducing flow, the slight viscoelasticity ofsolution affects the energy dissipation process of the flow, and this flowexhibits special fashion different from laminar flow or turbulent one inNewtonian fluid. The study on the modification of turbulent structures bythe viscoelasticity of the solution is important to clarify the dragreduction mechanism of surfactant solution flow. In this paper, dragreducing flow of dilute surfactant solution in the two dimensional rectanglechannel has been investigated experimentally. To grasp the instantaneousvelocity u-v in x-y plane, particle image velocimetry (PIV) is employed. Theexperiments pay attention to Reynolds number ranging from 10000 to40000 and concentration of additive CTAC (a kind of cationicsurfactants) from 25 to 100ppm on the flow.As for the additive CTAC concentration of 25, 40, 60 and 100ppm, the fanningfriction factor decreases and drag reduction (DR) increases with theincrease of mass concentration below the critical Reynolds number. Thesurfactant solution with 40ppm at Re=40000, compared with waterflow, shows DR of more than 70%.The instantaneous distribution of velocity, vorticity, and correlation ofvelocity fluctuation is analyzed. Statistics calculation is carried outbased on 500 velocity fields which are measured by PIV. The results exhibitthat the drag-reducing flow shows the approximate characteristics of thelaminar flow. The wall-normal velocity fluctuation of drag-reducing flow isdamped, which causes the decrease of turbulence transportation and Reynoldsshear stress comparing with the turbulent water flow. The streamwisevelocity fluctuation of drag-reducing flow shows the streamwise developedband-like distribution. This pattern indicates the new characteristic ofturbulence transportation in drag-reducing flow.
2010, 42(2): 312-318. doi: 10.6052/0459-1879-2010-2-2008-444
An optimal algorithm of the generalized jacobi method
Fengqiang Shen
An optimal algorithm of the generalized Jacobi method is developed to solvethe generalized eigen-problems in the finite element analysis of structuralproblems. Novel operations in this optimal algorithm are adopted to definethe threshold estimation for the off-diagonal elements and the convergencycriteria in the sweeping iterations, so that the present algorithm isapplicable to the original structural problems, not only with thepositive-definite matrices, but also with the general symmetric matrices solong as their eigenvalues are all real numbers. This paper has proved theoptimal algorithm mathematically.
2010, 42(2): 319-324. doi: 10.6052/0459-1879-2010-2-2008-043
Three-dimensional analysis for static bending and free vibration of functionally graded rectangular plate
Fengxi Zhou, Shirong Li
The state equation of functionally graded rectangularplate were established with the state variables of three displacementcomponents and three stress components, based on the three-dimensionallinear elastic theory by using of state space method. Considering simplysupported boundary conditions, the static bending and free vibrationproblems of a three-dimensional functionally graded rectangular plate werenumerically solved by shooting method with that the material propertiesthrough the thickness coordinate are assumed to obey the exponent lawdependence. Effects of the volume fraction distributions of constituentmaterials, and thickness-to-side ratio of functionally graded rectangularplate on the dynamical and static responses were studied. The presentalgorithm can be used to research the three-dimensional elastic response offunctionally graded materials.
2010, 42(2): 325-331. doi: 10.6052/0459-1879-2010-2-2007-576
Nonlinearity system identification method with parametric excitation based on the incremental harmonic balance method
Suguang Dou, Min Ye, Wei Zhang
In this paper, the incremental harmonic balance for nonlinearityidentification (IHBNID) is presented for the modeling and parametricidentification of nonlinear systems. The effects of harmonic balancenonlinearity identification (HBNID) and IHBNID are also studied and comparedby using the numerical simulation. Considering the Mathieu-Duffing equationas an example, the effectiveness of the IHBNID can be verified. With the aidof the new method, the derivation procedures of the incremental harmonicbalance method are simplified. The results show that the IHBNID is highlyefficient for computation, and its performances excel in those of the HBNID,such as the computation accuracy and the noise resistance.
2010, 42(2): 332-336. doi: 10.6052/0459-1879-2010-2-2008-770
Reachable domain of a satellite with a coplanar impulse applied
Dan Xue, Junfeng Li, Fanghua Jiang
This paper studies the reachable domain of a satelliteafter a coplanar single impulse with fixed magnitude applied. On theassumption that all of the generated trajectories are ellipses due to thesmall amplitude impulse, the reachable domain is bounded. According to thedefinition of the envelope of the curve family in a plane, the boundary ofreachable domain is revealed respectively for three situations, namely, thepoint to apply impulse is fixed and the direction is arbitrary, the point toapply impulse is arbitrary and the direction is fixed, both the point toapply impulse and the direction are arbitrary. The simulation resultsverify the validity of the present approach.The conclusion has no restriction on theeccentricity of the initial elliptic orbit, and fits for the situation ofinitial elliptic orbit with large eccentricity.
2010, 42(2): 337-342. doi: 10.6052/0459-1879-2010-2-2008-772