摘要:

AbstractThe arbitrary Lagrange–Euler (ALE) kinematic description has been implemented in a 3‐D transient finite element program so as to simulate multiple fluid flows with surfaces and interfaces of general shapes.The description of fluid interfaces includes continuity of velocity and a discontinuous tangential and normal stress appropriate for fluids of variable interfacial tension.The formulation is particularly relevant to the description of low and intermediate Reynolds number flow dominated by interfacial tens

ISSN:0029-5981    

DOI:10.1002/nme.1620380502

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe conjugate gradient method using two search step sizes is used to solve the inverse problem of simultaneously estimating the periodic thermal contact conductance,hc(t), and the heat transfer coefficient of the exhaust gases,hg(t), between the exhaust valve and seat in an internal combustion engine. The importance of the determination ofhc(t) andhg(t) lie in that they are the critical factors for designing the cooling system and the insulation of the exhaust valve.The inverse analysis is based on the temperature measurements taken from the sensors placed in both the valve and seat regions during the transient process of operation. In this study two unknown timewise‐varying functionshc(t) andhg(t) are to be estimated at the same time, thus two search step sizes with each one corresponding to each unknown function are derived. The results show that the CPU time for the inverse solutions using two search step sizes are greatly reduced than using just one search step size1for the determination of two unknowns, besides, it also shows that the inverse solutions are reliable even when the measurement errors are considered.The advantage of the conjugate gradient method is that noa prioriinformation is needed on the variation of the unknown quantities, since the solution automatically determines the functional form over the domain specified. The successful development of the present technique can be applied to any kind of two‐dimensional periodic contact problems, such as the determination of a two‐dimensional contact conductance problem2and the temperature or heat flux behaviour on the inside wall of internal combustion eng

ISSN:0029-5981    

DOI:10.1002/nme.1620380503

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper presents a cost‐effectiveness analysis of explicit Finite Difference (FD) methods for the numerical integration of the wave equation. Formal notions ofcomputational cost(expressed in floating point operations) and numericaldispersion errorare introduced. Restricting the analysis to leapfrog timemarching, for sake of simplicity, various spatial discrete differentiators are examined. For each scheme, by minimizing the cost at a given error threshold,a cost‐effective operating poin(time sampling rate and number of gridpoints per shortest wavelength) is obtained, which is remarkably different from the stability limit. Different schemes, each operated at its cost‐effective point, are then compared. High‐order dispersion‐bounded operators, in the sense of Holberg,1are found to be competitive with the Pseudo‐spectral (PS) method.New optimal schemes improving over the Holberg's spatial differentiators are introduced together with accurate expansions of the convolutional weights is terms of the design error threshold. It is also shown that the composition of two distinct Holberg's operators of consecutive orders, with opposite phase properties, minimizes dispersion and yields cost‐effective schemes.Numerical experiments illustrate the suitability of the new methods for large‐scale wave‐equation

ISSN:0029-5981    

DOI:10.1002/nme.1620380504

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractMethods fora posteriorierror estimation for finite element solutions are well established and widely used in engineering practice for linear boundary value problems. In contrast here we are concerned with finite elasticity and error estimation and adaptivity in this context. In the paper a brief outline of continuum theory of finite elasticity is first given. Using the residuals in the equilibrium conditions the discretization error of the finite element solution is estimated both locally and globally. The proposed error estimator is physically interpreted in the energy sense. We then present and discuss the convergence behaviour of the discretization error in uniformly and adaptively refined finite element sequences.

ISSN:0029-5981    

DOI:10.1002/nme.1620380505

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper presents a method for the non‐linear analysis of space structures subjected to static and cyclic loading. A bounding‐surface kinematic hardening plasticity model is used to simulate the hardening and hysteritic material behaviour. The model is used in conjunction with the lumped plasticity assumption coupled with the concept of a yield surface in force space. A hardening coefficient matrix which is a function of the plastic strain and the elastic stiffness matrix is introduced while the vectorial nature of the material memory parameters is maintained. This provides a smooth transition from the elastic to the plastic regime which simulates the hysteresis loops quite accurately. An updated Lagrangian formulation is used together with a predictor/corrector solution method. Several examples are presented to demonstrate the accuracy and efficiency of the met

ISSN:0029-5981    

DOI:10.1002/nme.1620380506

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this paper, we explore the possibility of applying the moment method to determine the electromagnetic field distributions inside three‐dimensional bounded non‐linear dielectric objects of arbitrary shapes. The moment method has usually been employed to solve linear scattering problems. We start with an integral equation formulation, and derive a non‐linear system of algebraic equations that allows us to obtain an approximate solution for the harmonic vector components of the electric field. Preliminary results of some numerical simulations are rep

ISSN:0029-5981    

DOI:10.1002/nme.1620380507

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA general and robust solution procedure for non‐linear finite element equations with limit points is developed. At each equilibrium iteration the magnitude of the load is adjusted such that the residual force is orthogonal to the current displacement increment from the last equilibrium state. The method implements the physical condition that the orthogonal residual force will neither increase nor decrease the magnitude of the current displacement increment vector. The orthogonality condition is formulated directly in terms of conjugate variables and therefore does not contain any scaling parameters. Passage of load and displacement limit points is discussed as well as the relation to line search, minimum residual, and are‐length methods. The method is illustrated by two examp

ISSN:0029-5981    

DOI:10.1002/nme.1620380508

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA three‐dimensional fully coupled creep elastoplastic damage model at finite strain for isotropic non‐linear material is developed. The model is based on the thermodynamics of an irreversible process and the internal state variable theory. A hyperelastic form of stress–strain constitutive relation in conjunction with the multiplicative decomposition of the deformation gradient into elastic and inelastic parts is employed. The pressure‐dependent plasticity with strain hardening and the damage model with two damage internal variables are particularly considered. The rounding of stress–strain curves appearing in cycling loading is reproduced by introduction of the creep mechanism into the model. A numerical integration procedure for the coupled constitutive equations with three hierarchical phases is proposed. A consistent tangent matrix with consideration of the fully coupled effects at finite strain is derived. Numerical examples are tested to demonstrate the capability and performance of the present model at lar

ISSN:0029-5981    

DOI:10.1002/nme.1620380509

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractIt is the purpose of this paper to construct a mathematical/computational model for the accretion of snow on rotating snow sleeves attached to conductor rods, and to consider some of the limitations in the use of the assumption of perfect cylindrical‐sleeve growth, as currently employed to provide estimates of snow‐loading intensity.For purposes of illustration, three rotating snow accretion regimes are considered, in which the direction of the airflow is always taken as perpendicular to the axis of the conductor rod. Firstly, a horizontal conductor rod is free to rotate and is initially bare. Rotation of the system (conductor rod and accreted snow) is initiated by snow torque, due to eccentric snow loading on the windward side of the conductor, and is driven by aerodynamic torque generated by the windflow past the evolving, rotating, asymmetrical sleeve growth. Secondly, a vertical conductor rod is free to rotate and the bare rod is given an initial small angular velocity; the rotation of the accreting system is then driven by aerodynamic torque alone. Thirdly, a horizontal rod is fixed and is initially covered by an annulus of snow, supported by a thin layer of (unfrozen) water existing between the conductor and the snow sleeve. In this case, the rotation of the snow sleeve is due to the combined snow and aerodynamic torques and is now retarded by the viscous torque due to the rotating thin film of water.Asymptotic solutions obtained for small accretion time supplement numerical results derived from the computational models. Numerical results on these rotating non‐periodic snow accretion regimes are presented as a function of the wind speed, snow precipitation rate and diameter of the conducto

ISSN:0029-5981    

DOI:10.1002/nme.1620380510

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:0029-5981    

DOI:10.1002/nme.1620380511

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY