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  • Open Access

    ARTICLE

    A Revision of Relaxed Steepest Descent Method from the Dynamics on an Invariant Manifold

    Chein-Shan Liu1

    CMES-Computer Modeling in Engineering & Sciences, Vol.80, No.1, pp. 57-86, 2011, DOI:10.3970/cmes.2011.080.057

    Abstract Based-on the ordinary differential equations defined on an invariant manifold, we propose a theoretical procedure to derive a Relaxed Steepest Descent Method (RSDM) for numerically solving an ill-posed system of linear equations when the data are polluted by random noise. The invariant manifold is defined in terms of a squared-residual-norm and a fictitious time-like variable, and in the final stage we can derive an iterative algorithm including a parameter, which is known as the relaxation parameter. Through a Hopf bifurcation, this parameter indeed plays a major role to switch the situation of slow convergence to a new situation with faster… More >

  • Open Access

    ARTICLE

    Atomistic Exploration of Deformation Properties of Copper Nanowires with Pre-Existing Defects

    H.F. Zhan, Y.T. Gu1

    CMES-Computer Modeling in Engineering & Sciences, Vol.80, No.1, pp. 23-56, 2011, DOI:10.3970/cmes.2011.080.023

    Abstract Based on the embedded atom method (EAM) and molecular dynamics (MD) method, in this paper, the tensile deformation properties of Cu nanowires (NWs) with different pre-existing defects, including single surface defects, surface bi-defects and single internal defects, are systematically studied. In-depth deformation mechanisms of NWs with pre-existing defects are also explored. It is found that Young's modulus is insensitive to different pre-existing defects, but yield strength shows an obvious decrease. Defects are observed influencing greatly on NWs' tensile deformation mechanisms, and playing a role of dislocation sources. Besides of the traditional deformation process dominated by the nucleation and propagation of… More >

  • Open Access

    ARTICLE

    A Numerical Technique Based on Integrated RBFs for the System Evolution in Molecular Dynamics

    N. Mai-Duy1, T. Tran-Cong1, N. Phan-Thien2

    CMES-Computer Modeling in Engineering & Sciences, Vol.79, No.3&4, pp. 223-236, 2011, DOI:10.3970/cmes.2011.079.223

    Abstract This paper presents a new numerical technique for solving the evolution equations in molecular dynamics (MD). The variation of the MD system is represented by radial-basis-function (RBF) equations which are constructed using integrated multiquadric basis functions and point collocation. The proposed technique requires the evaluation of forces once per time step. Several examples are given to demonstrate the attractiveness of the present implementation. More >

  • Open Access

    ARTICLE

    Simulation of Sloshing Effect on Vessel Motions by Using MPS (Moving Particle Simulation)

    K.S. Kim1, B.H. Lee2, M.H. Kim1, J.C. Park3

    CMES-Computer Modeling in Engineering & Sciences, Vol.79, No.3&4, pp. 201-222, 2011, DOI:10.3970/cmes.2011.079.201

    Abstract The coupling and interactions between vessel motion and inner-tank sloshing are investigated by a potential-CFD (Computational Fluid Dynamics) hybrid method in time domain. Potential-theory-based 3D diffraction/radiation panel program is used to obtain the hydrodynamic coefficients and wave forces for the simulation of vessel motion in time domain. The liquid sloshing in tanks is simulated in time domain by using the improved Moving Particle Simulation (PNU-MPS) method and it is validated through comparison against sloshing experiments. The calculated sloshing tank forces and moments are applied to the vessel-motion simulation as excitation forces and moments. The updated ship motion, which is influenced… More >

  • Open Access

    ARTICLE

    Wave Propagation in Unsaturated Poroelastic Media: Boundary Integral Formulation and Three-dimensional Fundamental Solution

    P. Maghoul1, B. Gatmiri1,2, D. Duhamel1

    CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.1, pp. 51-76, 2011, DOI:10.3970/cmes.2011.078.051

    Abstract This paper aims at obtaining boundary integral formulations as well as three dimensional(3D) fundamental solutions for unsaturated soils under dynamic loadings for the first time. The boundary integral equations are derived via the use of the weighted residuals method in a way that permits an easy discretization and implementation in a Boundary Element code. Also, the associated 3D fundamental solutions for such deformable porous medium are derived in Laplace transform domain using the method of Hérmander. The derived results are verified analytically by comparison with the previously introduced corresponding fundamental solutions in elastodynamic limiting case. These solutions can be used,… More >

  • Open Access

    ARTICLE

    Modified Algorithm for Surface Tension with Smoothed Particle Hydrodynamics and Its Applications

    H.F.Qiang1, F.Z.Chen1, W.R. Gao1

    CMES-Computer Modeling in Engineering & Sciences, Vol.77, No.3&4, pp. 239-262, 2011, DOI:10.3970/cmes.2011.077.239

    Abstract Based on smoothed particle hydrodynamics (SPH) method with surface tension proposed by Morris, this paper is intended to modify equations for surface tension by modifying normal and curvature with corrective smoothing particle method (CSPM). Compared with the continuum surface force (CSF) model for surface tension employed in the traditional SPH method, the accuracy in the present paper is much higher in terms of handling the problems with large deformation and surface tension. The reason is that in the traditional SPH method the deficiency of particles is near the boundary and sharp-angled areas, and it causes gross errors of curvature calculation.… More >

  • Open Access

    ARTICLE

    Application of An Atomistic Field Theory to Nano/Micro Materials Modeling and Simulation

    Xiaowei Zeng1

    CMES-Computer Modeling in Engineering & Sciences, Vol.74, No.3&4, pp. 183-202, 2011, DOI:10.3970/cmes.2011.074.183

    Abstract This paper presents an atomistic field theory and its application in modeling and simulation of nano/micro materials. Atomistic formulation and finite element implementation of the atomistic field theory is briefly introduced. Numerical simulations based on the field theory are performed to investigate the material behaviors of bcc iron at coarse-grained scale and we have obtained the mechanical strength and elastic modulus, which are in good agreement with results by first principles calculations. Also the nanoscale deformation and failure mechanism are revealed in bcc iron nanorods under simple tension. It is interesting to observe that under tensile loading, iron has gone… More >

  • Open Access

    ARTICLE

    Slow Rotation of an Axially Symmetric Particle about Its Axis of Revolution Normal to One or Two Plane Walls

    Yi W. Wan1, Huan J. Keh2

    CMES-Computer Modeling in Engineering & Sciences, Vol.74, No.2, pp. 109-138, 2011, DOI:10.3970/cmes.2011.074.109

    Abstract The steady rotation of an axially symmetric particle about its axis of revolution normal to two plane walls at an arbitrary position between them in a viscous fluid is studied theoretically in the limit of small Reynolds number. The fluid is allowed to slip at the surface of the particle. A method of distribution of a set of spherical singularities along the axis of revolution inside a prolate particle or on the fundamental disk within an oblate particle is used to find the general solution for the fluid velocity distribution that satisfies the boundary conditions at the confining walls and… More >

  • Open Access

    ARTICLE

    Calculation of a Deformable Membrane Airfoil in Hovering Flight

    D.M.S. Albuquerque1, J.M.C. Pereira1, J.C.F. Pereira1,2

    CMES-Computer Modeling in Engineering & Sciences, Vol.72, No.4, pp. 337-366, 2011, DOI:10.3970/cmes.2011.072.337

    Abstract A numerical study of fluid-structure interaction is presented for the analysis of viscous flow over a resonant membrane airfoil in hovering flight. A flexible membrane moving with a prescribed stroke period was naturally excited to enter into 1st, 2nd and 3rd mode of vibration according to the selected membrane tension. The Navier-Stokes equations were discretized on a moving body unstructured grid using the finite volume method. The instantaneous membrane position was predicted by the 1D unsteady membrane equation with input from the acting fluid flow forces. Following initial validation against reported rigid airfoils predictions, the model is applied to the… More >

  • Open Access

    ARTICLE

    A Nonlinear Dynamic Model for Periodic Motion of Slender Threadline Structures

    Jinling Long1,2, Bingang Xu1,3, Xiaoming Tao1

    CMES-Computer Modeling in Engineering & Sciences, Vol.72, No.4, pp. 273-298, 2011, DOI:10.3970/cmes.2011.072.273

    Abstract Moving slender threadline structures are widely used in various engineering fields. The dynamics of these systems is sometimes time dependent but in most cases follows a periodic pattern, and slender yarn motion in textile engineering is a typical problem of this category. In the present paper, we propose a nonlinear approach to model the dynamic behavior of slender threadline structures with a real example in the analysis of slender yarn motion in spinning. Moving boundary conditions of yarn are derived and a consequence of the perturbation analysis for the dimensionless governing equations provides the zero order approximate equation of motion… More >

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