M. Shimada¹, A. Hoitink¹, K. K. Tamma^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.104, No.2, pp. 133-158, 2015, DOI:10.3970/cmes.2015.104.133

Abstract To-date, with the exception of the Newmark method and the midpoint rule, most computational algorithms under the umbrella of LMS methods, which are predominantly employed in research and commercial software fail to properly evaluate acceleration computations accurately for conducting the numerical dynamic simulations. Indeed, this is not trivial and a sound theoretical basis of the fundamental underlying issues is described in detail. In this paper, we provide a resolution and point-out several noteworthy perspectives to address the proper evaluation of acceleration computations for structural dynamics applications with focus on the class of LMS methods as an illustration. More >

Letícia Fleck Fadel Miguel¹, Leandro Fleck Fadel Miguel², João Kaminski Jr.³

CMES-Computer Modeling in Engineering & Sciences, Vol.104, No.2, pp. 87-104, 2015, DOI:10.3970/cmes.2015.104.086

Abstract Since the half of the XX century, attention was given to the instability of structures under parametric excitation, especially under periodic loads. On the other hand, the instability of bars subjected to axial loads of impulsive type has been little studied, in spite of the practical importance of the topic. Thus, in Engineering Design it is frequently supposed, without tests or additional verifications, that an axial load of short duration can exceed the Euler critical load of the bar without inducing damage in the same.
Within this context, this paper proposes the use of the truss-like Discrete Element Method… More >

F.Z. Chen^1,2, H.F. Qiang¹, W.R. Gao¹

CMES-Computer Modeling in Engineering & Sciences, Vol.104, No.1, pp. 41-68, 2015, DOI:10.3970/cmes.2015.104.041

Abstract A coupled method describing gas-solid two-phase flow has been proposed to numerically study the bubble formation at a single orifice in gas-fluidized beds. Solid particles are traced with smoothed particle hydrodynamics, whereas gas phase is discretized by finite volume method. Drag force, gas pressure gradient, and volume fraction are used to couple the two methods. The effect of injection velocities, particle sizes, and particle densities on bubble growth is analyzed using the coupled method. The simulation results, obtained for two-dimensional geometries, include the shape and diameter size of a bubble as a function of time; such results are compared with… More >

J. Sladek^1,2, V. Sladek¹, E. Pan³, D.L. Young⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.99, No.4, pp. 273-296, 2014, DOI:10.3970/cmes.2014.099.273

Abstract This paper presents a dynamic analysis of an anti-plane crack in functionally graded piezoelectric semiconductors. General boundary conditions and sample geometry are allowed in the proposed formulation. The coupled governing partial differential equations (PDEs) for shear stresses, electric displacement field and current are satisfied in a local weak-form on small fictitious subdomains. The derived local integral equations involve one order lower derivatives than the original PDEs. All field quantities are approximated by the moving least-squares (MLS) scheme. After performing spatial integrations, we obtain a system of ordinary differential equations for the involved nodal unknowns. It is noted that the stresses… More >

Chein-Shan Liu¹

CMES-Computer Modeling in Engineering & Sciences, Vol.98, No.4, pp. 375-407, 2014, DOI:10.3970/cmes.2014.098.375

Abstract In this paper we study the nonlinear dynamical system x^·=f(x,t) from a newly developed theory, viewing the time-varying function of sign(||f||²||x||²− 2(f·x)²) = −sign(cos 2θ) as a key factor, where θ is the intersection angle between x and f. It together with sign(cos θ) can reveal the complexity of nonlinear Duffing oscillator and a quadratic ship rolling oscillator. The barcode is formed by plotting sign(||f||²||x||²− 2(f·x)²) with respect to time. We analyze the barcode to point out the bifurcation of subharmonic motions and the range of chaos in the parameter space. The bifurcation diagram obtained by plotting the percentage… More >

Jason F. Hammond¹, Elizabeth J. Stewart², John G. Younger³, Michael J.Solomon², David M. Bortz^4,5

CMES-Computer Modeling in Engineering & Sciences, Vol.98, No.3, pp. 295-340, 2014, DOI:10.32604/cmes.2014.098.295

Abstract The overall goal of this work is to develop a numerical simulation which correctly describes a bacterial biofilm fluid-structure interaction and separation process. In this, the first of a two-part effort, we fully develop a convergent scheme and provide numerical evidence for the method order as well as a full 3D separation simulation. We use an immersed boundary-based method (IBM) to model and simulate a biofilm with density and viscosity values different from than that of the surrounding fluid. The simulation also includes breakable springs connecting the bacteria in the biofilm which allows the inclusion of erosion and detachment into… More >

Qing Song Tu¹, Michelle Lee², Samuel Zhang², Shaofan Li¹

CMES-Computer Modeling in Engineering & Sciences, Vol.98, No.3, pp. 247-259, 2014, DOI:10.32604/cmes.2014.098.247

Abstract In this paper, we present molecular dynamics simulations of diffusion of Na⁺, K⁺, and Cl^- ions through the single-walled carbon nanotubes(SWCNTs) that are embedded into the membrane of cells in aqueous solutions. A simplified atomic cell model that considers bilayer membranes is employed to study the transportation of ions inside CNTs. The simulated results indicate that the diffusion properties of ions and selectivity of CNT with respect to ions are affected by biological complexity of the cell membrane. We have found that the ion diffusion only occurs in the CNTs with chirality higher than (8, 8), which is bigger than… More >

R.A. Regueiro^1,2, B. Zhang², S.L. Wozniak³

CMES-Computer Modeling in Engineering & Sciences, Vol.98, No.1, pp. 1-39, 2014, DOI:10.3970/cmes.2014.098.001

Abstract The paper presents three-dimensional, large deformation, coupled finite element analysis (FEA) of dynamic loading on soft biological tissues treated as biphasic (solid-fluid) porous media. An overview is presented of the biphasic solidfluid mixture theory at finite strain, including inertia terms. The solid skeleton is modeled as an isotropic, compressible, hyperelastic material. FEA simulations include: (1) compressive uniaxial strain loading on a column of lung parenchyma with either pore air or water fluid, (2) out-of-plane pressure loading on a thin slab of lung parenchyma with either pore air or water fluid, and (3) pressure loading on a 1/8th symmetry vertebral disc… More >

Mao Liu^1,2, Jiawei Xiang¹, Haifeng Gao¹, Yongying Jiang¹, Yuqing Zhou¹, Fengping Li¹

CMES-Computer Modeling in Engineering & Sciences, Vol.97, No.5, pp. 425-436, 2014, DOI:10.3970/cmes.2014.097.425

Abstract A wavelet finite element method (WFEM) is developed to analyze the dispersion relation for one-dimensional phononic crystals (1DPCs). In order to calculate the band gaps (BGs) of 1DPCs, the wavelet finite element model is constructed using a slender beam element based on B-spline wavelet on the interval (BSWI). Combining with the Bloch-Floquet theorem and ω(k) technique, the model will be simplified as a simple eigenproblem. The performance of the proposed method has been numerically verified by one numerical example. More >

J.R. Zabadal¹, B. Bodmann¹, V. G. Ribeiro², A. Silveira², S. Silveira²

CMES-Computer Modeling in Engineering & Sciences, Vol.103, No.4, pp. 215-227, 2014, DOI:10.3970/cmes.2014.103.215

Abstract This work presents a new analytical method to transform exact solutions of linear diffusion equations into exact ones for nonlinear advection-diffusion models. The proposed formulation, based on Bäcklund transformations, is employed to obtain velocity fields for the unsteady two-dimensional Helmholtz equation, starting from analytical solutions of a heat conduction type model. More >