Ma Tianbao¹, Wang Cheng, Ning Jianguo

CMES-Computer Modeling in Engineering & Sciences, Vol.33, No.2, pp. 155-178, 2008, DOI:10.3970/cmes.2008.033.155

Abstract A multi-material Eulerian hydrodynamic numerical method and hydrocode that can effectively simulate explosion problems in engineering practice were developed in this study. A modified Youngs' interface reconstruction algorithm was proposed for mixed cells, in which the material's volume fractions of the surrounding cells are not only used to reconstruct the material interface but also adopted to determine the transport order of the material. The algorithm developed herein was validated by the modeling of several tests, such as objects with different shapes moving in translational, rotating and shear flow field in two dimensional Descartes coordinates and axis-symmetric cylindrical coordinates. Results show… More >

Patrícia C.T. Gonçalves^1,2, João Manuel R.S. Tavares^1,2, R.M. Natal Jorge^1,3

CMES-Computer Modeling in Engineering & Sciences, Vol.32, No.1, pp. 45-56, 2008, DOI:10.3970/cmes.2008.032.045

Abstract The main goals of the present work are to automatically extract the contour of an object and to simulate its deformation using a physical approach. In this work, to segment an object represented in an image, an initial contour is manually defined for it that will then automatically evolve until it reaches the border of the desired object. In this approach, the contour is modelled by a physical formulation using the finite element method, and its temporal evolution to the desired final contour is driven by internal and external forces. The internal forces are defined by the intrinsic characteristics of… More >

T.Z. Desta¹, G. De Bruyne¹, J.-M. Aerts¹, M. Baelmans², D. Berckmans¹

CMES-Computer Modeling in Engineering & Sciences, Vol.31, No.2, pp. 61-70, 2008, DOI:10.3970/cmes.2008.031.061

Abstract This paper demonstrates the use of the concept of the local mean age of air (LMAA) to quantify ventilation effectiveness under bicycle rider's safety helmets. The specific objective is to study the effect of helmet openings on the resulting ventilation effectiveness. To quantify ventilation effectiveness using the concept of LMAA, dynamic tracer gas data are necessary. The data were generated using a Computational Fluid Dynamics (CFD) model. Two bicycle helmet designs were used and compared with respect to ventilation performance. The result showed that the helmet with more openings had better performance especially at the back of the head. The… More >

Shih-Kai Chien¹, Tzu-Hsiang Yen¹, Yue-Tzu Yang¹, Chao-Kuang Chen^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.29, No.3, pp. 163-174, 2008, DOI:10.3970/cmes.2008.029.163

Abstract Conventional proton exchange membrane fuel cells (PEMFCs) have a straight gas flow serpentine channel, and hence the reactant gases are transferred to the catalyst layers as a result of diffusion alone. Since the diffusion process is inherently slow, the electrical performance of such PEMFCs is inevitably limited. In an attempt to improve the PEMFC performance, this study replaces the straight channel with containing different type of obstacles and conducts a series of lattice Boltzmann method simulations to investigate the flow field phenomena induced in a viscous liquid as it flows along the serpentine channel at Reynolds numbers ranging from Re=5~25.… More >

H. T. Wang¹, Z. H. Yao²

CMES-Computer Modeling in Engineering & Sciences, Vol.29, No.1, pp. 1-14, 2008, DOI:10.3970/cmes.2008.029.001

Abstract Carbon nanotubes (CNTs) may provide ultimate enhancement in stiffness and strength for composite materials. This paper presents a rigid-fiber-based boundary integral equation formulation for the numerical simulation of debonding process and the corresponding strength of CNT reinforced composites. The CNT/matrix interfaces are assumed to fail when the interfacial shear force reaches a prescribed threshold, and the CNTs and matrix are considered to be detached in the failed areas. The matrix with one or several tens of originally well-bonded CNTs is subjected to an incremental tensile load and the effective stress-strain relations are readily obtained by the introduction of CNT/matrix debonding… More >

N.Kringos¹, A.Scarpas¹, A.P.S. Selvadurai²

CMES-Computer Modeling in Engineering & Sciences, Vol.28, No.3, pp. 147-160, 2008, DOI:10.3970/cmes.2008.028.147

Abstract This paper presents a numerical approach for the modeling of water flow induced mastic erosion from a permeable asphalt mix and is part of an ongoing effort to model moisture-induced damage in asphalt mixes. Due to the complex composite structure of asphalt mixtures, moisture can infiltrate in various ways into the components and have an adverse effect on its mechanical performance. Depending on the gradation of the asphalt aggregates and the mixing procedure, asphalt structures with a variable permeability may result. Open-graded asphalt mixes are designed with a high interconnected air void content to serve as a drainage layer on… More >

Chun Yang¹, Dalin Tang², Chun Yuan³, William Kerwin², Fei Liu³, Gador Canton³, Thomas S. Hatsukami^3,4, Satya Atluri⁵

CMES-Computer Modeling in Engineering & Sciences, Vol.28, No.2, pp. 95-108, 2008, DOI:10.3970/cmes.2008.028.095

Abstract Atherosclerotic plaque rupture and progression have been the focus of intensive investigations in recent years. Plaque rupture is closely related to most severe cardiovascular syndromes such as heart attack and stroke. A computational procedure based on meshless generalized finite difference (MGFD) method and serial magnetic resonance imaging (MRI) data was introduced to quantify patient-specific carotid atherosclerotic plaque growth functions and simulate plaque progression. Participating patients were scanned three times (T₁,T₂, and T₃, at intervals of about 18 months) to obtain plaque progression data. Vessel wall thickness (WT) changes were used as the measure for plaque progression. Since there was insufficient… More >

B Radhika¹, S S P,a¹, C S Manohar^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.27, No.1&2, pp. 79-110, 2008, DOI:10.3970/cmes.2008.027.079

Abstract Reliability of nonlinear vibrating systems under stochastic excitations is investigated using a two-stage Monte Carlo simulation strategy. For systems with white noise excitation, the governing equations of motion are interpreted as a set of Ito stochastic differential equations. It is assumed that the probability distribution of the maximum in the steady state response belongs to the basin of attraction of one of the classical asymptotic extreme value distributions. The first stage of the solution strategy consists of selection of the form of the extreme value distribution based on hypothesis tests, and the next stage involves the estimation of parameters of… More >

Wenzhong Tang¹, Suresh G. Advani¹

CMES-Computer Modeling in Engineering & Sciences, Vol.25, No.3, pp. 149-164, 2008, DOI:10.3970/cmes.2008.025.149

Abstract In this paper, a method for studying nanotube dynamics in simple shear flow was developed. A nanotube was described as a flexible fiber with a sphere-chain model. The forces on the nanotube were obtained by molecular dynamics simulations. The motion of the nanotube in simple shear flow was tracked by the flexible fiber dynamics method [Tang and Advani (2005)]. The viscosity of dilute nanotube suspensions was calculated based on the nanotube dynamics, and the effects of the aspect ratio and initial curvature of the nanotube on suspension viscosity are explored and discussed. More >

C. Moulinec¹, R. Issa², J.-C. Marongiu³, D. Violeau⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.25, No.3, pp. 133-148, 2008, DOI:10.3970/cmes.2008.025.133

Abstract The gridless Smoothed Particle Hydrodynamics (SPH) numerical method is preferably used in Computational Fluid Dynamics (CFD) to simulate complex flows with one or several convoluted free surfaces. This type of flows requires distorted meshes with classical Eulerian mesh-based methods or very fine meshes with Volume of Fluid method. Few 3-D SPH simulations have been carried out to our knowlegde so far, mainly due to prohibitive computational investment since the number of particles required in 3-D is usually too large to be handled by a single processor. In this paper, a parallel 3-D SPH code is presented. Parallelisation validation is discussed… More >