J.A.Ferreira^2,3, P. Oliveira¹, P.M. Silva⁴, A. Carreira^5,3, J.N. Murta⁶

CMES-Computer Modeling in Engineering & Sciences, Vol.60, No.2, pp. 151-180, 2010, DOI:10.3970/cmes.2010.060.151

Abstract This paper focuses on the release of an ophthalmic drug (flurbiprofen) from a loaded copolymer where the drug is simultaneously dispersed in the polymeric matrix and entrapped in particles. The copolymer is based in 2-hydroxyethyl methacrylate co-methacrylic acid and silicone is used to prepare the loaded particles. A mathematical model to simulate the drug release is proposed and a qualitative analysis is performed. In vitro experimental results are compared with simulation results. Contact lens made from the presented copolymer are expected to deliver drug at therapeutical levels for a few days. More >

Ji Joong Moon¹, Seung Jo Kim¹, Minhyung Lee²

CMES-Computer Modeling in Engineering & Sciences, Vol.59, No.3, pp. 275-300, 2010, DOI:10.3970/cmes.2010.059.275

Abstract This paper describes the parallelization of contact/impact simulation for fracture modeling of brittle materials using a node separation scheme (NSS). We successfully demonstrated the fracture modeling of brittle materials using a cohesive fracture model. Since a NSS continuously generates new free surfaces as the computation progresses, the methodology requires increased computational time. To perform a simulation within a reasonable time period, a parallelization study is conducted. Particular methods for effective parallelization, especially for brittle materials, are described in detail. The crucial and most difficult strategy is the management of the data structure and communication needed to handle new contact nodes… More >

F.P. Mariano¹, L.Q. Moreira¹, A. Silveira-Neto¹, C.B. da Silva², J.C.F. Pereira²

CMES-Computer Modeling in Engineering & Sciences, Vol.59, No.2, pp. 181-216, 2010, DOI:10.3970/cmes.2010.059.181

Abstract A new numerical methodology combining Fourier pseudo-spectral and immersed boundary methods - IMERSPEC - is developed for fluid flow problems governed by the incompressible Navier-Stokes equations. The numerical algorithm consists in a classical Fourier pseudo-spectral methodology using the collocation method where wall boundary conditions are modelled by using an immersed boundary method (IBM). The performance of that new methodology is exemplified in two-dimensional numerical simulations of Green-Taylor decaying vortex, lid-driven cavity and flow over a square cylinder. The convergence rate, the accuracy, the influence of the Reynolds number and the external domain size are analyzed. This new method combines some… More >

C. Becker¹, S. Jox², G. Meschke³

CMES-Computer Modeling in Engineering & Sciences, Vol.57, No.3, pp. 245-278, 2010, DOI:10.3970/cmes.2010.057.245

Abstract A three-dimensional numerical model based on the Extended Finite Element Method (X-FEM) is presented for the simulation of cohesive cracks in cementitious materials, such as concrete, in a hygro-mechanical framework. Enhancement functions for the small scale resolution of the displacement jump across cracks in the context of the X-FEM is used in conjunction with a higher order family of hierarchical shape functions for the representation of the large scale displacement field of the investigated structure. Besides the theoretical and computational formulation in a multiphase context, aspects of the implementation, such as integration and crack tracking algorithms, are discussed. Representative numerical… More >

A. Frangi¹, M. Pagani¹, U. Perego¹, R. Borsari²

CMES-Computer Modeling in Engineering & Sciences, Vol.57, No.3, pp. 205-224, 2010, DOI:10.3970/cmes.2010.057.205

Abstract This paper is concerned with the finite element simulation of a thin membrane cutting by a sharp blade. Smeared crack finite element approaches appear to be unsuitable for this purpose, since very small elements would be required to conform to the sharp edge of the cutter. Furthermore, when the membrane material is very ductile, classical interface cohesive elements, where the cohesive forces are transmitted in the direction of the crack opening displacement, cannot correctly reproduce situations where the blade crosses the process zone. A simplified approach, based on the new concept of "directional" cohesive elements, is here proposed for a… More >

Chun Yang^1,2, Dalin Tang^2,3 Satya Atluri⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.57, No.1, pp. 51-76, 2010, DOI:10.3970/cmes.2010.057.051

Abstract Cardiovascular disease (CVD) is becoming the number one cause of death worldwide. Atherosclerotic plaque rupture and progression are closely related to most severe cardiovascular syndromes such as heart attack and stroke. Mechanisms governing plaque rupture and progression are not well understood. A computational procedure based on three-dimensional 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… More >

Y. T. Gu¹, P. Zhuang², F. Liu³

CMES-Computer Modeling in Engineering & Sciences, Vol.56, No.3, pp. 303-334, 2010, DOI:10.3970/cmes.2010.056.303

Abstract Recently, the numerical modelling and simulation for anomalous subdiffusion equation (ASDE), which is a type of fractional partial differential equation(FPDE) and has been found with widely applications in modern engineering and sciences, are attracting more and more attentions. The current dominant numerical method for modelling ASDE is Finite Difference Method (FDM), which is based on a pre-defined grid leading to inherited issues or shortcomings. This paper aims to develop an implicit meshless approach based on the radial basis functions (RBF) for numerical simulation of the non-linear ASDE. The discrete system of equations is obtained by using the meshless shape functions… More >

Ying Liu¹, Yufeng Nie², Weiwei Zhang², Lei Wang²

CMES-Computer Modeling in Engineering & Sciences, Vol.55, No.1, pp. 89-110, 2010, DOI:10.3970/cmes.2010.055.089

Abstract In the light of the ideas and treatment technologies about molecular dynamics simulation and bubble meshing, a new approach of node placement for the meshless method called node placement method by bubble simulation (NPBS method), is proposed. Nodes are seen as the centers of the bubbles which can be moved by their interacting forces. Through dynamic simulation, bubbles are placed into a near-optimal configuration, and the centers of bubbles will form a good-quality node distribution in the domain. This process doesn't need updating the mesh connection constantly, i.e., is totally meshfree. Some example results show that the uniform point sets… More >

Z. T. Ma¹, X. Zhang^1,2, P. Huang¹

CMES-Computer Modeling in Engineering & Sciences, Vol.55, No.1, pp. 61-88, 2010, DOI:10.3970/cmes.2010.055.061

Abstract The Material Point Method (MPM) is more expensive in terms of storage than other methods, as MPM makes use of both mesh and particle data. Therefore, it is critical to develop an efficient MPM framework for engineering applications, such as impact and explosive simulations. This paper presents a new architecture for MPM computer code, developed using object-oriented design, which enables MPM analysis of a mass of grains, large deformation, high strain rates and complex material behavior. It is flexible, extendible, and easily modified for a variety of MPM analysis procedures. An MPM scheme combining contact algorithm with USF, USL and… More >

G.S. Li¹, D. Yao², Y.Z. Wang³, H.Y. Jiang²

CMES-Computer Modeling in Engineering & Sciences, Vol.51, No.1, pp. 53-72, 2009, DOI:10.3970/cmes.2009.051.053

Abstract In this paper, an undisturbed soil-column infiltrating experiment is investigated, and a mathematical model describing multi-components solutes transport behaviors in the column is put forward by combing hydro-chemical analysis with advection dispersion mechanisms, which is a group of advection-dispersion-reaction partial differential equations. Since the model involving six reaction coefficients which can not be obtained directly, an optimal perturbation regularization algorithm of determining these parameters is performed, and numerical simulations under different conditions are carried out. Furthermore, the inversion algorithm is applied to solve the real inverse problem by utilizing the measured breakthrough data. The reconstruction data basically coincide with the… More >