B. Chrasekhar¹, S. M. Rao²

CMES-Computer Modeling in Engineering & Sciences, Vol.8, No.2, pp. 105-118, 2005, DOI:10.3970/cmes.2005.008.105

Abstract In this work, a simple, robust, and an efficient numerical algorithm to calculate the scattered acoustic fields from complex shaped objects such as aircrafts and missiles, subjected to a plane wave incidence is presented. The work is based on the recently proposed method of moments (MoM) and the potential theory, unlike the standard Helmholtz integral equation (HIE) solution method. For the numerical solution, the scattering structure is approximated by planar triangular patches. For the MoM solution of complex bodies involving open/closed/intersecting surfaces, a unified set of basis functions to approximate the source distribution is defined. More >

C. W. Lan¹, B. C. Yeh

FDMP-Fluid Dynamics & Materials Processing, Vol.1, No.1, pp. 33-44, 2005, DOI:10.3970/fdmp.2005.001.033

Abstract The suppression of unstable Marangoni convection in floating-zone crystal growth by magnetic fields has enjoyed over recent years a widespread use as a reliable and useful strategy. A transversal direction of the field is particularly efficient, but asymmetric zone shapes and thus segregation are induced. Counter-rotation of the feed and of the crystal rods is a common way to improve dopant homogeneity. However, its effects under magnetic fields are complex and have not yet been studied in detail. In the present analysis, three-dimensional (3D) simulations based on a finite-volume/multigrid method are used to illustrate the More >

Carlos J. S. Alves, Pedro R. S. Antunes¹

CMC-Computers, Materials & Continua, Vol.2, No.4, pp. 251-266, 2005, DOI:10.3970/cmc.2005.002.251

Abstract In this work we show the application of the Method of Fundamental Solutions(MFS) in the determination of eigenfrequencies and eigenmodes associated to wave scattering problems. This meshless method was already applied to simple geometry domains with Dirichlet boundary conditions (cf. Karageorghis (2001)) and to multiply connected domains (cf. Chen, Chang, Chen, and Chen (2005)). Here we show that a particular choice of point-sourcescan lead to very good results for a fairly general type of domains. Simulations with Neumann boundary conditionare also considered. More >

N. D. Ngo, K. K. Tamma

CMES-Computer Modeling in Engineering & Sciences, Vol.5, No.2, pp. 103-134, 2004, DOI:10.3970/cmes.2004.005.103

Abstract In the process modeling and manufacturing of large geometrically complex structural net-shaped components comprising of fiber-reinforced composite materials by Resin Transfer Molding (RTM), a polymer resin is injected into a mold cavity filled with porous fibrous preforms. The overall success of the manufacturing process depends on the complete impregnation of the fiber preform by the polymer resin, prevention of polymer gelation during filling, and subsequent avoidance of dry spots. Since the RTM process involves the injection of a cold resin into a heated mold, the associated physics encompasses a moving boundary value problem in conjunction More >

E. Pan¹, X. Jiang¹

CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.1, pp. 77-90, 2004, DOI:10.3970/cmes.2004.006.077

Abstract It is of great importance to understand the factors that contribute to the strain and electrical distributions, which are induced by the misfit strain between a buried quantum wire (QWR) and its surrounding matrix. One of the important factors is the shape or geometry of cross section of the QWR. Utilizing a recent exact closed-form solution [Pan (2004)], we study the model system of QWRs with different shapes and calculate both the surface and internal elastic and piezoelectric fields induced by QWRs embedded in semiconductor GaAs substrates by properly setting the size and location of More >

Kunigal Shivakumar¹, Anil Bhargava²

CMC-Computers, Materials & Continua, Vol.1, No.2, pp. 173-190, 2004, DOI:10.3970/cmc.2004.001.173

Abstract The fiber optic sensor (FOS) embedded perpendicular to reinforcing fibers causes an `Eye' shaped defect. The length is about 16 times fiber optic radius (R_Fos) and height is about 2R_Fos. The eye contains fiber optics in the center surrounded by an elongated resin pocket. Embedding FOS causes geometric distortion of the reinforcing fiber over a height equal to 6 to 8 R_Fos. This defect causes severe stress concentration at the root of the resin pocket, the interface (in the composite) between the optical fiber and the composite, and at 90° to load direction in the composite. The… More >

Michael Yu Wang¹, Xiaoming Wang²

CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.4, pp. 373-396, 2004, DOI:10.3970/cmes.2004.006.373

Abstract This paper addresses the problem of structural shape and topology optimization. A level set method is adopted as an alternative approach to the popular homogenization based methods. The paper focuses on four areas of discussion: (1) The level-set model of the structure’s shape is characterized as a region and global representation; the shape boundary is embedded in a higher-dimensional scalar function as its “iso-surface.” Changes of the shape and topology are governed by a partial differential equation (PDE). (2) The velocity vector of the Hamilton-Jacobi PDE is shown to be naturally related to the shape… More >

F. Auricchio¹, L. Petrini², R. Pietrabissa³, E. Sacco⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.4, No.3&4, pp. 365-380, 2003, DOI:10.3970/cmes.2003.004.365

Abstract Since 80’s many devices were developed to exploit the unique blend of mechanical and biocompatibility properties of shape memory alloys in orthodontic applications. It results in a high clinical effectiveness, but also in a spreading of technical knowledge on the properties of the single appliances. The goal of the present contribution is to contrast this sense of bewilderness and to prepare the basis for a simulationtool able to support the orthodontist choice. In particular a finite-element beam with a one-dimensional constitutive law, able to describe the SMA super elasticity and shape memory effect, is presented: More >

Adnan Ibrahimbegovic¹, Catherine Knopf-Lenoir²

CMES-Computer Modeling in Engineering & Sciences, Vol.4, No.2, pp. 337-344, 2003, DOI:10.3970/cmes.2003.004.337

Abstract In this work we present an unconventional procedure for combining the optimal shape design and nonlinear analysis in mechanics. The main goal of the presented procedure is to enhance computational efficiency for nonlinear problems with respect to the conventional, sequential approach by solving the analysis and design phases simultaneously. A detailed development is presented for the chosen model problem, the 3d rod undergoing large rotations. More >

H. Okumura¹, M. Kawahara¹

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.2, pp. 71-78, 2000, DOI:10.3970/cmes.2000.001.231

Abstract This paper presents a new approach to a shape optimization problem of a body located in the unsteady incompressible viscous flow field based on an optimal control theory. The optimal state is defined by the reduction of drag and lift forces subjected to the body. The state equation used is the transient incompressible Navier--Stokes equations. The shape optimization problem can be formulated to find out geometrical coordinates of the body to minimize the performance function that is defined to evaluate forces subjected to the body. The fractional step method with the implicit temporal integration and More >