Open Access
ARTICLE
J.T. Katsikadelis1, M.S. Nerantzaki1
CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.3, pp. 1-9, 2000, DOI:10.3970/cmes.2000.001.303
Abstract A boundary-only method is presented for the solution of the vibration problem of non-homogeneous membranes. Both free and forced vibrations are considered. The presented method is based on the Analog Equation Method (AEM). According to this method the second order partial differential equation with variable coefficients of hyperbolic type, which governs the dynamic response of the membrane, is substituted by a Poisson's equation describing a quasi-static problem for the homogeneous membrane subjected to a fictitious time dependent load. The fictitious load is established using BEM. Several numerical examples are presented which illustrate the efficiency and the accuracy of the method. More >
Open Access
ARTICLE
H.-G. Kim, S. N. Atluri1
CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.3, pp. 11-32, 2000, DOI:10.3970/cmes.2000.001.313
Abstract The truly meshless local Petrov-Galerkin (MLPG) method holds a great promise in solving boundary value problems, using a local symmetric weak form as a natural approach. In the present paper, in the context of MLPG and the meshless interpolation of a moving least squares (MLS) type, a method which uses primary and secondary nodes in the domain and on the global boundary is introduced, in order to improve the accuracy of solution. The secondary nodes can be placed at any location where one needs to obtain a better resolution. The sub-domains for the shape functions in the MLS approximation are… More >
Open Access
ARTICLE
F. M. A. El-Saeidy1
CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.3, pp. 33-42, 2000, DOI:10.3970/cmes.2000.001.335
Abstract In rotating radial ball bearings supported on elastic casings with the bearing outer ring lightly fitted into the housing, the force due to the ball elastic contact is indeed a rotating load rolling over the housing. For accurate estimation of the dynamic deformations of the casing annulus (hole), which in turn affect the bearing tolerances and hence the magnitudes of the generated forces, effect of the load rotation (motion) should be considered. Considering the integral casing and the outer ring to be a plate, an isoparametric plane stress finite-element (FE) based analytical procedure is presented for the dynamic analysis of… More >
Open Access
ARTICLE
B. Pichler1, H.A. Mang1
CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.3, pp. 43-55, 2000, DOI:10.3970/cmes.2000.001.345
Abstract In order to avoid a fully nonlinear analysis to obtain stability limits on nonlinear load-displacement paths, linear eigenvalue problems may be used to compute estimates of such limits. In this paper an asymptotic approach for assessment of the errors resulting from such estimates is presented. Based on the consistent linearization of the geometrically nonlinear static stability criterion – the so-called consistently linearized eigenvalue problem – higher-order estimation functions can be calculated. They are obtained from a scalar post-calculation performed after the solution of the eigenproblem. Different extensions of these higher-order estimation functions are presented. An ab initio criterion for the… More >
Open Access
ARTICLE
N. D. Ngo, K. K. Tamma1
CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.3, pp. 57-72, 2000, DOI:10.3970/cmes.2000.001.359
Abstract In the process modeling via Resin Transfer Molding (RTM) for thick composite sections, multi-layer preforms with varying thermophysical characteristics across the different layers, or for geometrically complex mold geometries with varying thicknesses, the assumption of a thin shell-like geometry is no longer valid. The flow in the through thickness direction is no longer negligible and current practices of treating the continuously moving flow front as two-dimensional and the temperature and cure as three-dimensional are not representative of the underlying physics. In view of these considerations, in the present study, the focus is on the non-isothermal process modeling of composites employing… More >
Open Access
ARTICLE
J.A.F. Santiago1, L.C. Wrobel2
CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.3, pp. 73-80, 2000, DOI:10.3970/cmes.2000.001.375
Abstract This work presents a boundary element formulation for two-dimensional acoustic wave propagation in shallow water. It is assumed that the velocity of sound in water is constant, the free surface is horizontal, and the seabed is irregular. The boundary conditions of the problem are that the sea bottom is rigid and the free surface pressure is atmospheric.
For regions of constant depth, fundamental solutions in the form of infinite series can be employed in order to avoid the discretisation of both the free surface and bottom boundaries. When the seabed topography is irregular, it is necessary to divide the… More >
Open Access
ARTICLE
F. Simonetti1, R. M. Ardito Marretta2
CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.3, pp. 81-90, 2000, DOI:10.3970/cmes.2000.001.383
Abstract Advanced propellers are being developed to improve the performance and fuel economy of future transport aircraft. To study them, various aerodynamic prediction models and systems (from theory to experiment) have been developed via several approaches (Free Wake Analysis, helicoidal source methods, scale model tests). This study focuses on the development of an efficient numerical method to predict the behaviour of rotor or propeller in forward flight. Based on a variational approach, the present numerical technique allows a significant reduction of computer resources used in the calculation of instantaneous velocities to determine the wake geometry and the three-dimensional vortex flow streaming… More >
Open Access
ARTICLE
Y.C. Shiah1, C.L. Tan1
CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.3, pp. 91-99, 2000, DOI:10.3970/cmes.2000.001.393
Abstract In the direct formulation of the boundary element method (BEM), a volume integral arises in the resulting integral equation if thermal effects are present. The steps to transform this volume integral into boundary ones in an exact analytical manner are reviewed in this paper for two- dimensional anisotropic thermoelasticity. The general applicability of the BEM algorithm for fracture mechanics applications is demonstrated by three crack problems with slanted cracks. The numerical results of the stress intensity factors are presented and compared with those obtained using superposition. More >
Open Access
ARTICLE
N.S. Mera, L. Elliott, D.B. Ingham, D. Lesnic1
CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.3, pp. 101-106, 2000, DOI:10.3970/cmes.2000.001.403
Abstract In this paper the iterative algorithm proposed by [Kozlov and Maz'ya (1990)] for the backward heat conduction problem is extended in order to solve the Cauchy steady state heat conduction problem and the accuracy, convergence and stability of the numerical algorithm are investigated. The numerical results which are obtained confirm that this new iterative BEM procedure is accurate, convergent and stable with respect to increasing the number of boundary elements and decreasing the amount of noise which is added into the input data. More >
Open Access
ARTICLE
R. Mustata1, S. D. Harris2, L. Elliott1, D. Lesnic1, D. B. Ingham1
CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.3, pp. 107-116, 2000, DOI:10.3970/cmes.2000.001.409
Abstract An inverse boundary element method is developed to characterise the components of the hydraulic conductivity tensor K of anisotropic materials. Surface measurements at exposed boundaries serve as additional input to a Genetic Algorithm (GA) using a modified least squares functional that minimises the difference between observed and BEM-predicted boundary pressure and/or hydraulic flux measurements under current hydraulic conductivity tensor component estimates. More >
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