Sushil Mohan Ratnaker¹, Sanjay Mittal^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.80, No.3&4, pp. 179-200, 2011, DOI:10.3970/cmes.2011.080.179

Abstract Flow past a circular cylinder looses stability at Re ~ 47 via Hopf bifurcation. The eigenmode responsible for the instability leads to the von Kármán vortex shedding. In this work the linear stability of the flow to other modes, near the critical Re, is investigated. In particular, the study explores the possibility of modes other than the Kármán mode having the largest growth rate for Re < Re_cr. To this extent, global linear stability analysis (LSA) of the steady flow past a circular cylinder is carried out for Re = 45 and 48. In addition to the Kármán modes, two… More >

V. Ungvichian¹, P. Kanongchaiyos¹

CMES-Computer Modeling in Engineering & Sciences, Vol.77, No.3&4, pp. 201-220, 2011, DOI:10.3970/cmes.2011.077.201

Abstract This paper describes an enhancement to Garland and Heckbert's mesh simplification method by using the principal curvatures and directions of each vertex. We calculate the values and directions, before using them to determine the absolute normal curvature in the direction of contraction, and multiplying the curvature with the edge length, the maximum absolute cosine of the angles between the edge and the normals of faces adjacent to either endpoint, and the quadric error of the collapse. We also apply penalties based on compactness and angular and dihedral deviations of the resulting faces. We have implemented these improvements and tested our… More >

Mahdi Izadi¹, Mohd Zainal Abidin Ab. Kadir¹

CMES-Computer Modeling in Engineering & Sciences, Vol.67, No.1, pp. 1-12, 2010, DOI:10.3970/cmes.2010.067.001

Abstract Evaluation of electric field due to indirect lightning strike is an interesting subject. Calculation of electric and magnetic fields in time domain with the consideration of ground conductivity effect in the shortest possible time is an important objective. In this paper, using dipole method, Maxwell's equation and Cooray-Rubinstein formula, a new method for calculation of electric field in time domain is proposed. In addition, this proposed algorithm can also be used to evaluate the effect at the far distance cases of observation point from lightning channel. More >

Alex Ferguson¹, Matthew R. Smith², J.-S. Wu³

CMES-Computer Modeling in Engineering & Sciences, Vol.63, No.1, pp. 79-100, 2010, DOI:10.3970/cmes.2010.063.079

Abstract A novel approach for the use of multiple continuous uniform distributions for reconstruction of the Maxwell-Boltzmann equilibrium probability distribution function is used for the solution of one and two dimensional Euler equations. The Uniform distribution Equilibrium Flux Method (UEFM) is a kinetic-theory based flux solver which calculates true directional, volume to volume fluxes based on integration (over velocity space and physical space) of a sum of uniform probability distribution functions working to approximate the equilibrium distribution function. The resulting flux expressions contain only the Heaviside unit step function and do not require the evaluation of the Exponential or Error Functions.… 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 >

Chein-Shan Liu¹

CMES-Computer Modeling in Engineering & Sciences, Vol.30, No.2, pp. 65-76, 2008, DOI:10.3970/cmes.2008.030.065

Abstract Trefftz method (TM) is one of widely used meshless numerical methods in elliptic type boundary value problems, of which the approximate solution is expressed as a linear combination of T-complete bases, and the unknown coefficients are determined from boundary conditions by solving a linear equations system. However, the accuracy of TM is severely limited by its ill-conditioning. This paper is a continuation of the work of Liu (2007a). The collocation TM is modified and applied to the direct and inverse problems of biharmonic equation in a simply connected plane domain. Due to its well-conditioning of the resulting linear equations system,… More >

S.Y. Long^1,2,3, K.Y. Liu^1,2,4, G.Y. Li¹

CMES-Computer Modeling in Engineering & Sciences, Vol.28, No.3, pp. 203-216, 2008, DOI:10.3970/cmes.2008.028.203

Abstract A meshless local Petrov-Galerkin method (MLPG) for the analysis of the elasto-plastic fracture problem is presented in this paper. The meshless method uses the moving least squares (MLS) to approximate the field functions. The shape function has not Kronecker Delta properties for the trial-function interpolation, and a direct interpolation method is adopted to impose essential boundary conditions. The MLPG method does not involve any domain and singular integrals if body force is ignored. It only involves a regular boundary integral. Two numerical examples show that results obtained by the present method have a good agreement with that by FEM software-ANSYS.… More >

D.L. Young¹, K.H. Chen², J.T. Chen³, J.H. Kao⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.19, No.3, pp. 197-222, 2007, DOI:10.3970/cmes.2007.019.197

Abstract A boundary-type method for solving the Laplace problems using the modified method of fundamental solutions (MMFS) is proposed. The present method (MMFS) implements the singular fundamental solutions to evaluate the solutions, and it can locate the source points on the real boundary as contrasted to the conventional MFS, where a fictitious boundary is needed to avoid the singularity of diagonal term of influence matrices. The diagonal term of influence matrices for arbitrary domain can be novelly determined by relating the MFS with the indirect BEM and are also solved for circular domain analytically by using separable kernels and circulants. The… More >

N. Mai-Duy¹, L. Mai-Cao², T. Tran-Cong³

CMES-Computer Modeling in Engineering & Sciences, Vol.18, No.1, pp. 59-78, 2007, DOI:10.3970/cmes.2007.018.059

Abstract In this paper, an indirect/integrated radial-basis-function network (IRBFN) method is further developed to solve transient partial differential equations (PDEs) governing fluid flow problems. Spatial derivatives are discretized using one- and two-dimensional IRBFN interpolation schemes, whereas temporal derivatives are approximated using a method of lines and a finite-difference technique. In the case of moving interface problems, the IRBFN method is combined with the level set method to capture the evolution of the interface. The accuracy of the method is investigated by considering several benchmark test problems, including the classical lid-driven cavity flow. Very accurate results are achieved using relatively low numbers… More >

George F. Carrier¹, Harry Yeh²

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.2, pp. 113-122, 2005, DOI:10.3970/cmes.2005.010.113

Abstract Sea-bottom displacements associated with seismic events are confined largely to strips of large but finite aspect ratio. We analyze waves that are initiated on such a strip and that propagate across a region of finite depth. We invoke the classical shallow-water-wave theory to obtain rather comprehensive descriptions of the non-dispersive aspects of the waves. The directivity of the energy radiation and the domain of pulse persistence are discussed. More >