V. Mallardo¹, M.H. Aliabadi²

CMES-Computer Modeling in Engineering & Sciences, Vol.87, No.2, pp. 77-96, 2012, DOI:10.3970/cmes.2012.087.077

Abstract The present paper intends to couple the Fast Multipole Method (FMM) with the Boundary Element Method (BEM) in the 2D scalar wave propagation. The procedure is aimed at speeding the computation of the integrals involved in the governing Boundary Integral Equations (BIEs) on the basis of the distance between source point and integration element. There are three main contributions. First, the approach is of adaptive type in order to reduce the number of floating-point operations. Second, most integrals are evaluated analytically: the diagonal and off-diagonal terms of the H and G matrices by consolidated techniques, More >

Chein-Shan Liu¹

CMES-Computer Modeling in Engineering & Sciences, Vol.86, No.3, pp. 171-198, 2012, DOI:10.3970/cmes.2012.086.171

Abstract In the optimal control theory, the Hamiltonian formalism is a famous one to find an optimal solution. However, when the performance index is complicated or for a degenerate case with a non-convexity of the Hamiltonian function with respect to the control force the Hamiltonian method does not work to find the solution. In this paper we will address this important issue via a quite different approach, which uses the optimal control problem of nonlinear Duffing oscillator as a demonstrative example. The optimally controlled vibration problem of nonlinear oscillator is recast into a nonlinear inverse problem… More >

M.G. Armentano¹, C. Padra², R. Rodríguez³, M. Scheble²

CMES-Computer Modeling in Engineering & Sciences, Vol.84, No.4, pp. 359-382, 2012, DOI:10.3970/cmes.2012.084.359

Abstract In this paper we propose an hp finite element method to solve a two-dimensional fluid-structure vibration problem. This problem arises from the computation of the vibration modes of a bundle of parallel tubes immersed in an incompressible fluid. We use a residual-type a posteriori error indicator to guide an hp adaptive algorithm. Since the tubes are allowed to be different, the weak formulation is a non-standard generalized eigenvalue problem. This feature is inherited by the algebraic system obtained by the discretization process. We introduce an algebraic technique to solve this particular spectral problem. We report More >

M.R. Myers¹, A.B. Jorge², D.E. Yuhas³, D.G. Walker¹

CMES-Computer Modeling in Engineering & Sciences, Vol.83, No.3, pp. 221-248, 2012, DOI:10.3970/cmes.2012.083.221

Abstract An adaptive extended Kalman filter is developed and investigated for a transient heat transfer problem in which a high heat flux spot source is applied on one side of a thin plate and ultrasonic pulse time of flight is measured between spatially separated transducers on the opposite side of the plate. The novel approach is based on the uncertainty in the state model covariance and leverages trends in the extended Kalman filter covariance to drive changes to the state model covariance during convergence. This work is an integral part of an effort to develop a… More >

Yan-Jin Zhu, Yinian Zhu, Li Hui, Sridhar Krishnaswamy

The International Conference on Computational & Experimental Engineering and Sciences, Vol.20, No.1, pp. 29-30, 2011, DOI:10.3970/icces.2011.020.029

Abstract Invited Lecture

Prof. Sridhar Krishnaswamy

Northwestern University, USA More >

G. Kosec¹, B. Šarler^1,2

CMC-Computers, Materials & Continua, Vol.26, No.3, pp. 227-254, 2011, DOI:10.3970/cmc.2011.026.227

Abstract This paper introduces an effective H-adaptive upgrade to solution of the transport phenomena by the novel Local Radial Basis Function Collocation Method (LRBFCM). The transport variable is represented on overlapping 5-noded influence-domains through collocation by using multiquadrics Radial Basis Functions (RBF). The involved first and second derivatives of the variable are calculated from the respective derivatives of the RBFs. The transport equation is solved through explicit time stepping. The H-adaptive upgrade includes refinement/derefinement of one to four nodes to/from the vicinity of the reference node. The number of the nodes added or removed depends on… More >

Chein-Shan Liu¹, Chih-Wen Chang²

CMC-Computers, Materials & Continua, Vol.25, No.2, pp. 107-134, 2011, DOI:10.3970/cmc.2011.025.107

Abstract We consider two inverse problems for estimating radiative coefficients α(x) and α(x, y), respectively, in T_t(x, t) = T_xx(x, t)-α(x)T(x, t), and T_t(x, y, t) = T_xx(x, y, t) + T_yy(x, y, t)-α(x, y)T(x, y, t), where a are assumed to be continuous functions of space variables. A Lie-group adaptive method is developed, which can be used to find a at the spatially discretized points, where we only utilize the initial condition and boundary conditions, such as those for a typical direct problem. This point is quite different from other methods, which need the overspecified final time data. Three-fold advantages can be gained More >

S. Gerace¹, K. Erhart¹, E. Divo^1,2, A. Kassab¹

CMES-Computer Modeling in Engineering & Sciences, Vol.81, No.1, pp. 35-68, 2011, DOI:10.3970/cmes.2011.081.035

Abstract The focus of this work is to demonstrate a novel approach to true CFD automation based on an adaptive Cartesian point distribution process coupled with a Meshless flow solution algorithm. As Meshless method solutions require only an underlying nodal distribution, this approach works well even for complex flow geometries with non-aligned domain boundaries. Through the addition of a so-called shadow layer of body-fitted nodes, application of boundary conditions is simplified considerably, eliminating the stair-casing issues of typical Cartesian-based techniques. This paper describes the approach taken to automatically generate the Meshless nodal distribution, along with the More >

Xiao Zhao¹, Haitian Yang^1,2, Qiang Gao¹

CMES-Computer Modeling in Engineering & Sciences, Vol.74, No.2, pp. 139-160, 2011, DOI:10.3970/cmes.2011.074.139

Abstract A piecewised adaptive algorithm in the time domain is presented to solve the transient convection-diffusion heat transfer problem. By expanding all variables at a time interval, an initial and boundary value problem is decoupled into a series of recursive boundary value problems which can be solved by FEM or other well developed numerical schemes to deal with boundary value problems. A steady computing accuracy can be adaptively maintained via the power increase of the expansion, particularly when the step size varies in the whole computing process. Additionally for the nonlinear cases, there is no requirement More >

A. Gakwaya¹, H. Sharifi², M. Guillot¹, M. Souli³, F. Erchiqui⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.73, No.3, pp. 209-266, 2011, DOI:10.3970/cmes.2011.073.209

Abstract A mechanical computer aided design and engineering system can be used to reduce the design-to-manufacture cycle time in metal forming process. Such a system could be built upon a solid modeling geometry engine and an efficient finite element (FE) solver. The maintenance of a high-quality mesh throughout the analysis is an essential feature of an efficient finite element simulation of large strain metal forming problems. In this paper, a mesh adaptation technique employing the Arbitrary Lagrangian-Eulerian formulation (ALE) is applied to some industrial metal forming problems. An ACIS boundary representation of the solid model is… More >