J. Labaki¹, E. Mesquita², R. K. N. D. Rajapakse³

CMES-Computer Modeling in Engineering & Sciences, Vol.103, No.5, pp. 281-313, 2014, DOI:10.3970/cmes.2014.103.281

Abstract This paper introduces a numerical model to investigate the vibratory response of elastic and rigid circular plates embedded in viscoelastic, transversely isotropic, three-dimensional layered media. In the present numerical scheme, the boundary-value problem corresponding to the case of time-harmonic concentrated and distributed axisymmetric vertical ring loads within a layered half-space is formulated according to an exact stiffness method. Its solution results in the required influence functions for the modeling of the present problem. The case of an embedded flexible plate is formulated in terms of a variational method. The deflection profile of the plate is written in terms of generalized… More >

A. Roychowdhury^1,2, A. Nandy¹, C.S. Jog¹, R. Pratap^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.103, No.2, pp. 91-110, 2014, DOI:10.3970/cmes.2014.103.091

Abstract We present a hybrid finite element based methodology to solve the coupled fluid structure problem of squeeze film effects in vibratory MEMS devices, such as gyroscopes, RF switches, and 2D resonators. The aforementioned devices often have a thin plate like structure vibrating normally to a fixed substrate, and are generally not perfectly vacuum packed. This results in a thin air film being trapped between the vibrating plate and the fixed substrate which behaves like a squeeze film offering both stiffness and damping. For accurate modelling of such devices the squeeze film effects must be incorporated. Extensive literature is available on… More >

D. Ishihara¹, T. Horie¹

CMES-Computer Modeling in Engineering & Sciences, Vol.101, No.6, pp. 421-440, 2014, DOI:10.3970/cmes.2014.101.421

Abstract In this study, a projection method for the monolithic interaction system of an incompressible fluid and a structure using a new algebraic splitting is proposed. The proposed method splits the monolithic equation system into the equilibrium equations and the pressure Poisson equation (PPE) algebraically using the intermediate velocity in the nonlinear iterations. Since the proposed equilibrium equation satisfies the interface condition, the proposed method is strongly coupled. Moreover, the proposed PPE enforces the incompressibility constraint. Different from previous studies, the proposed algebraic splitting never generates any Schur complement. The proposed method is applied to a channel with a flexible flap,… More >

N. Mitsume¹, S. Yoshimura¹, K. Murotani¹, T. Yamada¹

CMES-Computer Modeling in Engineering & Sciences, Vol.101, No.4, pp. 229-247, 2014, DOI:10.3970/cmes.2014.101.229

Abstract The MPS-FE method, which adopts the Finite Element (FE) method for structure computation and the Moving Particle Simulation (MPS) method for fluid computation involving free surfaces, was developed to solve fluid-structure interaction problems with free surfaces. The conventional MPS-FE method, in which MPS wall boundary particles and finite elements are overlapped in order to exchange information at a fluid-structure interface, is not versatile and reduces the advantages of the software modularity. In this study, we developed a nonoverlapping approach in which the interface in the fluid computation corresponds to the interface in the structure computation through an MPS polygon wall… More >

R. Messahel¹, M. Souli¹

CMES-Computer Modeling in Engineering & Sciences, Vol.96, No.6, pp. 435-455, 2013, DOI:10.3970/cmes.2013.096.435

Abstract Simulation of Fluid Structure Interaction FSI, problems becomes more and more the focus of computational engineering, where FEM (Finite element Methods) for structural mechanics and Finite Volume for CFD are dominant. New formulations have been developed for FSI applications using mesh free methods as SPH method, (Smooth Particle Hydrodynamic). Up to these days very little has been done to compare different methods and assess which one would be more suitable. For small deformation, FEM Lagrangian formulation can solve structure interface and material boundary accurately; the main limitation of the formulation is high mesh distortion for large deformation and moving structure.… More >

Mikael A. Langthjem¹, Masami Nakano²

CMES-Computer Modeling in Engineering & Sciences, Vol.96, No.4, pp. 227-241, 2013, DOI:10.3970/cmes.2013.096.227

Abstract This paper is concerned with a mathematical model of a simple axisymmetric silencer-like model, consisting of a hole-tone feedback system equipped with a tailpipe. The unstable shear layer is modeled via a discrete vortex method, based on axisymmetric vortex rings. The aeroacoustic model is based on the Powell- Howe theory of vortex sound. Boundary integrals are discretized via the boundary element method; but the tailpipe is represented by the exact (one-dimensional) solution. It is demonstrated though numerical examples that this numerical model can display lock-in of the self-sustained flow oscillations to the resonant acoustic oscillations. More >

Changqing Miao¹, Yintao Wei², Xiangqiao Yan¹

CMES-Computer Modeling in Engineering & Sciences, Vol.95, No.6, pp. 519-534, 2013, DOI:10.3970/cmes.2013.095.519

Abstract By using a hybrid displacement discontinuity method, the interactions of three parallel square-hole cracks in an infinite plate subjected to internal pressure are investigated in this paper. Numerical examples are included to illustrate that the numerical approach is very simple and effective for calculating the stress intensity factors (SIFs) of complex plane crack problems. Many numerical results of the SIFs are given and discussed. It is found that a square hole has a shielding effect on crack(s) emanating from the hole. The finding perhaps has an important meaning in engineering. More >

R.A. Amaro Junior¹, L.Y. Cheng¹

CMES-Computer Modeling in Engineering & Sciences, Vol.95, No.2, pp. 87-118, 2013, DOI:10.3970/cmes.2013.095.087

Abstract In this paper simulations of brittle fracture and hydroelastic problems are carried out by using a numerical approach based on the Moving Particle Simulation (MPS) method. It is a meshless method used to model both fluid and elastic solid, and all the computational domain is discretized in Lagrangian particles. A higher order accuracy gradient operator is used herein by adopting a correction matrix. Also, in order to correctly simulate the collision of the fragments, a contact detection algorithm that takes into account the presence of the solid surfaces generated by brittle fracture is proposed. In case of fluid-structure interaction, a… More >

L.L. Chen¹, H.B. Chen², C.J. Zheng³

CMES-Computer Modeling in Engineering & Sciences, Vol.94, No.6, pp. 459-483, 2013, DOI:10.3970/cmes.2013.094.459

Abstract A coupling algorithm based on the finite element method and the wideband fast multipole boundary element method (FEM/wideband FMBEM) is proposed for the simulation of fluid-structure interaction and structural-acoustic sensitivity analysis using the direct differentiation method. The wideband fast multipole method (FMM) formed by combining the original FMM and the diagonal form FMM is used to accelerate the matrix-vector products in the boundary element analysis. The iterative solver GMRES is applied to accelerate the solution of the linear system of equations. The FEM/Wideband FMBEM algorithm makes it possible to predict the effects of arbitrarily shaped vibrating structures on the sound… More >

Xiaokui Yue¹, Yong Xu², Jianping Yuan¹

CMES-Computer Modeling in Engineering & Sciences, Vol.93, No.4, pp. 277-291, 2013, DOI:10.3970/cmes.2013.093.277

Abstract In this paper, a stochastic averaging method is derived for a class of non-linear stochastic systems under parametrical Poisson white noise excitation, which may be used to model the beam-beam interaction models in particle accelerators. The averaged Generalized Fokker-Planck equation is derived and the approximate stationary solution of the averaged Generalized Fokker-Planck equation is solved by using perturbation method. The present method applied in this paper can reduce the dimensions of stochastic ODE from 2n to n, which simplify the complex stochastic ODE, and then the analytical stationary solutions can be obtained. An example is employed to demonstrate the procedure… More >