Delfim Soares Jr.¹

CMES-Computer Modeling in Engineering & Sciences, Vol.105, No.5, pp. 341-360, 2015, DOI:10.3970/cmes.2015.105.341

Abstract In this work, a second-order time-marching procedure for dynamics is discussed, in which enhanced accuracy is enabled. The new technique is unconditionally stable (according to its parameter selection), it has no amplitude decay or overshooting, and it provides reduced period elongation errors. The method is based on displacement-velocity relations, requiring no computation of accelerations. It is efficient, simple and very easy to implement. Numerical results are presented along the paper, illustrating the good performance of the proposed technique. As it is described here, the new method has no drawbacks when compared to the Trapezoidal Rule (TR), which is one of… More >

W. A. El-Askary, A. Abdel-Fattah

CMES-Computer Modeling in Engineering & Sciences, Vol.83, No.4, pp. 425-458, 2012, DOI:10.3970/cmes.2012.083.425

Abstract In the present paper, experimental and numerical studies of heat transfer and the frictional head loss of turbulent flow in a duct with a heated upper surface are performed. Four different arrangements are considered (case 1: without baffles, case 2: one perforated baffle on the upper wall and one solid baffle on the lower wall, case 3: one perforated baffle on the upper wall and one perforated baffle on the lower wall and case 4: two perforated baffles on the upper wall). A numerical code developed by the present authors is simultaneously presented including four different turbulence models; namely: the… More >

J. Badur¹, M. Karcz¹, M. Lemanski¹, L. Nastalek¹

CMES-Computer Modeling in Engineering & Sciences, Vol.73, No.3, pp. 299-310, 2011, DOI:10.3970/cmes.2011.073.299

Abstract In the paper we propose to remove the classical Navier slip condition and replace it with new generalized Navier-Stokes slip boundary conditions. These conditions are postulated to be ones following from the mass and momentum balance within a thin, shell-like moving boundary layer. Owing to this, the problem consistency between the internal and external friction in a viscous fluid is solved within the framework of a proper form of the layer balances, and a proper form of constitutive relations for appropriate friction forces. Finally, the common features of the Navier, Stokes, Maxwell and Reynolds concepts of a boundary slip layer… More >

A.N.M. Imroz Choudhury¹, Michael D. Steffen¹, James E. Guilkey², Steven G.Parker³

CMES-Computer Modeling in Engineering & Sciences, Vol.63, No.2, pp. 117-136, 2010, DOI:10.3970/cmes.2010.063.117

Abstract We present a physically based method for visualizing deformation in particle simulations, such as those describing structural mechanics simulations. The method uses the deformation gradient tensor to transform carefully chosen glyphs representing each particle. The visualization approximates how simulated objects responding to applied forces might look in reality, allowing for a better understanding of material deformation, an important indicator of, for example, material failure. It can also help highlight possible errors and numerical deficiencies in the simulation itself, suggesting how simulations might be changed to yield more accurate results. More >

Chein-Shan Liu¹, Weichung Yeih², Satya N. Atluri³

CMES-Computer Modeling in Engineering & Sciences, Vol.59, No.3, pp. 301-324, 2010, DOI:10.3970/cmes.2010.059.301

Abstract When problems in engineering and science are discretized, algebraic equations appear naturally. In a recent paper by Liu and Atluri, non-linear algebraic equations (NAEs) were transformed into a nonlinear system of ODEs, which were then integrated by a method labelled as the Fictitious Time Integration Method (FTIM). In this paper, the FTIM is enhanced, by using the concept of arepellorin the theory ofnonlinear dynamical systems, to situations where multiple-solutions exist. We label this enhanced method as MSFTIM. MSFTIM is applied and illustrated in this paper through solving boundary-layer problems, boundary-value problems, and eigenvalue problems with multiple solutions. More >

T.B Jönsthövel¹, M.B. van Gijzen², C.Vuik², C. Kasbergen¹, A. Scarpas¹

CMES-Computer Modeling in Engineering & Sciences, Vol.47, No.2, pp. 97-118, 2009, DOI:10.3970/cmes.2009.047.097

Abstract The introduction of computed x-ray tomography allows for the construction of high quality, material-per-element based 3D meshes in the field of structural mechanics. The use of these meshes enables a shift from meso to micro scale analysis of composite materials like cement concrete, rocks and asphalt concrete. Unfortunately, because of the extremely long execution time, memory and storage space demands, the majority of commercially available finite element packages are not capable of handling efficiently the most computationally demanding operation of the finite element solution process, that is, the inversion of the structural stiffness matrix. To address this issue, an efficient… More >

Peter Lucas¹, Alexander H. van Zuijlen¹, Hester Bijl¹

CMES-Computer Modeling in Engineering & Sciences, Vol.41, No.2, pp. 147-176, 2009, DOI:10.3970/cmes.2009.041.147

Abstract Mesh adaptation is a fairly established tool to obtain numerically accurate solutions for flow problems. Computational efficiency is, however, not always guaranteed for the adaptation strategies found in literature. Typically excessive mesh growth diminishes the potential efficiency gain. This paper, therefore, extends the strategy proposed by [Aftosmis and Berger (2002)] to compute the refinement threshold. The extended strategy computes the refinement threshold based on a user desired number of grid cells and adaptations, thereby ensuring high computational efficiency. Because our main interest is flow around wind turbines, the adaptation strategy has been optimized for flow around wind turbine airfoils. The… More >

Y. Başar, O. Kintzel¹

CMES-Computer Modeling in Engineering & Sciences, Vol.4, No.2, pp. 217-230, 2003, DOI:10.3970/cmes.2003.004.217

Abstract The objective of this contribution is the development of a finite element model for finite rotation and large strain analysis of thin walled shells involving geometry intersections. The shell configuration is described by a linear polynomial in the thickness coordinate. The director of the shell is multiplicatively decomposed into a stretching parameter and an inextensible unit vector whose rotation is accomplished by an updated-rotation formulation. A rotation vector with three independent components is used throughout the shell which permits advantageously to consider smooth shells and compound shells by a unified procedure. This formulation is introduced into an isoparametric four-node element.… More >

M. Dandani^1,*, V. Lepiller², A. Ghezal³, P. Desevaux⁴

FDMP-Fluid Dynamics & Materials Processing, Vol.14, No.1, pp. 23-37, 2018, DOI:10.3970/fdmp.2018.014.023

Abstract The present study deals with the numerical visualization of the mixing process in a 2D supersonic ejector. The mixing process is visualized using two CFD flow visualization methods. The first method consists in introducing discrete particles in the secondary flow and computing their trajectories. The second method consists in modeling the diffusion of a passive scalar introduced in one of the two flows. The mixing process is investigated in the case of a conventional 2D supersonic ejector and a second case of an ejector equipped with transverse micro jets. Flow visualizations obtained show the existence of a significant mixing enhancement… More >

Fatima-zohra Bensouici^{1, *}, Saadoun Boudebous²

FDMP-Fluid Dynamics & Materials Processing, Vol.13, No.3, pp. 189-212, 2017, DOI:10.3970/fdmp.2017.013.189

Abstract A numerical work has been performed to analyze the laminar mixed convection of nanofluids confined in a lid driven square enclosure with a central square and isotherm heat source. All the walls are cooled at constant temperature, and the top wall slides rightward at constant velocity. The simulations considered four types of nanofluids (Cu, Ag, Al₂O₃ and TiO₂)-Water. The governing equations were solved using finite volume approach by the SIMPLER algorithm. Comparisons with previously published work are performed and found to be in good agreement. The influence of pertinent parameters such as Richardson number, size of the heat source, solid… More >