Search results

1 – 10 of over 55000
Article
Publication date: 5 June 2019

Xiang Liu, Fei Guo, Yun Zhang, Junjie Liang, Dequn Li and Huamin Zhou

The purpose of this paper is to develop a coupled approach to solve the pressure–velocity-coupled problem efficiently in the three-dimensional injection molding simulation.

Abstract

Purpose

The purpose of this paper is to develop a coupled approach to solve the pressure–velocity-coupled problem efficiently in the three-dimensional injection molding simulation.

Design/methodology/approach

A fully coupled pressure–velocity algorithm is developed to solve the coupled problem, by treating the pressure gradient term implicitly. And, the Schur complement preconditioned FGMRES is applied to decompose the resulting coupled pressure–velocity equation into pressure and velocity subsystems. Then, BoomerAMG is adopted to solve the pressure subsystem, and block Jacobi preconditioned FGMRES is applied to the velocity subsystem.

Findings

According to the several experiments, the fully coupled pressure–velocity algorithm was demonstrated to have faster convergence than the traditional SIMPLE algorithm, and the calculating time was reduced by up to 70 per cent. And, the Schur complement preconditioned FGMRES worked more efficiently than block Gauss–Seidel preconditioned FGMRES, block-selective AMG and AMG with block ILU(0) smoother and could take at least 47.4 per cent less time. The proposed solver had good scalability for different-size problems, including various cases with different numbers of elements. It also kept good speedup and efficiency in parallel performance.

Originality/value

A coupled solver has been proposed to effectively solve the coupled problem in the three-dimensional injection molding simulation, which is more robust and efficient than existing methods.

Article
Publication date: 7 March 2016

Richard Regueiro, Zheng Duan and Beichuan Yan

– The purpose of this paper is to develop a concurrent multiscale computational method for granular materials in the quasi-static loading regime.

Abstract

Purpose

The purpose of this paper is to develop a concurrent multiscale computational method for granular materials in the quasi-static loading regime.

Design/methodology/approach

Overlapped-coupling between a micropolar linear elastic one-dimensional (1D) mixed finite element (FE) model and a 1D chain of Hertzian nonlinear elastic, glued, discrete element (DE) spheres is presented. The 1D micropolar FEs and 1D chain of DEs are coupled using a bridging-scale decomposition for static analysis.

Findings

It was found that an open-window DE domain may be coupled to a micropolar continuum FE domain via an overlapping region within the bridging-scale decomposition formulation for statics. Allowing the micropolar continuum FE energy in the overlapping region to contribute to the DE energy has a smoothing effect on the DE response, especially for the rotational degrees of freedom (dofs).

Research limitations/implications

The paper focusses on 1D examples, with elastic, glued, DE spheres, and a linear elastic micropolar continuum implemented in 1D.

Practical implications

A concurrent computational multiscale method for granular materials with open-window DE resolution of the large shearing region such as at the interface with a penetrometer skin, will allow more efficient computations by reducing the more costly DE domain calculations, but not at the expense of generating artificial boundary effects between the DE and FE domains.

Originality/value

Open-window DE overlapped-coupling to FE continuum domain, accounting for rotational dofs in both DE and FE methods. Contribution of energy from micropolar FE in overlap region to underlying DE particle energy.

Article
Publication date: 1 June 1993

C.P.T. GROTH and J.J. GOTTLIEB

Partially‐decoupled upwind‐based total‐variation‐diminishing (TVD) finite‐difference schemes for the solution of the conservation laws governing two‐dimensional non‐equilibrium…

81

Abstract

Partially‐decoupled upwind‐based total‐variation‐diminishing (TVD) finite‐difference schemes for the solution of the conservation laws governing two‐dimensional non‐equilibrium vibrationally relaxing and chemically reacting flows of thermally‐perfect gaseous mixtures are presented. In these methods, a novel partially‐decoupled flux‐difference splitting approach is adopted. The fluid conservation laws and species concentration and vibrational energy equations are decoupled by means of a frozen flow approximation. The resulting partially‐decoupled gas‐dynamic and thermodynamic subsystems are then solved alternately in a lagged manner within a time marching procedure, thereby providing explicit coupling between the two equation sets. Both time‐split semi‐implicit and factored implicit flux‐limited TVD upwind schemes are described. The semi‐implicit formulation is more appropriate for unsteady applications whereas the factored implicit form is useful for obtaining steady‐state solutions. Extensions of Roe's approximate Riemann solvers, giving the eigenvalues and eigenvectors of the fully coupled systems, are used to evaluate the numerical flux functions. Additional modifications to the Riemann solutions are also described which ensure that the approximate solutions are not aphysical. The proposed partially‐decoupled methods are shown to have several computational advantages over chemistry‐split and fully coupled techniques. Furthermore, numerical results for single, complex, and double Mach reflection flows, as well as corner‐expansion and blunt‐body flows, using a five‐species four‐temperature model for air demonstrate the capabilities of the methods.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 3 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 16 November 2010

Robert Hamilton, Donald MacKenzie and Hongjun Li

The friction stir welding (FSW) process comprises several highly coupled (and non‐linear) physical phenomena: large plastic deformation, material flow transportation, mechanical…

3366

Abstract

Purpose

The friction stir welding (FSW) process comprises several highly coupled (and non‐linear) physical phenomena: large plastic deformation, material flow transportation, mechanical stirring of the tool, tool‐workpiece surface interaction, dynamic structural evolution, heat generation from friction and plastic deformation. This paper aims to present an advanced finite element (FE) model encapsulating this complex behaviour and various aspects associated with the FE model such as contact modelling, material model and meshing techniques are to be discussed in detail.

Design/methodology/approach

The numerical model is continuum solid mechanics‐based, fully thermo‐mechanically coupled and has successfully simulated the FSW process including plunging, dwelling and welding stages.

Findings

The development of several field variables are quantified by the model: temperature, stress, strain. Material movement is visualized by defining tracer particles at the locations of interest. The numerically computed material flow patterns are in very good agreement with the general findings from experiments.

Originality/value

The model is, to the best of the authors' knowledge, the most advanced simulation of FSW published in the literature.

Details

Engineering Computations, vol. 27 no. 8
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 1 November 2002

Bernhard A. Schrefler, Carmelo E. Majorana, Gabriel A. Khoury and Dariusz Gawin

This paper presents the physical, mathematical and numerical models forming the main structure of the numerical analysis of the thermal, hydral and mechanical behaviour of normal…

2501

Abstract

This paper presents the physical, mathematical and numerical models forming the main structure of the numerical analysis of the thermal, hydral and mechanical behaviour of normal, high‐performance concrete (HPC) and ultra‐high performance concrete (UHPC) structures subjected to heating. A fully coupled non‐linear formulation is designed to predict the behaviour, and potential for spalling, of heated concrete structures for fire and nuclear reactor applications. The physical model is described in more detail, with emphasis being placed upon the real processes occurring in concrete during heating based on tests carried out in several major laboratories around Europe as part of the wider high temperature concrete (HITECO) research programme. A number of experimental and modelling advances are presented in this paper. The stress‐strain behaviour of concrete in direct tension, determined experimentally, is input into the model. The hitherto unknown micro‐structural, hydral and mechanical behaviour of HPC/UHPC were determined experimentally and the information is also built into the model. Two examples of computer simulations concerning experimental validation of the model, i.e. temperature and gas pressure development in a radiatively heated HPC wall and hydro‐thermal and mechanical (damage) performance of a square HPC column during fire, are presented and discussed in the context of full scale fire tests done within the HITECO research programme.

Details

Engineering Computations, vol. 19 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

Book part
Publication date: 26 October 2012

William Ocasio

This chapter first examines the role of attention in the garbage can model of decision making and compares it both to prior approaches in the Carnegie School tradition and the…

Abstract

This chapter first examines the role of attention in the garbage can model of decision making and compares it both to prior approaches in the Carnegie School tradition and the attention-based view of the firm. Both the garbage can model and the attention-based view rely on the same assumption, one that is rarely recognized nor understood – that organizational decision making is characterized by situated attention, where organizational participants vary across time and place in what they attend to. In the garbage can model, decision opportunities are the temporal contexts for situated attention; in the attention-based view, attention is situated in both time and place within the organization's communication channels. In the garbage can, situated attention is also shaped by the ecology of problems and opportunities competing for attention. The final part examines the determinants and consequences of tight versus loose coupling of channels in organizations and its effects on participants’ situated attention. Attention structures external to channels and the architecture of channel structures shape the degree of coupling found in organizations. In viewing coupling as a variable, the chapter suggests that a modified garbage can model, combined with an increased focus on situated attention, provides the foundations for a more general theory of nonroutine decision making.

Details

The Garbage Can Model of Organizational Choice: Looking Forward at Forty
Type: Book
ISBN: 978-1-78052-713-0

Article
Publication date: 3 October 2016

Riccardo Amirante and Paolo Tamburrano

The purpose of this paper is to propose an effective methodology for the industrial design of tangential inlet cyclone separators that is based on the fully three-dimensional (3D…

Abstract

Purpose

The purpose of this paper is to propose an effective methodology for the industrial design of tangential inlet cyclone separators that is based on the fully three-dimensional (3D) simulation of the flow field within the cyclone coupled with an effective genetic algorithm.

Design/methodology/approach

The proposed fully 3D computational fluid dynamics (CFD) model makes use of the Reynold stress model for the accurate prediction of turbulence, while the particle trajectories are simulated using the one-way coupling discrete phase, which is a model particularly effective in case of low concentration of dust. To validate the CFD model, the numerical predictions are compared with experimental data available in the scientific literature. Eight design parameters were chosen, with the two objectives being the minimization of the pressure drop and the maximization of the collection efficiency.

Findings

The optimization procedure allows the determination of the Pareto Front, which represents the set of the best geometries and can be instrumental in taking an optimal decision in the presence of such a trade-off between the two conflicting objectives. The comparison among the individuals belonging to the Pareto Front with a more standard cyclone geometry shows that such a CFD global search is very effective.

Practical implications

The proposed procedure is tested for specific values of the operating conditions; however, it has general validity and can be used in place of typical procedures based on empirical models or engineers’ experience for the industrial design of tangential inlet cyclone separators with low solid loading.

Originality/value

Such an optimization process has never been proposed before for the design of cyclone separators; it has been developed with the aim of being both highly accurate and compatible with the industrial design time.

Details

Engineering Computations, vol. 33 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 1 February 2009

M. Di Gifico, P. Nali and S. Brischetto

Finite elements for the analysis of multilayered plates subjected to magneto‐electro‐elastic fields are developed in this work. An accurate description of the various field…

Abstract

Finite elements for the analysis of multilayered plates subjected to magneto‐electro‐elastic fields are developed in this work. An accurate description of the various field variables has been provided by employing a variable kinematic model which is based on the Unified Formulation, UF. Displacements, magnetic and electric potential have been chosen as independent unknowns. Equivalent single layer and layer‐wise descriptions have been accounted for. Plate models with linear up to fourth‐order distribution in the thickness direction have been compared. The extension of the principle of virtual displacements to magneto‐electro‐elastic continua has been employed to derive finite elements governing equations. According to UF these equations are presented in terms of fundamental nuclei whose form is not affected by kinematic assumptions. Results show the effectiveness of the proposed elements as well as their capability, by choosing appropriate kinematics, to accurately trace the static response of laminated plates subject to magneto‐electro‐elastic fields.

Details

Multidiscipline Modeling in Materials and Structures, vol. 5 no. 2
Type: Research Article
ISSN: 1573-6105

Keywords

Article
Publication date: 2 January 2009

Damijan Markovic, Adnan Ibrahimbegovic and K.C. Park

The purpose of this paper is to describe reduced order modelling based on dynamic flexibility approximation and applied to transient analyses.

Abstract

Purpose

The purpose of this paper is to describe reduced order modelling based on dynamic flexibility approximation and applied to transient analyses.

Design/methodology/approach

This work is based on a recently proposed flexibility‐based component modes synthesis (CMS) approach which was shown to be very efficient for solving large eigenvalue problems. The model reduction approach is based on partionning via the localized Lagrange multipliers method, which makes it very appropriate to handle coupled problems.

Findings

In particular, it is demonstrated in this paper how the utilised model reduction method can be applied only to one part of the structure and efficiently coupled to a full finite element model. The performance of the method is investigated on numerical examples of plate and 3D problems.

Originality/value

The proposed flexibility‐based CMS approach can be used as a very efficient tool for complex engineering structures under dynamic load where the mode superposition method applies. The efficiency of the computations is brought about by the model reduction.

Details

Engineering Computations, vol. 26 no. 1/2
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 1 June 2004

Gérard Degrez, David Vanden Abeele, Paolo Barbante and Benot Bottin

This paper presents a detailed review of the numerical modeling of inductively coupled air plasmas under local thermodynamic equilibrium and under chemical non‐equilibrium. First…

1108

Abstract

This paper presents a detailed review of the numerical modeling of inductively coupled air plasmas under local thermodynamic equilibrium and under chemical non‐equilibrium. First, the physico‐chemical models are described, i.e. the thermodynamics, transport phenomena and chemical kinetics models. Particular attention is given to the correct modelling of ambipolar diffusion in multi‐component chemical non‐equilibrium plasmas. Then, the numerical aspects are discussed, i.e. the space discretization and iterative solution strategies. Finally, computed results are presented for the flow, temperature and chemical concentration fields in an air inductively coupled plasma torch. Calculations are performed assuming local thermodynamic equilibrium and under chemical non‐equilibrium, where two different finite‐rate chemistry models are used. Besides important non‐equilibrium effects, we observe significant demixing of oxygen and nitrogen nuclei, which occurs due to diffusion regardless of the degree of non‐equilibrium in the plasma.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 14 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

1 – 10 of over 55000