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Article

Haruhiko Kohno

This paper aims to present an improved finite element method used for achieving faster convergence in simulations of incompressible fluid flows. For stable computations of…

Abstract

Purpose

This paper aims to present an improved finite element method used for achieving faster convergence in simulations of incompressible fluid flows. For stable computations of incompressible fluid flows, it is important to ensure that the flow field satisfies the equation of continuity in each element of a generally distorted mesh. The study aims to develop a numerical approach that satisfies this requirement based on the highly simplified marker-and-cell (HSMAC) method and increases computational speed by introducing a new algorithm into the simultaneous relaxation of velocity and pressure.

Design/methodology/approach

First, the paper shows that the classical HSMAC method is equivalent to a Jacobi-type method in terms of the simultaneous relaxation of velocity and pressure. Then, a Gauss–Seidel or successive over-relaxation (SOR)-type method is introduced in the Newton–Raphson iterations to take into account all the derivative terms in the first-order Taylor series expansion of a nodal-averaged error explicitly. Here, the nine-node quadrilateral (Q2–Q1) elements are used.

Findings

The new finite element approach based on the improved HSMAC algorithm is tested on fluid flow problems including the lid-driven square cavity flow and the flow past a circular cylinder. The results show significant improvement of the convergence property with the accuracy of the numerical solutions kept unchanged even on a highly distorted mesh.

Originality/value

To the best of the author’s knowledge, the idea of using the Gauss–Seidel or SOR method in the simultaneous relaxation procedure of the HSMAC method has not been proposed elsewhere.

Details

Engineering Computations, vol. 37 no. 2
Type: Research Article
ISSN: 0264-4401

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Abstract

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Executive Burnout
Type: Book
ISBN: 978-1-78635-285-9

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Article

David Greenaway and Chris Milner

The distinction between nominal and effective tariffs (or protection) is well established in the theoretical literature, albeit in the context of the traditional analysis…

Abstract

The distinction between nominal and effective tariffs (or protection) is well established in the theoretical literature, albeit in the context of the traditional analysis of inter‐industry trade flows. This analysis is based upon assumptions such as product and production homogeneity, non‐increasing returns, armslength trade, and small open economy country conditions. Relaxation of some or all of these assumptions has direct implications for effective protection analysis under any type of trade flows. As is now widely recognised, however, relaxation of these assumptions is also likely to be associated with intra‐industry specialisation and exchange. It is to this wider issue of effective protection analysis in the context of “within‐industry” specialisation (vertical and/or horizontal) and of two‐way trade, that this paper is addressed.

Details

Journal of Economic Studies, vol. 14 no. 5
Type: Research Article
ISSN: 0144-3585

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Article

Czesław Kundera and Jerzy Bochnia

– This paper aims to investigate the suitability of additive manufacturing to produce O-ring seals.

Abstract

Purpose

This paper aims to investigate the suitability of additive manufacturing to produce O-ring seals.

Design/methodology/approach

The O-rings were made by the PolyJet-Matrix technology using four different digital materials and then tested for relaxation properties under static and dynamic (sliding) conditions. The approximation of the relaxation curves involved modelling with a Prony series.

Findings

The PolyJet-Matrix technology offers new opportunities to model elastomeric elements, with examples being the O-rings produced and tested for their relaxation properties. Describing the behaviour of the particular materials fabricated with this technology by using relaxation functions will extend the knowledge base on digital materials.

Research limitations/implications

The four types of photopolymers used in the experiment differed in viscoelastic properties. The analysis of the stress relaxation of the O-ring models was performed at four different step displacements of the loading element.

Practical implications

The test results may be useful for the design of O-ring seals made of new elastomeric materials. The relaxation properties of the O-rings made of such materials can be applied to analyse the dynamics of seals, for instance, face seals.

Originality/value

The originality of the work lies in the use of digital materials to design and produce elastomeric elements with different relaxation properties, which was confirmed by the test results. This paper presents results of a relaxation analysis for a ring model and the material that the ring is made of. It also discusses how 3D printing and digital materials can be applied in practice.

Details

Rapid Prototyping Journal, vol. 20 no. 6
Type: Research Article
ISSN: 1355-2546

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Article

J. AKHTAR and S. AHMAD

The optimisation of grid structure and relaxation parameter is considered in this paper in connection with two‐dimensional finite difference solution of Poisson's equation…

Abstract

The optimisation of grid structure and relaxation parameter is considered in this paper in connection with two‐dimensional finite difference solution of Poisson's equation for determining the field profile in a reverse biased planar type p?n junction. By dividing the planar junction into regions with rectangular and circular symmetry, regional optimisations have been carried out using small area test sites. Having obtained the optimal grid size and relaxation parameter for each region, the complete solution was obtained easily with very fast convergence. The method involved in this kind of regional optimisation is presented in detail with discussions on its comparative usefulness with other known techniques.

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COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 8 no. 4
Type: Research Article
ISSN: 0332-1649

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Article

J. Akhtar

Optimisation of the discretising steps in the space and time domains has been studied for the evaluation of corresponding optimum value of over‐relaxation parameter in the…

Abstract

Optimisation of the discretising steps in the space and time domains has been studied for the evaluation of corresponding optimum value of over‐relaxation parameter in the numerical solution of transient heat flow equation using successive‐over‐relaxation method in the finite difference code. No closed form solutions are available for the optimisation of a complete set of involved parameters in such problems. The present work deals quantitatively with the need for a more generalised closed form relation involving discretising steps in the space and the time domains for an optimal over‐relaxation parameter. The maximum finite difference error and the number of iterations required to achieve a reasonable error tolerance in the functional value are the two criteria used to obtain an optimised set of parameters. The effect of deviation from the optimised values of any of the involved parameters has been shown over a model problem of one‐dimensional diamond‐IIa medium of 100 micrometer length and for a time duration of 1.24 micro‐seconds.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 19 no. 4
Type: Research Article
ISSN: 0332-1649

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Abstract

Details

Executive Burnout
Type: Book
ISBN: 978-1-78635-285-9

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Article

This is a textbook on a subject that has been developed almost entirely within the last decade. It deals with a method of solving problems by successive approximations…

Abstract

This is a textbook on a subject that has been developed almost entirely within the last decade. It deals with a method of solving problems by successive approximations that have wide applications in engineering and physics.

Details

Aircraft Engineering and Aerospace Technology, vol. 13 no. 6
Type: Research Article
ISSN: 0002-2667

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Article

George K. Stylios

Examines the twelfth published year of the ITCRR. Runs the whole gamut of textile innovation, research and testing, some of which investigates hitherto untouched aspects…

Abstract

Examines the twelfth published year of the ITCRR. Runs the whole gamut of textile innovation, research and testing, some of which investigates hitherto untouched aspects. Subjects discussed include cotton fabric processing, asbestos substitutes, textile adjuncts to cardiovascular surgery, wet textile processes, hand evaluation, nanotechnology, thermoplastic composites, robotic ironing, protective clothing (agricultural and industrial), ecological aspects of fibre properties – to name but a few! There would appear to be no limit to the future potential for textile applications.

Details

International Journal of Clothing Science and Technology, vol. 18 no. 6
Type: Research Article
ISSN: 0955-6222

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Article

Lelanie Smith, Oliver Oxtoby, A. Malan and Josua Meyer

– The purpose of this paper is to introduce a unique technique to couple the two-integral boundary layer solutions to a generic inviscid solver in an iterative fashion.

Abstract

Purpose

The purpose of this paper is to introduce a unique technique to couple the two-integral boundary layer solutions to a generic inviscid solver in an iterative fashion.

Design/methodology/approach

The boundary layer solution is obtained using the two-integral method to solve displacement thickness point by point with a local Newton method, at a fraction of the cost of a conventional mesh-based, full viscous solution. The boundary layer solution is coupled with an existing inviscid solver. Coupling occurs by moving the wall to a streamline at the computed boundary layer thickness and treating it as a slip boundary, then solving the flow again and iterating. The Goldstein singularity present when solving boundary layer equations is overcome by solving an auxiliary velocity equation along with the displacement thickness.

Findings

The proposed method obtained favourable results when compared with the analytical solutions for flat and inclined plates. Further, it was applied to modelling the flow around a NACA0012 airfoil and yielded results similar to those of the widely used XFOIL code.

Originality/value

A unique method is proposed for coupling of the boundary layer solution to the inviscid flow. Rather than the traditional transpiration boundary condition, mesh movement is employed to simulate the boundary layer thickness in a more physically meaningful way. Further, a new auxiliary velocity equation is presented to circumvent the Goldstein singularity.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 23 no. 8
Type: Research Article
ISSN: 0961-5539

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