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Article
Publication date: 31 July 2019

Dandan Qiu, Lei Luo, Songtao Wang, Bengt Ake Sunden and Xinhong Zhang

This study aims to focus on the surface curvature, jet to target spacing and jet Reynolds number effects on the heat transfer and fluid flow characteristics of a slot jet…

Abstract

Purpose

This study aims to focus on the surface curvature, jet to target spacing and jet Reynolds number effects on the heat transfer and fluid flow characteristics of a slot jet impinging on a confined concave target surface at constant jet to target spacing.

Design/methodology/approach

Numerical simulations are used in this research. Jet to target spacing, H/B is varying from 1.0 to 2.2, B is the slot width. The jet Reynolds number, Rej, varies from 8,000 to 40,000, and the surface curvature, R2/B, varies from 4 to 20. Results of the target surface heat transfer, flow parameters and fluid flow in the concave channel are performed.

Findings

It is found that an obvious backflow occurs near the upper wall. Both the local and averaged Nusselt numbers considered in the defined region respond positively to the Rej. The surface curvature plays a positive role in increasing the averaged Nusselt number for smaller surface curvature (4-15) but affects little as the surface curvature is large enough (> 15). The thermal performance is larger for smaller surface curvature and changes little as the surface curvature is larger than 15. The jet to target spacing shows a negative effect in heat transfer enhancement and thermal performance.

Originality/value

The surface curvature effects are conducted by verifying the concave surface with constant jet size. The flow characteristics are first obtained for the confined impingement cases. Then confined and unconfined slot jet impingements are compared. An ineffective point for surface curvature effects on heat transfer and thermal performance is obtained.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 8
Type: Research Article
ISSN: 0961-5539

Keywords

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Book part
Publication date: 20 January 2005

Leo Egghe

Abstract

Details

Power Laws in the Information Production Process: Lotkaian Informetrics
Type: Book
ISBN: 978-0-12088-753-8

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Article
Publication date: 1 March 1937

J.H. Crowe

THE basic theory of stability has undergone no important modification since the publication of Professor G. H. Bryan's book on Stability in Aviation in 1911. The stability…

Abstract

THE basic theory of stability has undergone no important modification since the publication of Professor G. H. Bryan's book on Stability in Aviation in 1911. The stability equations derived therein serve to‐day with the difference that axes and symbols have now been standardised and with the additional refinement of a non‐dimensional form of the stability equation introduced by H. Glauert. Due to the vastly increased knowledge of aerodrynamic characteristics, however, the stability derivatives are more readily assessable in any particular design case. This applies more particularly to longitudinal stability calculations which may, and indeed often arc, carried through with no wind tunnel tests available apart from a lift and drag curve for the aerofoil section used. There has also been some extension of the use of stability charts for deriving an approximate knowledge of the behaviour of the aeroplane when it receives a disturbance. These charts are exceedingly useful for obtaining periodic time and damping factor, but the assumptions on which they are based should be clearly realized.

Details

Aircraft Engineering and Aerospace Technology, vol. 9 no. 3
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 May 1936

W.H. Sayers

IN all cases, the estimation of airscrew‐engine performance must start with a clear specification of the primary condition for which the airscrew is to be designed. In the…

Abstract

IN all cases, the estimation of airscrew‐engine performance must start with a clear specification of the primary condition for which the airscrew is to be designed. In the majority of cases up to date this primary design condition has been that the airscrew is to absorb the maximum b.h.p. of the engine at maximum permissible r.p.m. at maximum boost height and maximum aircraft speed. (The aircraft speed is obviously an estimate only, but we may assume for the time being that it is reliable.) Under these conditions the airscrew efficiency is required to be the maximum possible.

Details

Aircraft Engineering and Aerospace Technology, vol. 8 no. 5
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 December 1950

J. Kestin

IN the preliminary calculation for the design of a gas turbine or turbocompressor it is necessary to assume a value of the reheat factor R. The contemporary development of…

Abstract

IN the preliminary calculation for the design of a gas turbine or turbocompressor it is necessary to assume a value of the reheat factor R. The contemporary development of gas turbines and rotary compressors has aroused renewed interest in this quantity, which was studied earlier in connexion with steam turbines (refs. 1, 2, 7, 8 and 9). The paper contains an analysis of this value for a gaseous working fluid under appropriate assumptions; it is first calculated for an infinite number of stages with constant and variable specific heats; secondly, exact and approximate formulae are derived for finite numbers of stages of expansion and compression respectively and a method of estimating the heat recovery in turbines for working fluids with variable specific heats is indicated. Similar problems were considered in ref. 10 and the subject matter of Part III was presented to the Aeronautical Research Council (ref. 6).

Details

Aircraft Engineering and Aerospace Technology, vol. 22 no. 12
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 19 May 2020

Encarnación Martínez-Moreno, Gonzalo Garcia-Ros and Ivan Alhama

This study aims to present a new numerical model for the simulation of water flow through porous media of anisotropic character, based on the network simulation method and…

Abstract

Purpose

This study aims to present a new numerical model for the simulation of water flow through porous media of anisotropic character, based on the network simulation method and with the use of the free code Ngspice.

Design/methodology/approach

For its design, it starts directly from the flow conservation equation, which presents several advantages in relation to the numerical simulation of the governing equation in terms of the potential head. The model provides very precise solutions of streamlines and potential patterns in all cases, with relatively small meshes and acceptable calculation times, both essential characteristics when developing a computational tool for engineering purposes. The model has been successfully verified with analytical results for non-penetrating dams in isotropic media.

Findings

Applications of the model are presented for the construction of the flow nets, calculation of uplift pressures, infiltrated flow and average exit gradient in anisotropic scenarios with penetrating dams with and without sheet piles, being all this output information part of the decision process in ground engineering problems involving these retaining structures.

Originality/value

This study presents, for the first time, a numerical network model for seepage problems that is not obtained from the Laplace's governing equation, but from the water flow conservation continuity equation.

Details

Engineering Computations, vol. 37 no. 9
Type: Research Article
ISSN: 0264-4401

Keywords

Content available
Article
Publication date: 8 August 2019

Johann Wilhelm and Werner Renhart

The purpose of this paper is to investigate an alternative to established hysteresis models.

Abstract

Purpose

The purpose of this paper is to investigate an alternative to established hysteresis models.

Design/methodology/approach

Different mathematical representations of the magnetic hysteresis are compared and some differences are briefly discussed. After this, the application of the T(x) function is presented and an inductor model is developed. Implementation details of the used transient circuit simulator code are further discussed. From real measurement results, parameters for the model are extracted. The results of the final simulation are finally discussed and compared to measurements.

Findings

The T(x) function possesses a fast mathematical formulation with very good accuracy. It is shown that this formulation is very well suited for an implementation in transient circuit simulator codes. Simulation results using the developed model are in very good agreement with measurements.

Research limitations/implications

For the purpose of this paper, only soft magnetic materials were considered. However, literature suggests, that the T(x) function can be extended to hard magnetic materials. Investigations on this topic are considered as future work.

Originality/value

While the mathematical background of the T(x) function is very well presented in the referenced papers, the application in a model of a real device is not very well discussed yet. The presented paper is directly applicable to typical problems in the field of power electronics.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 38 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

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Article
Publication date: 19 June 2007

Dwijesh K. Dutta Majumder and Swapan K. Dutta

To develop a mathematical and algorithmic approach of avoiding the limitations of deterministically computing the values of energy, time, position and momentum imposed by…

Abstract

Purpose

To develop a mathematical and algorithmic approach of avoiding the limitations of deterministically computing the values of energy, time, position and momentum imposed by Heisenberg's uncertainity principle (HUP) which is of profound significance from the point of view of some emerging science and technology like quantum computing, nano scale technology and chaotic dynamical systems.

Design/methodology/approach

A parametric method of establishing deterministic solutions for energy and momentum on the basis of quantized energy limits (instead of HUP) if developed in the non‐infinite non‐zero quantized energy limits where hidden deterministic solutions can be obtained for micro/nano structures.

Findings

The philosophical foundations of quantum mechanics as developed by Max Planck, Neils Bohrz, Werner Heisenburg, Dirac and Edwein Schrodinger is based on a duality concept of complimentarity notions. In most general logical sense for any physical reality qualitative dualism have to have a quantitative dualism may be hidden or virtual. The upper and lower limits of the dynamical quantum mechanical observables are determined based on the dimensional considerations for the physical constants H, C, G and H0. The conceptual basis and mathematical framework of the paper in based Norbert Wiener's work on theory of cybernetics and D. Dutta Majumdars' unified cybernetic and general dynamical systems theory.

Research limitations/implications

The testability of the theory needs to be established.

Originality/value

Without challenging HUP this is a contribution of tremendous practical implications.

Details

Kybernetes, vol. 36 no. 5/6
Type: Research Article
ISSN: 0368-492X

Keywords

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Article
Publication date: 1 June 1994

P.R. Masani

Presents the scientific methodology from the enlarged cybernetical perspective that recognizes the anisotropy of time, the probabilistic character of natural laws, and the…

Abstract

Presents the scientific methodology from the enlarged cybernetical perspective that recognizes the anisotropy of time, the probabilistic character of natural laws, and the entry that the incomplete determinism in Nature opens to the occurrence of innovation, growth, organization, teleology communication, control, contest and freedom. The new tier to the methodological edifice that cybernetics provides stands on the earlier tiers, which go back to the Ionians (c. 500 BC). However, the new insights reveal flaws in the earlier tiers, and their removal strengthens the entire edifice. The new concepts of teleological activity and contest allow the clear demarcation of the military sciences as those whose subject matter is teleological activity involving contest. The paramount question “what ought to be done”, outside the empirical realm, is embraced by the scientific methodology. It also embraces the cognitive sciences that ask how the human mind is able to discover, and how the sequence of discoveries might converge to a true description of reality.

Details

Kybernetes, vol. 23 no. 4
Type: Research Article
ISSN: 0368-492X

Keywords

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Article
Publication date: 9 November 2012

Valdemar Melicher and Peter Sergeant

This paper aims to derive a simple and effective but still a reasonably accurate model for electromagnetic problems with hysteretic magnetic properties and/or induced…

Abstract

Purpose

This paper aims to derive a simple and effective but still a reasonably accurate model for electromagnetic problems with hysteretic magnetic properties and/or induced currents in heterogeneous regions in 2D, meant particularly for non‐destructive testing (NDT) of steel cables by eddy‐currents.

Design/methodology/approach

It is assumed that the diffusion of electromagnetic fields in a heterogeneous cable, which consists of many strands, can be described by the Maxwell equations with periodically oscillating coefficients. A computationally efficient model can then be derived. The idea behind this is to replace the heterogeneous material in the cross‐section by a fictitious homogeneous one, whose behaviour at the macroscopic level is a good approximation of the one of the composite material. Such a homogenized model is obtained by employing the two‐scale convergence.

Findings

The model is validated based on experimental electromagnetic data from a steel cable (measured magnetic hysteresis loops) to show that the model is applicable for NDT of cables. The model is useful for studying NDT of cables, both for excitation at low frequency (where changes in magnetic properties are investigated) and at higher frequency (eddy current testing). It is valid for a wide range of amplitudes and frequencies.

Originality/value

From the mathematical point of view the model incorporated a non‐local boundary condition that has to be included in the analysis. From the engineering point of view, by solving an inverse problem based on this model and on measured hysteresis loops at several frequencies, a broader range of defects in the cable can be detected.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 31 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

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