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Article
Publication date: 1 September 1990

Josef Barat

The background and an overall review of the implementation of theRio de Janeiro Rapid Transit System – Metro – with itsimplications in the structure of the transport system within…

Abstract

The background and an overall review of the implementation of the Rio de Janeiro Rapid Transit System – Metro – with its implications in the structure of the transport system within the metropolitan area and in its urban development is provided. Emphasis is given to the social role played by the Metro lines in terms of reducing the travel costs and travelling time of the working population. As such it is also a major political issue which will affect federal and state governments′ priorities and resources allocation.

Details

International Journal of Social Economics, vol. 17 no. 9
Type: Research Article
ISSN: 0306-8293

Keywords

Article
Publication date: 12 August 2022

Isaac Chukwuemezu Okereke, Mohammed S. Ismail, Derek Ingham, Kevin J. Hughes, Lin Ma and Mohamed Pourkashanian

This paper aims to numerically investigate the impact of gas diffusion layer (GDL) anisotropic transport properties on the overall and local performance of polymer electrolyte…

280

Abstract

Purpose

This paper aims to numerically investigate the impact of gas diffusion layer (GDL) anisotropic transport properties on the overall and local performance of polymer electrolyte fuel cells (PEFCs).

Design/methodology/approach

A three-dimensional numerical model of a polymer electrolyte fuel cell with a single straight channel has been developed to investigate the sensitivity of the fuel cell performance to the GDL anisotropic transport properties – gas permeability, diffusivity, thermal conductivity and electrical conductivity. Realistic experimentally estimated GDL transport properties were incorporated into the developed PEFC model, and a parametric study was performed to show the effect of these properties on fuel cell performance and the distribution of the key variables of current density and oxygen concentration within the cathode GDL.

Findings

The results showed that the anisotropy of the GDL must be captured to avoid overestimation/underestimation of the performance of the modelled fuel cell. The results also showed that the fuel cell performance and the distributions of current density and oxygen mass fraction within the cathode GDL are highly sensitive to the through-plane electrical conductivity of the GDL and, to a lesser extent, the through-plane diffusivity, and the thermal conductivity of the GDL. The fuel cell performance is almost insensitive to the gas permeability of the GDL.

Practical implications

This study improves the understanding of the importance of the GDL anisotropy in the modelling of fuel cells and provides useful insights on improving the efficiency of the fuel cells.

Originality/value

Realistic experimentally estimated GDL transport properties have been incorporated into the PEFC model for the first time, allowing for more accurate prediction of the PEFC performance.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 33 no. 2
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 23 July 2021

Nunyi Vachaku Blamah, Hangwelani Magidimisha-Chipungu, Matthew Dayomi and Ayobami Abayomi Popoola

This paper sought to uncover the intrinsic determinants of the choice of transport modes in Nigeria's capital city, Abuja, based on commuters' perceptions on different modes of…

Abstract

Purpose

This paper sought to uncover the intrinsic determinants of the choice of transport modes in Nigeria's capital city, Abuja, based on commuters' perceptions on different modes of transport. The ultimate goal of the study was to come up with suitable multifaceted measures to deter private car usage, while refocusing society's mind-set towards alternative forms of transport, thereby keying into some transport-related sustainable development goals (SDG) goals.

Design/methodology/approach

The study adopted qualitative methods: 320 commuters were surveyed at bus stops and car parks around the city, and respondents were identified using multistage sampling, aided by purposive/convenience sampling, and this number was reached by saturation of themes. Focus group discussions were held with eight screened public officials from relevant (transportation and environment related) agencies/unions in the city. NVivo 10 software was used to thematically analyse the data gathered from a relativist and an interpretive stand point.

Findings

The study found transport mode choice to be intrinsically more motivated by socio-economic forces serving as a basis for other socio-psychological factors. Multifaceted measures, including spatial, socio-economic, environmental and public relation measures, were found suitable to break car-use motives in the study area towards adopting alternative modes of transport, thereby achieving some transport-related SDG targets.

Originality/value

The study was unique as it looked at the intrinsic mode choice determinants from a Sub-Saharan African capital city perspective and provided suitable multifaceted best practiced measures that deemphasised car use while emphasising alternative modes, thereby shifting commuters' mind-set towards environmentally sustainable modes of transport.

Details

Smart and Sustainable Built Environment, vol. 12 no. 1
Type: Research Article
ISSN: 2046-6099

Keywords

Abstract

Details

Public Transport in Developing Countries
Type: Book
ISBN: 978-0-08-045681-2

Article
Publication date: 30 August 2023

P. Sudarsana Reddy and Paluru Sreedevi

Buongiorno’s type nanofluid mass and heat transport appearances inside a cavity filled with gyrotactic microorganisms by captivating thermal radiation is analyzed in the present…

Abstract

Purpose

Buongiorno’s type nanofluid mass and heat transport appearances inside a cavity filled with gyrotactic microorganisms by captivating thermal radiation is analyzed in the present work. Finite element investigation is instigated to examine the converted momentum, temperature, concentration of microorganisms and concentration of nanofluid equations numerically.

Design/methodology/approach

Finite element investigation is instigated to examine the converted momentum, temperature, concentration of microorganisms and concentration of nanofluid equations numerically.

Findings

The sway of these influenced parameters on standard rates of heat transport, nanoparticles Sherwood number and Sherwood number of microorganisms is also illustrated through graphs. It is perceived that the rates of heat transport remarkably intensifies inside the cavity region with amplifying thermophoresis number values.

Originality/value

The research work carried out in this paper is original and no part is copied from others’ work.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 33 no. 12
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 11 October 2018

Salman Arshad, Bo Kong, Alan Kerstein and Michael Oevermann

The purpose of this numerical work is to present and test a new approach for large-scale scalar advection (splicing) in large eddy simulations (LES) that use the linear eddy…

Abstract

Purpose

The purpose of this numerical work is to present and test a new approach for large-scale scalar advection (splicing) in large eddy simulations (LES) that use the linear eddy sub-grid mixing model (LEM) called the LES-LEM.

Design/methodology/approach

The new splicing strategy is based on an ordered flux of spliced LEM segments. The principle is that low-flux segments have less momentum than high-flux segments and, therefore, are displaced less than high-flux segments. This strategy affects the order of both inflowing and outflowing LEM segments of an LES cell. The new splicing approach is implemented in a pressure-based fluid solver and tested by simulation of passive scalar transport in a co-flowing turbulent rectangular jet, instead of combustion simulation, to perform an isolated investigation of splicing. Comparison of the new splicing with a previous splicing approach is also done.

Findings

The simulation results show that the velocity statistics and passive scalar mixing are correctly predicted using the new splicing approach for the LES-LEM. It is argued that modeling of large-scale advection in the LES-LEM via splicing is reasonable, and the new splicing approach potentially captures the physics better than the old approach. The standard LES sub-grid mixing models do not represent turbulent mixing in a proper way because they do not adequately represent molecular diffusion processes and counter gradient effects. Scalar mixing in turbulent flow consists of two different processes, i.e. turbulent mixing that increases the interface between unmixed species and molecular diffusion. It is crucial to model these two processes individually at their respective time scales. The LEM explicitly includes both of these processes and has been used successfully as a sub-grid scalar mixing model (McMurtry et al., 1992; Sone and Menon, 2003). Here, the turbulent mixing capabilities of the LES-LEM with a modified splicing treatment are examined.

Originality/value

The splicing strategy proposed for the LES-LEM is original and has not been investigated before. Also, it is the first LES-LEM implementation using unstructured grids.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 10
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 26 September 2019

Muhammad Sohail, Rahila Naz and Rabeeah Raza

The purpose of this paper is to address the entropy analysis of the 3D flow of Maxwell nanofluid containing gyrotactic microorganism in the presence of homogeneous–heterogeneous…

Abstract

Purpose

The purpose of this paper is to address the entropy analysis of the 3D flow of Maxwell nanofluid containing gyrotactic microorganism in the presence of homogeneous–heterogeneous reactions with improved heat conduction and mass diffusion models over a stretched surface. Improved models are supported out by utilizing Cattaneo–Christov heat flux and generalized Fick’s law, respectively.

Design/methodology/approach

Governing equations which present the given flow phenomenon are modeled in the form of PDEs by applying boundary layer analysis and then suitable makeovers are engaged to transfigure prevailing partial differential equations into a set of ordinary differential equations. Transformed equations are handled via optimal homotopy analysis process in computational tool Mathematica and also a special case of already published work is substantiated and found to be in excellent settlement.

Findings

The bearing of innumerable convoluted physical parameters on velocity, temperature, concentration, reaction rate, the concentration of motile microorganism and entropy generation are presented and deliberated through graphs. Moreover, the convergence of the homotopic solution is presented in tabular form which confirms the reliability of the proposed scheme. It is perceived that mounting values of the magnetic parameter and Brinkman number boosts the irreversibility analysis and Bejan number diminishes for these parameters. Moreover, the growing values of Prandtl and Schmidt numbers reduce the temperature and concentration fields, respectively.

Practical implications

The work contained in this paper has applications in a different industry.

Originality/value

The work contained in this paper is original work and it is good for the researcher in the field of applied mathematics.

Details

Multidiscipline Modeling in Materials and Structures, vol. 16 no. 2
Type: Research Article
ISSN: 1573-6105

Keywords

Article
Publication date: 25 November 2019

Hossein Tamim, Abbas Abbassi and Nasser Fatouraee

The purpose of this paper is to analyze the influence of curvature on the transport of low-density lipoprotein (LDL) through a curved artery and concentration boundary layer…

Abstract

Purpose

The purpose of this paper is to analyze the influence of curvature on the transport of low-density lipoprotein (LDL) through a curved artery and concentration boundary layer characteristics numerically.

Design/methodology/approach

By using a projection method based on the second-order central difference discretization, the authors solve the set of governing equations, which consists of Navier–Stokes, continuity and species transport. The effects of initial straight length, as well as the curvature and wall shear stress (WSS) on LDL transport in a curved artery are established in this paper.

Findings

The obtained numerical results imply that the LDL concentration boundary layer thickness decreases in the outer part of the curved artery and increases in the inner part for both with or without initial straight length. The effect of Reynolds number on the concentration distribution in a curved artery with initial straight length is more pronounced than that on a fully curved artery, although an opposite trend was seen for the curvature ratio. The maximum surface LDL concentration is related to the regions with minimum WSS in the inner part of the curved artery, which has more potential the formation of atherosclerosis.

Originality/value

The authors present a comprehensive concentration distribution of LDL in the concentration boundary layer of the curved artery. The authors also characterize and predict the influence of curvature on the formation and development of atherosclerosis within the arterial wall.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 14 June 2011

Antonin Havelka and Zdeněk Ku˙s

This paper aims to investigate the comfort properties of modern functional clothing, such as moisture and heat transport. Transport properties are evaluated for real barrier…

Abstract

Purpose

This paper aims to investigate the comfort properties of modern functional clothing, such as moisture and heat transport. Transport properties are evaluated for real barrier membrane clothes for sport application, under real weather conditions in Middle Europe.

Design/methodology/approach

The different combination of functional clothing, with barrier membrane, were investigated under different temperatures and relative moistures inside and outside clothing layers. Water vapour permeability was measured under the steady‐state conditions, by sweating guarded‐hotplate test.

Findings

This paper describes the theoretical analysis of moisture transport, and its influence on thermal conductivity; the paper investigates various barrier fabrics for sport apparel, and their ranges of water vapour transport ability under real weather conditions.

Research limitations/implications

All received results are based on the transport of water vapour through a semi‐permeable membrane and are supposed to be conducted mainly within a process of diffusion.

Originality/value

This paper is focused on the theoretical analysis of transport by diffusion of water vapour through porous semi‐permeable barrier textile material, and evaluates the real possibilities for sport applications. The level of transport is limited and mainly depends on the difference of the partial pressures of water vapours outside and inside the porous clothing material.

Details

International Journal of Clothing Science and Technology, vol. 23 no. 2/3
Type: Research Article
ISSN: 0955-6222

Keywords

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