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Article
Publication date: 19 July 2019

Dhanush Vittal Shenoy, Mostafa Safdari Shadloo, Jorge Peixinho and Abdellah Hadjadj

Fluid flows in pipes whose cross-sectional area are increasing in the stream-wise direction are prone to separation of the recirculation region. This paper aims to…

Abstract

Purpose

Fluid flows in pipes whose cross-sectional area are increasing in the stream-wise direction are prone to separation of the recirculation region. This paper aims to investigate such fluid flow in expansion pipe systems using direct numerical simulations. The flow in circular diverging pipes with different diverging half angles, namely, 45, 26, 14, 7.2 and 4.7 degrees, are considered. The flow is fed by a fully developed laminar parabolic velocity profile at its inlet and is connected to a long straight circular pipe at its downstream to characterise recirculation zone and skin friction coefficient in the laminar regime. The flow is considered linearly stable for Reynolds numbers sufficiently below natural transition. A perturbation is added to the inlet fully developed laminar velocity profile to test the flow response to finite amplitude disturbances and to characterise sub-critical transition.

Design/methodology/approach

Direct numerical simulations of the Navier–Stokes equations have been solved using a spectral element method.

Findings

It is found that the onset of disordered motion and the dynamics of the localised turbulence patch are controlled by the Reynolds number, the perturbation amplitude and the half angle of the pipe.

Originality/value

The authors clarify different stages of flow behaviour under the finite amplitude perturbations and shed more light to flow physics such as existence of Kelvin–Helmholtz instabilities as well as mechanism of turbulent puff shedding in diverging pipe flows.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 5 July 2021

Benoit Bourguignon, Harold Boeck and Thomas Brashear Alejandro

Salespeople are at the forefront of the external environment where they act as the first responders to critical events and their resulting business turbulence. How the…

Abstract

Purpose

Salespeople are at the forefront of the external environment where they act as the first responders to critical events and their resulting business turbulence. How the salesforce responds to turbulence is, therefore, of great interest both theoretically and in practice. The paper aims to rekindle interest in agility selling, which is the most adequate behavioral sales model to exploit environmental uncertainty.

Design/methodology/approach

An organizational autoethnography complemented with data from in-depth interviews with key salespeople involved in turbulence resulted in the development of eight case studies.

Findings

Salespeople use agility selling through four possible responsive roles. They amplify, innovate, cooperate or mitigate turbulence to exploit its ensuing opportunity or minimize its negative effect for both the supplier and the customer. The article enhances the agility selling model by putting three core abilities in the forefront: (1) forecasting turbulence from critical events, (2) responding to changes quickly and adequately and (3) exploiting changes as opportunities.

Research limitations/implications

The article argues that critical events are the cause of the turbulence that the salesforce must deal with before it hits the dyad. Agility selling represents an untapped research opportunity in business-to-business sales, and sales management, as well as within the overall agile organization.

Practical implications

Sales organizations would greatly benefit in implementing training of agility selling’s core abilities because responsiveness is a valuable tool for salespeople in times of turbulence.

Originality/value

The study is the first to empirically demonstrate the existence of agility selling.

Details

Journal of Business & Industrial Marketing, vol. 36 no. 8
Type: Research Article
ISSN: 0885-8624

Keywords

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Article
Publication date: 1 June 1969

E. Galletto and R. Gasparini

In thermal and nuclear power plants, numerous corrosion phenomena observed in copper alloy condenser tube nests have been identified by means of metallography. Particular…

Abstract

In thermal and nuclear power plants, numerous corrosion phenomena observed in copper alloy condenser tube nests have been identified by means of metallography. Particular importance has been given in the paper to verification of secondary dezincification, initiated at the boundaries of the α‐grains in copper tubes. Typical phenomena of corrosion under stress and of erosion‐corrosion have been observed in other copper alloy tube nests, with circulation of sea and river water. In some instances a semi‐quantitative check of the phenomenon on the whole tube nest, by means of eddy currents, has been made possible through the simultaneous application of metallographic analysis.

Details

Anti-Corrosion Methods and Materials, vol. 16 no. 6
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 1 May 1976

L. Ferretti, E. Traverso and G. Ventura

Summary The corrosion behaviour of a naval mild steel has been studied in the natural environment in a part of the Port of Genoa, where the water temperature is evelated…

Abstract

Summary The corrosion behaviour of a naval mild steel has been studied in the natural environment in a part of the Port of Genoa, where the water temperature is evelated by a hot effluent from a generating station.

Details

Anti-Corrosion Methods and Materials, vol. 23 no. 5
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 1 August 1962

G. Butler and H.C.K. Ison

In this third and final section the influence of design in relation to corrosion is considered and methods of water treatment and inhibition summarised. The work on…

Abstract

In this third and final section the influence of design in relation to corrosion is considered and methods of water treatment and inhibition summarised. The work on flowing water corrosion at the National Chemical Laboratory, it is hoped, will provide a more sound basis for the prediction of the probable corrosivity of water and for recommendations for corrosion prevention.

Details

Anti-Corrosion Methods and Materials, vol. 9 no. 8
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 3 January 2017

Vinicius Malatesta, Josuel Kruppa Rogenski and Leandro Franco de Souza

The centrifugal instability mechanism of boundary layers over concave surfaces is responsible for the development of quasi-periodic, counter-rotating vortices aligned in a…

Abstract

Purpose

The centrifugal instability mechanism of boundary layers over concave surfaces is responsible for the development of quasi-periodic, counter-rotating vortices aligned in a streamwise direction known as Görtler vortices. By distorting the boundary layer structure in both the spanwise and the wall-normal directions, Görtler vortices may modify heat transfer rates. The purpose of this study is to conduct spatial numerical simulation experiments based on a vorticity–velocity formulation of the incompressible Navier–Stokes system of equations to quantify the role of the transition in the heat transfer process.

Design/methodology/approach

Experiments are conducted using an in-house, parallel, message-passing code. Compact finite difference approximations and a spectral method are used to approximate spatial derivatives. A fourth-order Runge–Kutta method is adopted for time integration. The Poisson equation is solved using a geometric multigrid method.

Findings

Results show that the numerical method can capture the physics of transitional flows over concave geometries. They also show that the heat transfer rates in the late stages of the transition may be greater than those for either laminar or turbulent ones.

Originality/value

The numerical method can be considered as a robust alternative to investigate heat transfer properties in transitional boundary layer flows over concave surfaces.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 27 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 1 April 1989

Peter Wells

Innovative stress wave sensors could find wide application in industry.

Abstract

Innovative stress wave sensors could find wide application in industry.

Details

Sensor Review, vol. 9 no. 4
Type: Research Article
ISSN: 0260-2288

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Article
Publication date: 11 April 2016

Christine Wamsler and Ebba Brink

Cities are both at risk and the cause of risk. The interconnectedness of urban features and systems increases the likelihood of complex disasters and a cascade or “domino”…

Abstract

Purpose

Cities are both at risk and the cause of risk. The interconnectedness of urban features and systems increases the likelihood of complex disasters and a cascade or “domino” effect from related impacts. However, the lack of research means that our knowledge of urban risk is both scarce and fragmented. Against this background, the purpose of this paper is to examine the unique dynamics of risk in urban settings.

Design/methodology/approach

Based on literal reading, grounded theory and systems analysis, this conceptual paper presents a framework for understanding and addressing urban risk. It conceptualizes how interdependent, interconnected risk is shaped by urban characteristics and exemplifies its particularities with data and analysis of specific cases. From this, it identifies improvements both in the content and the indicators of the successor to the Hyogo Framework for Action (HFA2) that will be adopted in 2015.

Findings

While it is common to see disasters as “causes”, and the destruction of the built environment as “effects”, this paper highlights that the intricate links between cities and disasters cannot be described by a unidirectional cause-and-effect relationship. The city–disasters nexus is a bidirectional relationship, which constantly shapes, and is shaped by, other processes (such as climate change).

Practical implications

This paper argues that in-depth knowledge of the links between cities’ characteristic features, related systems and disasters is indispensable for addressing root causes and mainstreaming risk reduction into urban sector work. It enables city authorities and other urban actors to improve and adapt their work without negatively influencing the interconnectedness of urban risk.

Originality/value

This paper presents a framework for understanding and addressing urban risk and further demonstrates how the characteristics of the urban fabric (physical/spatial, environmental, social, economic and political/institutional) and related systems increase risk by: intensifying hazards or creating new ones, exacerbating vulnerabilities and negatively affecting existing response and recovery mechanisms.

Details

International Journal of Disaster Resilience in the Built Environment, vol. 7 no. 2
Type: Research Article
ISSN: 1759-5908

Keywords

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Expert briefing
Publication date: 12 January 2018

Ugandan military engagement in eastern Congo.

Details

DOI: 10.1108/OXAN-DB228030

ISSN: 2633-304X

Keywords

Geographic
Topical
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Article
Publication date: 20 February 2007

Antonios Antoniou, Gioia M. Pescetto and Ibrahim Stevens

The paper seeks to investigate conditional correlations and conditional volatility spillovers across international stock markets and industrial sectors from the…

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Abstract

Purpose

The paper seeks to investigate conditional correlations and conditional volatility spillovers across international stock markets and industrial sectors from the perspective of the UK investor.

Design/methodology/approach

Utilizing the DCC model, the paper extracts the time‐varying conditional correlations between the UK, US and European stock markets and industrial sectors. It also uses the multivariate generalized autoregressive conditional heteroscedasticity (MVGARCH) to assess the transmission of volatility from the US and European stock markets to the UK.

Findings

The findings suggest that the UK equity market is more integrated with Europe, in terms of both aggregate stock markets and sectors. Correlations are higher during bear markets and tend to fall during periods of recovery. The sectoral analysis also provides interesting insights into the dynamics of volatility transmission across sectors.

Research limitations/implications

The results suggest that the search for a better understanding of the dynamics of correlations between markets and sectors must continue.

Practical implications

The investigation raises interesting questions for investors and regulators, as well as theoretical finance. For example, the finding that correlations increase in bear markets suggests that hedging strategies need to be revisited. The existence of sectoral idiosyncratic volatility offers further evidence that arbitrage may at times become more risky and thus limited.

Originality/value

The findings from analysing both market‐wide and sectoral integration raises the overarching question of whether studies of market integration and portfolio diversification, as well as the authorities overseeing financial stability, should be focusing on sectoral rather than market‐wide analysis.

Details

Managerial Finance, vol. 33 no. 3
Type: Research Article
ISSN: 0307-4358

Keywords

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