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Article
Publication date: 7 November 2022

Elena B. Martin, Francisco Sastre, Angel Velazquez and Abderrahmane Baïri

This paper aims to study the influence that the second invariant of the rate-of-strain tensor of a power law polymeric fluid (aqueous solution of hydroxyethyl cellulose [HEC]) has…

91

Abstract

Purpose

This paper aims to study the influence that the second invariant of the rate-of-strain tensor of a power law polymeric fluid (aqueous solution of hydroxyethyl cellulose [HEC]) has on convective mixing performance downstream of a 3D confined oscillating prism. Newtonian and non-Newtonian Reynolds numbers, the mass concentration of HEC and prism oscillation frequency were varied.

Design/methodology/approach

A conceptual problem was designed. Its objective was to analyze the convective mixing of two adjacent flow streams when they pass around a moving confined prism. The rectangular prism had a square section, and its sinusoidal motion was prescribed inside a channel with a square section too. OpenFOAM libraries were used to simulate the flow field. Regarding prism motion, the icoDyMFoam solver was used. The problem was analyzed both at the global level (mixing parameter) and local level (detailed flow topology).

Findings

For constant Reynolds number, increasing mass concentrations of HEC (in the range from 0.2% to 0.5%) led to better mixing parameters. The improvement was linked to the effect that the second invariant of the rate-of-strain tensor had on flow topology. It was found that mixing is maximum when the prism motion and its wake (the frequency of the first instability) are synchronized. In practical terms, this means that the optimum stirring frequency does not need to be very high; it suffices that it ensures that synchronization occurs. The dominant vorticity shedding pattern found was the so-called 2P mode. However, a significant difference was found when compared to the free-stream situation. While in the former, the two vorticity regions that make up the 2P pair come from the prism, in the present confined case, one came from the prism, and the other came from the wall. Another difference was that in the present case, the 2P pairs were much more elongated than in the free stream case, and this had a significant influence on the stretching and bending of streak lines and, therefore, on mixing.

Practical implications

The study that has been presented has a practical industrial implication for the processes industry because it provides guidelines to design active mixers that deal with aqueous power law polymeric solutions. In parallel, it opens up some new research lines in the direction of studying whether the mixing concept might be modified so as to develop a fully passive system that could be far simpler and, possibly, more attractive to industry.

Originality/value

The originality and value of the study are associated to the systematic approach that has been followed. It has allowed to establish a clear pattern regarding the active mixing behavior of HEC solutions in confined flows. To the best of authors’ knowledge, this could be the first study of this type in the literature. Also, the study has contributed to understand the vorticity shedding patterns that appear in these types of problems and how they shape wake topology and, consequently, mixing performance. The finding that optimum mixing requires synchronization of stirring motion frequency and wake first natural frequency of instability may help to improve the design and operation of industrial mixers dealing with polymeric aqueous solutions.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 33 no. 3
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 17 October 2022

Nacim Alilat, Elena B. Martin, Francisco Sastre, Jose Antonio Millán García and Abderrahmane Baïri

The aim of this work is to determine the average surface temperature of a conical antenna. Its cooling is ensured by means of a nanofluid-saturated porous structure. The volume…

84

Abstract

Purpose

The aim of this work is to determine the average surface temperature of a conical antenna. Its cooling is ensured by means of a nanofluid-saturated porous structure. The volume fraction of the H2O–Cu nanofluid ranges between 0% (pure water) and 5%, whereas the ratio between the thermal conductivity of the used porous materials and that of water (fluid base) varies in the wide 4–41.2 range. The antenna is contained in a coaxial conical closed cavity with a variable distance between the cones, leading to an aspect ratio varying between 0.2 and 0.6. The axis of the assembly is also inclined with respect to the gravity field by an angle varying between 0° (a vertical axis with top of the cone oriented upwards) and 180° (a vertical axis with top of the cone oriented downwards).

Design/methodology/approach

Simulations have been done by means of the volume control method based on the SIMPLE algorithm.

Findings

Results of the numerical approach show that the cavity’s aspect ratio and inclination with respect to the gravity field significantly affect the thermal behavior of the active cone. Otherwise, the work confirms that the Maxwell and Brinkman models used to determine the nanofluid’s effective thermal conductivity and viscosity, respectively, are adapted to the considered assembly.

Originality/value

A new correlation is proposed, allowing the determination of the average surface temperature of the active cone and its correct thermal sizing. This correlation could be used in various engineering fields, including electronics, examined in the present study.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 32 no. 12
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 25 August 2021

Francisco Sastre, Elena B. Martin, Angel Velazquez and Abderrahmane Baïri

This paper aims to compare the performance of flow pulsation versus flow stirring in the context of mixing of a passive scalar at moderate Reynolds numbers in confined flows. This…

163

Abstract

Purpose

This paper aims to compare the performance of flow pulsation versus flow stirring in the context of mixing of a passive scalar at moderate Reynolds numbers in confined flows. This comparison has been undertaken in two limits: diffusion can be neglected as compared to convection (very large Peclet) and diffusion and convection effects are comparable. The comparison was performed both in terms of global parameters: pumping power and mixing efficiency and local flow topology.

Design/methodology/approach

The study has been addressed by setting up a common conceptual three-dimensional problem that consisted of the mixing of two parallel streams in a square section channel past a square section prism. Stirring and pulsation frequencies and amplitudes were changed and combined at an inlet Reynolds number of 200. The numerical model was solved using a finite volume formulation by adapting a series of open-source OpenFOAM computational fluid dynamic (CFD) libraries. For cases with flow pulsation, the icoFoam solver for laminar incompressible transient flows was used. For cases with stirring, the icoDyMFoam solver, which uses the arbitrary Lagrangian–Eulerian method for the description of the moving dynamical mesh, was used to model the prism motion. At the local flow topology level, a new method was proposed to analyze mixing. Time evolution of folding and wrinkling of sheets made up of virtual particles that travel along streak lines was quantified by generating lower rank projections of the sheets onto the spaces spanned by the main eigenvectors of an appropriate space-temporal data decomposition.

Findings

In the limit when convection is dominant, the results showed the superior performance of stirring versus flow pulsation both in terms of mixing and required pumping power. In the cases with finite Peclet, the mixing parameters by stirring and flow pulsation were comparable, but pulsation required larger pumping power than stirring. For some precise synchronization of stirring and pulsation, the mixing parameter reached its maximum, although at the expense of higher pumping power. At the local flow topology level, the new method proposed to quantify mixing has been found to correlate well with the global mixing parameter.

Originality/value

A new systematic comparative study of two methods, stirring and pulsation, to achieve mixing of passive scalars in the mini scale for confined flows has been presented. The main value, apart from the conclusions, is that both methods have been tested against the same flow configuration, which allows for a self-consistent comparison. Of particular interest is the fact that it has been found that accurate synchronization of both methods yields mixing parameters higher than those associated to both methods taken separately. This suggests that it is possible to synchronize mixing methods of a different nature to achieve optimum designs. The new theoretical method that has been proposed to understand the mixing performance at the local level has shown promising results, and it is the intention of the authors to test its validity in a broader range of flow parameters. All these findings could be taken as potential guidelines for the design of mixing processes in the mini scale in the process industry.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 32 no. 6
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 19 June 2009

Wineaster Anderson, Catalina Juaneda and Francisco Sastre

This paper aims to identify the motivations for choosing all‐inclusive package tours when traveling, and to specify the visitor and travel attributes associated with those…

3706

Abstract

Purpose

This paper aims to identify the motivations for choosing all‐inclusive package tours when traveling, and to specify the visitor and travel attributes associated with those motivations.

Design/methodology/approach

A specific visitor‐exit‐survey involving all‐inclusive tourists visiting the Balearic Islands (n=843) was conducted during the summer of 2006 at the Airport of Palma de Mallorca. Then, through discrete choice models‐binary logit, relationships between the identified motivations and specified attributes were analyzed by looking for the attributes that are more associated with each motive.

Findings

The study results show that tourists traveling through all‐inclusive tours attach more importance to the motivations related to convenience and relaxation, economies of resources as well as safety and security in their vacationing processes; with specific tourist and trip attributes influencing the probability for confirmation.

Practical implications

Understanding the motivation of different tourist profiles visiting the destinations is useful in managing the tourism industry for satisfying specific tourist segments without jeopardizing the interests of the host community. A full understanding of all‐inclusive motivation would help travel organizers and marketers to plan, design and deliver products and services that cater for the specific needs of the all‐inclusive market, with the aim of capturing the financial benefits which are the central element of the economy.

Originality/value

There is still little knowledge in the literature about all‐inclusive package tourism. Specifically, the knowledge of tourist motivation with reference to the tour mode choice within the tourism landscape is still diluted, and therefore the motive behind one traveling through certain tour modes like all‐inclusives continues to miss the ground works. Nor have the factors that influence evaluation of the motivations related to the decision of this type of trip have been much studied, which renders this field of study one of the underdeveloped areas in the tourism social sciences. The paper attempts to contribute where there is this lack of knowledge.

Details

Tourism Review, vol. 64 no. 2
Type: Research Article
ISSN: 1660-5373

Keywords

Available. Content available
Article
Publication date: 19 June 2009

Thomas Bieger and Christian Laesser

315

Abstract

Details

Tourism Review, vol. 64 no. 2
Type: Research Article
ISSN: 1660-5373

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Book part
Publication date: 3 November 2005

Pamela H. Wescott, Ellen J. Reifler, Karen Sepucha and Elyse R. Park

Disparities in health care for underserved populations have raised questions about the quality of decisions made by these patients. We explored the decision-making experiences and…

Abstract

Disparities in health care for underserved populations have raised questions about the quality of decisions made by these patients. We explored the decision-making experiences and reactions to a decision aid in focus groups of African American, Hispanic, and Rural breast cancer survivors. All groups were taped, transcribed, and thematic analysis was performed. Individual differences were more common than differences among demographic groups. Decision aids appear to be acceptable without extensive targeting to specific groups. However, translating the decision aid would increase its usefulness for Hispanic populations.

Details

Health Care Services, Racial and Ethnic Minorities and Underserved Populations: Patient and Provider Perspectives
Type: Book
ISBN: 978-0-76231-249-8

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Article
Publication date: 15 October 2020

Juan Alberto Hueso, Inmaculada Jaén and Francisco Liñán

This systematic literature review (SLR) analyses the existing contributions, jointly studying personal values (PVs) and intentions in entrepreneurship. Despite the long tradition…

2908

Abstract

Purpose

This systematic literature review (SLR) analyses the existing contributions, jointly studying personal values (PVs) and intentions in entrepreneurship. Despite the long tradition that these two constructs enjoy in social psychology, they have only recently been considered together in entrepreneurship research.

Design/methodology/approach

To conduct this SLR, three widely used databases were searched (Scopus, ABI-INFORM and Web of Science). A total of 451 initial hits were successively narrowed down to a final list of 22 journal articles matching the inclusion criteria. This field of research is very recent since the selected papers have all been published since 2011, half of which have appeared since 2017.

Findings

The predominant approach in these papers was the consideration of PVs as antecedents in the formation of entrepreneurial intentions (EIs). In particular, basic human values (BHV) theory for PVs and the theory of planned behaviour (TPB) for intentions are the prevalent frameworks. The influence of PVs differs notably depending on the motivational antecedent of intention being considered and also on the specific (general vs social) EI analysed.

Originality/value

This SLR is, to the best of the authors’ knowledge, the first review that addresses this fast-growing area of research. It provides a comprehensive mapping of the contributions to date as well as an integrative conceptual framework to synthetise accumulated knowledge. It also identifies subsisting knowledge gaps and a number of future research opportunities.

Details

International Journal of Entrepreneurial Behavior & Research, vol. 27 no. 1
Type: Research Article
ISSN: 1355-2554

Keywords

Available. Content available
Article
Publication date: 9 November 2012

María Teresa Méndez Picazo

506

Abstract

Details

Management Decision, vol. 50 no. 10
Type: Research Article
ISSN: 0025-1747

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Article
Publication date: 1 January 2003

Santiago García González, Ana Gessa Perera and Francisco Aguado Correa

Firms are increasingly aware of environmental degradation and this has led many of them to include “quality, safety and protecting the environment” among their competitive…

1445

Abstract

Firms are increasingly aware of environmental degradation and this has led many of them to include “quality, safety and protecting the environment” among their competitive priorities. This also involves large capital investments aimed at reducing the environmental impact of their manufacturing activities. This study suggests a method for estimating the return of manufacturing investments with environmental effects (costs and benefits). It considers the value of the asset being preserved as a consequence of a firm’s social responsibility. The practical case studied is Huelva’s industrial area.

Details

International Journal of Operations & Production Management, vol. 23 no. 1
Type: Research Article
ISSN: 0144-3577

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Article
Publication date: 11 June 2018

Alberto Javier Báez-García, Francisco Flores-Muñoz and Josué Gutiérrez-Barroso

The main purpose of this paper is to contribute to the ongoing literature on the pertinence of TALC (tourism area life cycle) to model and analyse mature destinations, using…

580

Abstract

Purpose

The main purpose of this paper is to contribute to the ongoing literature on the pertinence of TALC (tourism area life cycle) to model and analyse mature destinations, using quantitative data and alternative functional forms. With this purpose, this work analyses the recent data on tourist demand in Tenerife (Canary Islands), which is supposed to be playing the role of “refuge” with respect to other competing resorts, when the latter ones present political instability after the so-called Arab Springs, particularly the Middle East and North Africa.

Design/methodology/approach

To analyse the data, and to explore potential epiphenomenon, nonlinear competing regression analysis were performed (logistic, Gaussian and logarithmic), taking into account some insights from tourism life cycle theories.

Findings

Some suggestions are presented for political management of these destinations that are still working under a moratorium on tourist infrastructure.

Research limitations/implications

Once the TALC is accepted – even under discussion – in the scholarly fore, certain incentives arise to identify, interpret and communicate signals of maturity. Public funds and specific policies (moratoria) can then be solicited to political instances. Further empirical research, complementary quantitative approaches, along with new data that confronts the evolution of demand in Tenerife with paulatine reactivation of competing destinations, will be strongly required to overcome the limitations of this first attempt and to properly determine the effectiveness of rejuvenation policies. Besides, additional quantitative data should be considered to explore the potential explanatory factors beyond the time series analysis into models that are more theoretical.

Originality/value

The results suggest that the diagnosis of maturity was at least premature in the first place, poorly based on data analysis and fast in promoting specific policies whose effectiveness is under discussion even after decades.

Details

Tourism Review, vol. 73 no. 3
Type: Research Article
ISSN: 1660-5373

Keywords

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