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…
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
Keywords
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…
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
Keywords
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…
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
Keywords
David Martín-Moncunill, Miguel Angel Sicilia-Urban, Elena García-Barriocanal and Christian M. Stracke
The common understanding of generalization/specialization relations assumes the relation to be equally strong between a classifier and any of its related classifiers and also at…
Abstract
Purpose
The common understanding of generalization/specialization relations assumes the relation to be equally strong between a classifier and any of its related classifiers and also at every level of the hierarchy. Assigning a grade of relative distance to represent the level of similarity between the related pairs of classifiers could correct this situation, which has been considered as an oversimplification of the psychological account of the real-world relations. The paper aims to discuss these issues.
Design/methodology/approach
The evaluation followed an end-user perspective. In order to obtain a consistent data set of specialization distances, a group of 21 persons was asked to assign values to a set of relations from a selection of terms from the AGROVOC thesaurus. Then two sets of representations of the relations between the terms were built, one according to the calculated concept of specialization weights and the other one following the original order of the thesaurus. In total, 40 persons were asked to choose between the two sets following an A/B test-like experiment. Finally, short interviews were carried out after the test to inquiry about their decisions.
Findings
The results show that the use of this information could be a valuable tool for search and information retrieval purposes and for the visual representation of knowledge organization systems (KOS). Furthermore, the methodology followed in the study turned out to be useful for detecting inconsistencies in the thesaurus and could thus be used for quality control and optimization of the hierarchical relations.
Originality/value
The use of this relative distance information, namely, “concept specialization distance,” has been proposed mainly at a theoretical level. In the current experiment, the authors evaluate the potential use of this information from an end-user perspective, not only for text-based interfaces but also its application for the visual representation of KOS. Finally, the methodology followed for the elaboration of the concept specialization distance data set showed potential for detecting possible inconsistencies in KOS.
Details
Keywords
Elena Bárcena-Martin and Jacques Silber
This chapter shows that the algorithm recently proposed to decompose the Foster and Wolfson bipolarization index by income sources (see Bárcena-Martin, Deutsch, & Silber…
Abstract
This chapter shows that the algorithm recently proposed to decompose the Foster and Wolfson bipolarization index by income sources (see Bárcena-Martin, Deutsch, & Silber, forthcoming) may be extended to break down wage bipolarization by its determinants. The chapter gives an empirical illustration comparing the determinants of wage bipolarization and inequality in various European countries in 2011, with a special focus on Portugal. In Portugal higher levels of education are the main source of bipolarization and inequality. Gender and working in the public sector are important determinants of bipolarization while age and having a temporary job are important determinants of inequality.
Details
Keywords
Babak Panahi, Elena Moezzi, Christopher Nigel Preece and Wan Normeza Wan Zakaria
The possible effect of conflicts as the consequence of differences between personal and organizational values (OV) on organizational commitment (OC) of internal construction…
Abstract
Purpose
The possible effect of conflicts as the consequence of differences between personal and organizational values (OV) on organizational commitment (OC) of internal construction stakeholders was an unclear issue in the areas of organizational behaviour in the construction industry, especially in Malaysia. Therefore, the purpose of this paper is to focus on this issue in the Malaysian construction industry.
Design/methodology/approach
This paper targeted professional project consultants, who are identified as architects, engineers, and quantity surveyors, as the internal construction stakeholders. The personal-OV and the level of OC of the stakeholders were evaluated through a questionnaire survey. To achieve the research objective, comparative and hierarchical regression analyses were performed.
Findings
The results generated by the analyses indicated a high level of value conflicts in the construction organizations which significantly and negatively affected commitment of the internal stakeholders.
Originality/value
Value conflicts in construction organizations are the agenda of this paper while not many empirical studies have been conducted on this issue in Malaysia. This paper through investigating the potential effect of value conflicts on the stakeholders’ commitment reveals the importance of interaction between personal and OV in construction organizations which contributes to the extant literature of organizational behaviour as to the construction literature.
Details
Keywords
Nataliya Perevoshchikova, Jordan Rigaud, Yu Sha, Martin Heilmaier, Barrie Finnin, Elena Labelle and Xinhua Wu
The Ni-based superalloy IN-738 LC is known to be susceptible to porosity and different types of cracking during the build-up process and, thus, challenging to manufacture using…
Abstract
Purpose
The Ni-based superalloy IN-738 LC is known to be susceptible to porosity and different types of cracking during the build-up process and, thus, challenging to manufacture using selective laser melting (SLM). Determining a feasible set of operating parameters for SLM of nickel-based superalloys involves new approach to experimental design based on the Doehlert method that assists in determining an optimal (feasible) set of operating parameters for SLM of IN-738 LC powder alloy.
Design/methodology/approach
The SLM parameters are evaluated in terms of their effectiveness in obtaining the microstructure with a porosity content of <0.5 per cent and without micro-cracking. The experimental approach is exemplified with the Doehlert matrix response variable, relative density, by comparing Archimedes method with microstructural assessments of pores and cracks from image analysis. The effect of heat treatment (HT) and hot isostatic pressing (HIP) on the microstructure of the SLMed IN-738 LC powder alloy has been examined and the consequential tensile response characterised.
Findings
By using optimised process parameters (low heat input, medium scanning speed and small hatching distance) which provides medium energy density, samples of IN-738 LC with a macroscopic porosity <0.5 per cent and free of micro-cracks can be manufactured by SLM. The results indicate that HIP of SLMed material did not lead to a noticeable effect on mechanical properties compared to HT of SLMed material suggesting that the level of both porosity and crack density might be already below the detection limit for the mere heat-treated material.
Originality/value
SLM processing parameters (power, scan speed, hatching distance) for IN-738 LC were successfully optimised after only 14 experiments using Doehlert design. Two independent methods, Archimedes method and image analysis, were used in this study to assess relative density of SLM-produced samples with sets of processing parameters showing coherency in prediction with predicted response by Doehlert design.
Details
Keywords
Elena V. Susimenko, Galina V. Shevtsova, Svetlana V. Rozhdestvenskaya, Elena B. Narochnaya and Anastasia A. Popova
The specific character of language policy is considered in multi-ethnic Russian regions in this paper. The relevance of this paper is because of the fact that language is one of…
Abstract
Purpose
The specific character of language policy is considered in multi-ethnic Russian regions in this paper. The relevance of this paper is because of the fact that language is one of the most important indicators of ethnic identity, and it fulfills a crucial role in the self-preservation of the ethnic community. The purpose of this paper is to determine the status and trends of language policy in multi-ethnic regions as a part of national education.
Design/methodology/approach
The authors analyze the historical aspect of language policy with the help of problem and comparative analysis and study the problem of bilingualism in the modern Russian society.
Findings
The threat of loss or the ban on land national (mother) language, as well as its infringement form an intolerant consciousness and attitudes in the mass consciousness and behavior of people. It is one of the factors of the deterioration of interethnic interaction and increase of ethnocentric attitudes to counter assimilation and acculturation. Language has communicative, integration, political functions in modern society. It is very important for the preservation of ethnic education. The analysis shows the inconsistency in the language policy whose roots lie in the historical past.
Originality/value
It is substantiated that the existence of a variety of peoples, ethnic groups with their own independent languages challenge state government bodies to solve a number of problems associated with ensuring the optimal functioning of Russian and national (mother) languages. It is concerned with the quality of education in the education system and the advisability of using languages in official events and the volume of television and radio programs in national languages, and so on.
Details
Keywords
Ismael San Mauro Martin, Juanjo Nava Mateo, Jesús Ortiz Rincón, Marta Villanueva Nieto, Elena Ávila Díaz, Sara Sanz Rojo, Licia de la Calle, Yaiza Quevedo Santos, Paloma Elortegui Pascual, Víctor Paredes Barato, Sara López Oliva and Elena Garicano Vilar
The world’s aging population has led to a greater use of prescription and non-prescription medication by the elderly. Besides, older drinkers consume alcohol often regardless of…
Abstract
Purpose
The world’s aging population has led to a greater use of prescription and non-prescription medication by the elderly. Besides, older drinkers consume alcohol often regardless of the medication they consume. The purpose of this paper is to examine the intake of medication and alcohol simultaneously in a group of elderly in the community of Madrid, and the possible differences in consumption between men and women.
Design/methodology/approach
An observational cross-sectional study of 342 elderly in Madrid, aged 65–96 years was conducted, including the collection of anthropometric data (weight, height, waist circumference, BMI), information about the quantity of daily alcohol intake and medication taken from each subject.
Findings
A high percentage of the sample used medication, especially women. A smaller percentage of the sample consumed alcohol, being more frequent among men and decreasing with age. In addition, almost half of the sample (46.4 percent) combined medication intake with alcohol, especially men. High alcohol consumption was observed simultaneously in those subjects taking medication; in addition to the non-perception of the real risk to health. Statistically significant sex differences were observed, since men drank more, including when taking medication; although women may be more vulnerable to harm derived from alcohol.
Originality/value
This study contributed to estimate the risk to the public health of old people, and the integrity of their health, by observing the consumption of both medication and alcohol, given that medication taken in conjunction with alcohol can cause adverse side effects.
Details
Keywords
Olga A. Chernikova, Egor V. Dudukalov, Elena Yu. Zolochevskaya and Ekaterina A. Popova
The purpose of this research is to substantiate the processes of implementing the electronic forms of business integration under the conditions of digital transformation by market…
Abstract
Purpose
The purpose of this research is to substantiate the processes of implementing the electronic forms of business integration under the conditions of digital transformation by market players.
Design/Methodology/Approach
The methods used in this research include cooperative game theory, systemic analysis and statistical analysis.
Findings
This research presents the substantiation of the processes of implementing the electronic forms of business integration under the conditions of digital transformation by market players. The proprietary methodology of evaluation of the set problems includes three procedures: analysis of the electronic forms of business integration that are used in the digital economy in the world, which envisages their systematisation; evaluation of the effectiveness of implementing the processes of business integration with the use of such forms and their forecast estimation under the condition of individual development of the market environment's players, as well as determination of advantages; and development of the practical implications for managing the electronic forms of business integration for the national companies of developing countries (with forecasting based on the cooperative game theory). The modern electronic forms of business integration include electronic cash (e-cash), electronic data interchange, electronic banking (e-banking), electronic marketing (e-marketing), electronic insurance (e-insurance) and electronic trade (e-trade). Analysis of the effectiveness of implementing the processes of business integration with the use of the electronic forms is performed based on electronic trade, which is used under the conditions of the functioning of digital trade platforms (Internet stores). Such digital trade platforms, as the forms of business strategies, are Amazon and eBay Inc. These two American companies were selected because the United States has the leading position in this sphere. The comparative analysis showed the advantages of participation of players in partnership with the use of electronic trade within two digital platforms, connected to cost saving on advertising and organisation of trade. The practical implications of implementing the electronic forms of business integration for the national companies of developing countries are also presented; they are formed based on the practice of implementing the advantages revealed in the activities of the digital trade platforms Amazon and eBay Inc.
Originality/Value
The originality and value of this research are due to the further development of provisions on the specifics of the process of implementing the electronic forms of business integration under the conditions of digital transformation by market players.