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Article
Publication date: 2 November 2015

Mouna Gazzah, Boubaker Jaouachi, Laurence Schacher, Dominique Charles Adolphe and Faouzi Sakli

The purpose of this paper is to predict the appearance of denim fabric after repetitive uses judging the denim cloth behavior and performance in viewpoint of bagging…

Abstract

Purpose

The purpose of this paper is to predict the appearance of denim fabric after repetitive uses judging the denim cloth behavior and performance in viewpoint of bagging ability. Hence, it attempts to carry out the significant inputs and outputs that have an influence on the bagging behaviors using the Principal Component Analysis (PCA) technique. In this study, the Kawabata Evaluation System parameters such as the frictional characteristics, the bending, compression, tensile and shear parameters are investigated to propose a model highlighting and explaining their impacts on the different bagging properties. To improve the obtained results, the selected significant inputs are also analyzed within their bagging properties using Taguchi experimental design. The linear regressive models prove the effectiveness of the PCA method and the obtained findings.

Design/methodology/approach

To investigate the mechanical properties and their contributions on the bagging characteristics, some denim fabrics were collected and measured thanks to the Kawabata evaluation systems (KES-FB1, KES-FB2, KES-FB3 and KES-FB4). These bagging properties were further analyzed applying the method of PCA to acquire factor patterns that indicate the most important fabric properties for characterizing the bagging behaviors of different studied denim fabric samples. An experimental design type Taguchi was, hence, applied to improve the results. Regarding the obtained results, it may be concluded that the PCA method remained a powerful and flawless technique to select the main influential inputs and significant outputs, able to define objectively the bagging phenomenon and which should be considered from the next researches.

Findings

According to the results, there are good relationships between the Kawabata input parameters and the analyzed bagging properties of studied denim fabrics. Indeed, thanks to the PCA, it is probably easy to reduce the number of the influent parameters for three reasons. First, applying this technique of selection can help to select objectively the most influential inputs which affect enormously the bagged fabrics. Second, knowing these significant parameters, the prediction of denim fabric bagging seems fruitful and can undoubtedly help researchers explain widely this complex phenomenon. Third, regarding the findings mentioned, it seems that the prevention of this aesthetic phenomenon appearing in some specific zones of denim fabrics will be more and more accurate.

Practical implications

This study is interesting for denim consumers and industrial applications during long and repetitive uses. Undoubtedly, the denim garments remained the largely used and consumed, hence, this particularity proves the necessity to study it in order to evaluate the bagging phenomenon which occurs as function of number of uses. Although it is fashionable to have bagging, the denim fabric remains, in contrast with the worsted ones, the most popular fabric to produce garments. Moreover, regarding this characteristic, the large uses and the acceptable value of denim fabrics, their aesthetic appearance behavior due to bagging phenomenon can be analyzed accurately because compared to worsted fabrics, they have a high value and the repetitive tests to investigate widely bagged zones may fall the industrial. The paper has practical implications in the clothing appearance and other textile industry, especially in the weaving process when friction forms (yarn-to-yarn, yarn-to-metal frictions) and stresses are drastic. This can help understanding why residual bagging behavior remained after garment uses due to the internal stress and excessive extensions. Regarding the selected influential inputs and outputs relative to bagging behaviors, there are some practical implications that have an impact on the industrial and researchers to study objectively the occurrence of this aesthetic phenomenon. Indeed, this study discusses the significance of the overall inputs; their contributions on the denim fabric bagged zones aims to prevent their ability to appear after uses. Moreover, the results obtained regarding the fabric mechanical properties can be useful to fabric and garment producers, designers and consumers in specifying and categorizing denim fabric products, insuring more denim cloth use and controlling fabric value. For applications where the subjective view of the consumer is of primary importance, the KES-FB system yields data that can be used for evaluating fabric properties objectively and prejudge the consumer satisfaction in viewpoint of the bagging ability. Therefore, this study shows that by measuring shear, tensile and frictional parameters of KES-FB, it may be possible to evaluate bagging properties. However, it highlights the importance and the significance of some inputs considered influential or the contrast (non-significant) in other researches.

Originality/value

This work presents the first study analyzing the bagged denim fabric applying the PCA technique to remove the all input parameters which are not significant. Besides, it deals with the relationship developed between the mechanical fabric properties (tensile, shear and frictional stresses) and the bagging properties behavior. To improve these obtained relationships, for the first time, the regression technique and experimental design type Taguchi analysis were both applied. Moreover, it is notable to mention that the originality of this study is to let researchers and industrials investigate the most influential inputs only which have a bearing on the bagging phenomenon.

Details

International Journal of Clothing Science and Technology, vol. 27 no. 6
Type: Research Article
ISSN: 0955-6222

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Article
Publication date: 1 November 2014

M. Gazzah and B. Jaouachi

This work deals with the evolution of the residual bagging height of knitted samples. In comparing the results after a fabric bagging test, it may be concluded that the…

Abstract

This work deals with the evolution of the residual bagging height of knitted samples. In comparing the results after a fabric bagging test, it may be concluded that the behaviour of the sample length is an influential parameter which widely reflects the anisotropy of knitted structures. Hence, it is clear that the sample length does not exhibit the same behaviour in each knitted fabric zone which generally explains the impartial response after stress is applied. With regards to the different height values that the sample length presents in each measured part of the fabric, it may be concluded that there are several types of behaviours in the areas of bagging along the sample length. Moreover, it appears that there is a non uniform distribution of deformation after removing the stress. Therefore, internal stresses and deformations that cause different residual heights in the same sample accurately reflect and explain the anisotropic structure of the investigated knitted fabrics. In knowing that there is this non-uniform distribution of deformation, the input parameters also have considerable effects on the bending behaviour of the residual bagging. Indeed, when the yarn structure is changed, the residual bagging height changes too. Furthermore, our findings prove that elastic knitted fabrics accurately show a more minimal residual bagging height as opposed to non elastic fabrics in spite of the other input parameter values.

Details

Research Journal of Textile and Apparel, vol. 18 no. 4
Type: Research Article
ISSN: 1560-6074

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Article
Publication date: 6 June 2016

Senda Agrebi, Juan P. Solano, Ali Snoussi and Ammar Ben Brahim

The purpose of this paper is to present a numerical analysis of the flow and heat transfer in a tube with a wire coil insert. A second law analysis of the results is…

Abstract

Purpose

The purpose of this paper is to present a numerical analysis of the flow and heat transfer in a tube with a wire coil insert. A second law analysis of the results is accounted for, in order to assess the local and overall entropy generation in relation with the increased pressure drop and convective heat transfer. A wire coil with p/D=1.25 and e/D=0.076 is selected as insert device. A Reynolds number range between 100 and 1,000 is investigated, which corresponds to the typical operating regimes in the risers of liquid solar collectors. Different wall heat fluxes and inclination angles allow to analyze the potential impact of mixed convection in the presence of tube inserts.

Design/methodology/approach

Three-dimensional numerical simulations are performed using a finite-volume solver, assuming laminar flow conditions. Pure water and a mixture of water and propylene-glycol (20 percent) are used as working fluids, with temperature-dependent properties. Fanning friction factor, Nusselt number and local entropy generation results are obtained in the fully developed region.

Findings

The friction factor results are successfully compared with a well-known experimental correlation for wire coil inserts. The earlier onset of transition is devised at Re > 300. Nusselt number augmentations between 2.5- and 6-fold are reported with respect to the smooth tube. The mixed convection regime encountered in the smooth tube for the operating conditions investigated is canceled in the wire coiled tube, owing to the opposed effect of the swirl flow induced and the bouyancy forces. Frictional, heat transfer and overall entropy generation rates are computed locally in the fully developed region, allowing to relate these results with the flow structures in the mixed convection smooth tube and in the wire coiled tube. A threefold decrease in the entropy generation rate is reported for tubes with wire coil inserts.

Originality/value

An holistic understanding of the heat transfer enhancement in tubes with wire coil inserts is provided through the analysis of the flow pattern, Fanning friction factor, Nusselt number and local entropy generation rates. The reduced entropy generation in the enhanced tube serves as a performance criteria to confirm the positive effect of wire coil inserts in heat transfer for the operating regime under investigation, in spite of the increased pressure drop.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 26 no. 5
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 3 May 2016

Andrzej J Nowak, Michal Palacz, Jacek Smolka, Krzysztof Banasiak, Zbigniew Bulinski, Adam Fic and Armin Hafner

The purpose of this paper is to overview successful approaches to the computational simulation of real fluid (R744 – carbon dioxide (CO2)) flow within an ejector is…

Abstract

Purpose

The purpose of this paper is to overview successful approaches to the computational simulation of real fluid (R744 – carbon dioxide (CO2)) flow within an ejector is presented. Important issues such as the ejector geometry and its optimisation, the adapted equations of state and the proposed models of the process, fluid parameters, etc., are examined and critically discussed. Whenever possible, the discussed models are experimentally validated. In the conclusion, some trends in future research are pointed out.

Design/methodology/approach

Flow within CO2 ejector is generally transcritical and compressible. Models existing in the literature are shortly described and critically compared. Whenever possible, those models were validated against the experimental data. In a model validation process, the primary and secondary mass flow rates as well as the pressures at the selected points in the mixing section and diffuser were compared, showing a satisfactory agreement between experimental and computational results.

Findings

Developed CO2 ejector flow models are tested in few industrial applications. All these initiatives bring solutions which are interesting and very promising from technological point of view.

Originality/value

This is an extensive overview of successful approaches to computational simulation of the real fluid (R744 – CO2) flow within ejector. It brings many useful information.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 26 no. 3/4
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 23 July 2018

Michał T. Lewandowski, Paweł Płuszka and Jacek Pozorski

This paper aims to assess the sensitivity of numerical simulation results of turbulent reactive flow to the formulation of inlet boundary conditions. The analysis concerns…

Abstract

Purpose

This paper aims to assess the sensitivity of numerical simulation results of turbulent reactive flow to the formulation of inlet boundary conditions. The analysis concerns the profiles of the mean velocity the turbulence kinetic energy k and its dissipation rate ϵ. It is intended to provide guidance to the determination of inlet conditions when only global flow data are available. This situation can be met both in simple laboratory experiments and in industrial full-scale applications, when measurements are either incomplete or infeasible, resulting in lack of detailed inlet data.

Design/methodology/approach

Two turbulence–chemistry interaction models were studied: eddy dissipation concept and partially stirred reactor. Three different velocity profiles and related turbulence statistics were applied to present feasible scenarios and their consequences. Simulations with the most appropriate inlet data were accompanied with profiles of turbulent quantities obtained with a proposed method. This method was contrasted to other approaches popular in the literature: the pre-inlet pipe and the separate cold flow simulations of a burner. The methodology was validated on two laboratory-scale jet flames: Delft Jet-in-Hot-Coflow and Sandia CHN B. The simulations were carried out with open source code OpenFOAM.

Findings

The proposed relations for turbulence kinetic energy and its dissipation rate at the inlet are found to provide results comparable to those obtained with the use of experimental data as inlet boundary conditions. Moreover, from a certain location downstream the jet, weakly dependent on the Reynolds number, the influence of inlet conditions on flow statistics was found to be negligible.

Originality/value

This work reveals the consequences of the use of rather crude assumptions made for inlet boundary conditions. Proposed formulas for the profiles for k and epsilon are attractive alternatives to other approaches aiming to determine the inlet boundary conditions for turbulent jet flows.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 6
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 7 June 2013

Mouna Feki, Hédia Hannachi, Moez Bou Ali, Haytem Hamrouni, Elvira Romano, Boubaker Karray and Mohamed Hammami

The purpose of this paper is to build a class model to confirm the authenticity of olives from Bi'r al Malluli, Tunisian region, in order to obtain the Designation of Origin (DO).

Abstract

Purpose

The purpose of this paper is to build a class model to confirm the authenticity of olives from Bi'r al Malluli, Tunisian region, in order to obtain the Designation of Origin (DO).

Design/methodology/approach

In total, ten orchards of Chemlali olive oil variety were chosen, in Sfax region, characterized by the same applied cultural techniques. Pomological characters of olives, fatty acids composition and organoleptic analysis of olive oil were conducted.

Findings

Results showed that the pomological characters were specific of the Chemlali variety: the olive weight ranged from 0.9 to 1.10 g in all studied orchards and the water content (WC) ranged from 41.45 to 57.68 per cent. All analysed oils showed good fatty acids balance. Chemlali olive oil contains high amounts of oleic acid and a smaller amount of linoleic acid. The oleic acid content ranged from 57.96 to 63.52 per cent according to the orchards. All oils having oleic acid higher than 55 per cent are categorized as extra virgin olive oil based on International Olive Oil Council (IOOC) Norma. Based on the organoleptic analysis, all the analysed oils were classified as an extra virgin olive oil. The principal component analysis applied separately on olive characters and fatty acids contents do not indicate any group's structure.

Originality/value

An objective approach based on pomologic, sensory and acidic composition analyses would be used to delimitate Protected Designation of Origin (PDOs) in olive oil from the Bi'r al Malluli area and better protect their markets.

Details

British Food Journal, vol. 115 no. 6
Type: Research Article
ISSN: 0007-070X

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Article
Publication date: 11 July 2016

Paula Correia, André Vítor, Marlene Tenreiro, Ana Cristina Correia, João Madanelo and Raquel Guiné

Thistle flower (Cynara cardunculus) aqueous extracts, as rich source of milk-clotting peptidases, have been widely used for cheeses marketed under the Registry of the…

Abstract

Purpose

Thistle flower (Cynara cardunculus) aqueous extracts, as rich source of milk-clotting peptidases, have been widely used for cheeses marketed under the Registry of the Protected Designation of Origin, as it is the case of Serra da Estrela cheese, manufactured from raw ewes’ milk and without addition of any commercial starter culture. This paper aims at studying the influence of six different ecotypes of thistle flowers in cheese properties during the ripening and of final products.

Design/methodology/approach

Cheeses were produced with different thistle flower extracts and then the clotting time, weight and colour of cheeses, as well as texture properties and sensorial characteristics, were evaluated.

Findings

The clotting time varied from 47 to 66 min, and the weight loss along ripening varied between 32 and 40 per cent. There was some influence of thistle flower ecotype on the colour during ripening and in the final product. The results of texture analysis revealed significant differences between the thistle ecotypes: crust firmness varying from 2.4 to 5.6 N; inner firmness from 0.82 to 1.82 N; stickiness from −0.5 to −1.60 N; adhesiveness from −3.0 to −11.3 N.s; and Ecotype C was particularly distinguishable. Sensorial evaluation revealed differences among the cheeses, with Ecotype C receiving the highest score for global appreciation.

Originality/value

The usage of different extracts of thistle flower to produce Serra da Estrela cheese with different properties is a novelty, and it allows the possibility of manipulating this parameter in the future so as to produce cheeses with specific characteristics, addressed to different consumer targets.

Details

Nutrition & Food Science, vol. 46 no. 4
Type: Research Article
ISSN: 0034-6659

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Article
Publication date: 7 August 2009

Keivan Khademi Shamami and Madjid Birouk

This paper aims to describe the numerical simulation of a three‐dimensional turbulent free jet issuing from a sharp‐edged equilateral triangular orifice into still air.

Abstract

Purpose

This paper aims to describe the numerical simulation of a three‐dimensional turbulent free jet issuing from a sharp‐edged equilateral triangular orifice into still air.

Design/Methodology/approach

The numerical simulation was carried out by solving the governing three‐dimensional Reynolds‐averaged Navier‐Stokes equations. Several two‐equation eddy‐viscosity models (i.e. the standard k‐ε, renormalization group (RNG) k‐ε, realizable k‐ε, shear‐stress transport (SST) k‐ω), as well as the Reynolds stress models (i.e. the standard RSM and the SSG) were tested to simulate the flowfield. The numerical predictions were compared with experimental data in order to assess the capability and limitations of the various turbulent models examined in this work. Findings –The vena contracta effect was predicted by all the tested models. Among the eddy‐viscosity models only the realizable k‐ε model showed good agreement of the near‐field jet decay. None of the eddy‐viscosity models was capable of predicting the profiles of the jet turbulence intensities. The RSMs, especially the standard RSM, were able to produce much better predictions of the features of the jet in comparison with the eddy‐viscosity models. The standard RSM predictions were found to agree reasonably well with the experimental data.

Research limitations/implications

The conclusion, that among the tested RANS turbulence closure models, the RSM appeared the only one capable of reproducing reasonably well the experimental data concerns only the jet flow case examined here. Also, the average computational time for a single run was quite long, i.e. 340 h, but it is believed that parallel computing will reduce it considerably.

Originality/value

The numerical results reported in this paper provide a comparison between several RANS turbulence closure models for simulating a turbulent free jet issuing from an equilateral triangular nozzle.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 19 no. 7
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 13 February 2017

Sherazed Hamza-Reguig, Nabila Boukhari Benahmed Daidj, Sabrine Louala, Ahmed Boualga and Myriem Lamri-Senhadji

The purpose of this study was to investigate the impact of replacing two different fats on dyslipidemia, glycemic balance and adipose tissue redox status in obese rats.

Abstract

Purpose

The purpose of this study was to investigate the impact of replacing two different fats on dyslipidemia, glycemic balance and adipose tissue redox status in obese rats.

Design/methodology/approach

Obesity was induced by feeding a high-mutton-fat diet during three months. An experimental group (n = 24) was divided into two groups that were fed during one month, 20 per cent of margarine or sardine oil. At Day 30, six rats from each group were sacrificed and the remaining rats were then subjected to a change in diet for one month: margarine was replaced by sardine oil and inversely, and then the rats were sacrificed. Three other groups (n = 6), each fed during two months, 20 per cent of margarine, sardine oil or mutton fat, served as controls.

Findings

Substitution of sardine oil by margarine compared to control sardine oil had increased triacylglycerols (TGs), glycosylated hemoglobin (HbA1c) and isoprostanes (IsoPs) values, but decreased thiobarbituric acid reactive substances (TBARS) and superoxide dismutase activity. Replacing margarine by sardine oil compared to control margarine reduced total cholesterol, TG, HbA1c, TBARS and IsoP contents but enhanced glutathione reductase and peroxidase activities. Nevertheless, comparing with the mutton fat, the two substitutions had improved glycemic and lipidic abnormalities and attenuated lipoperoxidation by enhancing enzymatic antioxidant defense. These favorable effects were better when margarine was replaced by sardine oil.

Originality/value

Substituting margarine with sardine oil seems to attenuate beneficial cardiometabolic risk markers associated to obesity and potentiate efficiency adipose tissue against the oxidative stress induced by the obesogenic diet.

Details

Nutrition & Food Science, vol. 47 no. 1
Type: Research Article
ISSN: 0034-6659

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Article
Publication date: 28 October 2014

Mohamed Hichem Gazzah and Hafedh Belmabrouk

The effects of a co-flow and inlet jet temperature on local entropy generation in turbulent round jets have been studied numerically. The second-order closure turbulence…

Abstract

Purpose

The effects of a co-flow and inlet jet temperature on local entropy generation in turbulent round jets have been studied numerically. The second-order closure turbulence model has been used. The paper aims to discuss these issues.

Design/methodology/approach

Numerical results are presented and discussed.

Findings

The numerical results for the mean quantities, entrainment of air, mixing efficiency, generation of entropy rate and Merit number are presented and discussed.

Originality/value

The expansion of the jet at low velocity of the co-flow and high inlet jet temperature enhances the heat transfer rate and reduces the irreversibility of the jet.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 24 no. 8
Type: Research Article
ISSN: 0961-5539

Keywords

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