Génie mécanique

Nombre total de résultats : 207
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A numerical study of viscous dissipation effect on non-Newtonian fluid flow inside elliptical duct

Haroun RAGUEB, Kacem MANSOURI  (2013)

Laminar heat transfer inside duct with elliptical cross section, subjected to uniform wall temperature is studied by taking into account the viscous dissipation. The temperatures distributions are evaluated numerically by using a dynamic Alternating Direction Implicit method (dADI). Nusselt number (Nu) is presented graphically for various Brinkman number (Br) and aspect ratio for a non-Newtonian fluid described by the power law model. The results obtained showed a good agreement with those found in the literature for fluid flow in circular cross section ducts and in elliptical cross section without viscous dissipation effects. It is shown that in the fully developed region and for Br ≠ 0, Nusselt number has a fixed asymptotic value independent of Brinkman number (Br). In the thermally developing region, it is observed a single fixed point independent of heating or cooling condition which the numerical value is equal to the asymptotic Nusselt number. Another relevant feature is that in the fully developed region, the Nusselt number increases with the aspect ratio. Voir les détails

Mots clés : Elliptical duct section, Viscous dissipation, Non-Newtonian fluids, Power law model, Laminar forced convection

Numerical study of thermal Effects in the hydrodynamic Behavior of textured journal bearings

N. Tala-ighil, M. Fillon, A. Brick Chaouche, A. Mokhtari  (2015)

The journals bearing characteristics with texture presence on the bearing surface are investigated. The thermaleffect has been studied. The used numerical approach in this analysis is Finite Difference Method. The textured bearingperformance enhancement passes essentially by a minimum film thickness and a friction torque improvement through anappropriate surface texture geometry and right texture distribution on the bearing surface. It is found that the simulationresults are in good concordance with those issued from the litterature. The obtained results by considering thetemperature effect are more realistic. Voir les détails

Mots clés : Hydrodynamic lubrication, journal bearing, texturation, dimple

Surface texturing effect comparative analysis in the hydrodynamic journal bearings

Nacer TALA IGHIL, Michel FILLON  (2015)

The journal bearing is a complex system with high film convergence and with cavitation hydrodynamicphenomena. The surface texturation influence study on journal bearing performances requiresunavoidably experimental investigations followed by a numerical modelling of the problem. This work consistsin modellization and understanding of the journal bearing characteristics in both cases of presence orabsence of textures onto the bearing surface. The finite difference method is used as numerical approachin the analysis. The textured bearing performance enhancement passes essentially by an improvement of aminimum film thickness, a maximum pressure and a friction torque through an appropriate surface texturegeometry and appropriate texture distribution on the contact surface. It is found that the simulationsresults are in good concordance with litteratures. The texture area position on the bearing surface is theprimary endpoint for journal bearing performance enhancement. The best design of textured area dependsstrongly on the geometrical parameters and the journal bearing operating conditions. Voir les détails

Mots clés : Journal bearings, Reynolds equation, Hydrodynamic lubrication, Stribeck curve, texture

Effect of textured area on the performances of a hydrodynamic journal bearing

Nacer Tala-Ighil, Michel FILLON, Patrick Maspeyrot  (2011)

A growing interest is given to the textured hydrodynamic lubricated contacts. The use of textured surfaceswith different shapes of microcavities (textures) and at different locations of the texture zone can be aneffective approach to improve the performance of bearings. The present study examines the texturelocation influence on the hydrodynamic journal bearing performance. A numerical modelling is used toanalyze the cylindrical texture shape effect on the characteristics of a hydrodynamic journal bearing. Thetheoretical results show that the most important characteristics can be improved through an appropriatearrangement of the textured area on the contact surface. Voir les détails

Mots clés : textures, Hydrodynamic lubrication, journal bearing, Finite difference method

Effects of surface texture on journal-bearing characteristics understeady-state operating conditions

N. Tala-ighil, P. Maspeyrot, M. Fillon, A. Bounif  (2007)

Developments in microscopy have a profound effect on the resurgence of tribological applications at themicroscopic level. Using surfaces with controlled micro geometry may prove an effective approach toimproving bearing performance. It is consequently of interest to study the lubrication of journal bearingsystems taking into consideration the effect of surface geometry design. A numerical approach is used inthe analysis of texture effects on bearing characteristics. The results from investigating the performanceof bearing surfaces with spherical dimple textures suggest that contact characteristics such as minimumfilm thickness, maximum pressure, axial oil film flow, and friction torque may be improved through anappropriate surface texture geometry and appropriate textures distribution on the contact surface. Themain purpose of our work is to model and understand the evolution of journal-bearing characteristics withtextures. A rigorous methodology is recommended. The work is divided into two steps. The first oneserves to quantify the evolution of the characteristics with the texture parameters and to deduce theiroptimized values. The second step enhance the performance of the journal bearing by progressivelytaking into account the optimized values of texture parameters, especially the textures disposition. Voir les détails

Mots clés : textured surface, dimples, Hydrodynamic lubrication, journal bearing, Finite difference method

Damage modelling in thermoplastic composites reinforced with natural fibres under compressive loading

Ahcene MOKHTARI, Mohand Ould Ouali, Nacer Tala-Ighil  (2015)

In this work, the compression failure of thermoplastic composites made of jute/polypropylene is investigatedby experimental and numerical studies. Two laminate specimen’s lengths with different fibre orientations have been considered to analyse this composite type response to a compressive solicitation. The applied numerical model permits to understand the mechanisms of damage and evolution in the laminate.The interlayer damage (delamination) and the intra-layer damage (matrix cracking) have been modelled bythe combined use of the Cohesive Zones model (CZM) and the Matzenmiller, Lubliner and Taylor (MLT)mechanical model. It was found that the loading conditions of laminates and the fibres orientation affect the compression failure load of the thermoplastic composites. Voir les détails

Mots clés : Jute/polypropylene, mechanical behaviour, damage, laminates, modelling

Etude expérimentale et analyse probabiliste du comportement à la rupture en traction de composites verre-perlon-acrylique à usage orthopédique

Sihem ACHOURI, Bachir Redjel  (2014)

Les effets de la nature des séquences de la stratification ainsi que les influences significatives du sens de découpe des échantillons par rapport au sens du flux de moulage sur le comportement mécanique en traction d’une série de matériaux composites stratifiés sont mises en évidence à partir d’une analyse de leurs propriétés mécaniques. Ces stratifiés à usage orthopédique et à base de résine acrylique renforcée de couches de fibres de verre et de perlon sont disposées selon trois différentes architectures. Une importante dispersion est observée sur les résultats de mesure du module de Young et des contraintes à la rupture. Ces dernières montrent des valeurs supérieures dans le sens perpendiculaire à celui du flux de moulage. La mesure de la fragilité, la caractérisation du comportement à la rupture de ces stratifiés ainsi que l’aspect probabiliste de cette dernière sont décrits quantitativement à partir de l’application du modèle probabiliste à deux paramètres de Weibull. Le caractère fragile de la rupture de ces stratifiés est ainsi traduit par les faibles valeurs mesurées des modules de Weibull. Un constat des principaux mécanismes responsables de la rupture est dressé à partir des observations microscopiques des faciès de rupture des éprouvettes rompues. Voir les détails

Mots clés : stratification, Fibre De Verre,  Perlon,  Dispersion,  Module De Weibull

New Approach to Modeling a planar flexible continuum robot simulating elephant trunk

MAHFOUDI Chawki, AMOURI Ammar, ZAATRI Abdelouahab  (2013)

Research on the modeling of continuum robots is focused on ways to construct the geometric models, while maintaining maximum specificities and mechanical properties of the robot. This paper presents a new approach of geometric modeling of continuum planar multi- sections robots, assuming that each section is curved in a circular arc, while having inextensible central axis of the structure. The direct geometric model is calculated analytically, whereas the extreme points (used in calculating the inverse geometric model) of each section are calculated numerically using a particle swarm optimization (PSO) method. One advantage of this method is to simplify the mathematical calculations and transform the complex problem into a simple numerical function; which allows the knowledge of the form of the central axis of the robot. Simulation examples using this method are carried to validate the proposed approach. Voir les détails

Mots clés : Flexible Continuum Robot, central axis, PSO, Khalil Klifinger method

A numerical investigation of both thermal and texturing surface effects on the journal bearings static characteristics

Nacer Tala-Ighil, Michel FILLON  (2015)

Journal bearing characteristics modellization has been investigated in this paper for both cases of texture presence or absence onto the bearing surface. The thermal effect has been studied. The used numerical approach in this analysis is finite difference method. The textured bearing performance enhancement passes essentially by a minimum film thickness and a friction torque improvement through an appropriate surface texture geometry and right texture distribution on the bearing surface. It is found that the simulations results are in good concordance with those issued from the literature. The obtained results by considering the temperature effect are more realistic. Voir les détails

Mots clés : Journal bearings, Reynolds equation, Hydrodynamic lubrication, Stribeck curve, texture


BOULKROUNE Sofiane, Kholai Omar, Boudebous Saadoune  (2012)

This work consists to a parametric study of heat transfer in laminar mixed convection inside a square cavity. Our objective is the determination of a parameter that able to locate the transition between the forced, mixed and natural convection for a low Prandtl number fluid (Pr = 0.015). The proposed geometry is a cavity with moving left vertical wall which is maintained to cold temperature and with the right fixed wall at hot temperature. The horizontal walls are adiabatic. The governing equations of this problem are: the equation of conservation of mass, the Navier Stokes equations and energy conservation equation. These differential equations are discretized by the finite volume method on a staggered grid and the SIMPLE algorithm was used for the iterative procedure.The numerical simulations were made for a wide range of Reynolds numbers (1 ≤ Re ≤ 600), and Grashof (29.2 ≤ Gr ≤ 685800). The frontiers of transition from one regime to another regime of convection (forced-mixed and mixed-natural) were determined by a modified Richardson Number. Finally, we found that the parameter which specifies the natural convection regime is Gr/Re1, 58194 and for the forced convection regime is Gr/Re1, 50235. Voir les détails

Mots clés : square cavity, low Prandtl number, modified Richardson Number