In water supply installations, noise pollution often occurs. As a basic component of a system, a flush valve may frequently be a source of noise and vibration generated by cavitation or high turbulence levels. During valve closing or valve opening, cavitation can be a problem. In order to decrease the noise and to improve the design inside a flush valve, some experimental and numerical analyses were carried out in our laboratories. These analyses led to some improvements in the design of the valves. Cavitation occurrence was more specifically addressed, using numerical simulation, and this is the main aim of the present paper. Particularly, the use of a simplified numerical test without cavitation model is compared with one using a cavitation model. In order to define potential cavitation risks in some parts of the valve, it has been found that a simplified approach provides an accurate overview. Computational Fluid Dynamics (CFD) simulations of cavitating flow of water through an industrial flush valve were performed using the Reynolds averaged Navier-Stokes (RANS) equations with a near-wall turbulence model. The flow was assumed turbulent, incompressible and steady. Two commercial CFD codes (Fluent 6.3 and Star CCM+ 3.04.009) were used to analyse the effects of inlet pressure as well as mesh size and mesh type on cavitation intensity in the flush valve.

In mass production, the customer defines the constraints of assembled products byfunctional and quality requirements. The functional requirements are expressed by thedesigner through the chosen dimensions, which are linked by linear equations in the caseof a simple stack-up or non-linear equations in a more complex case. The customer qualityrequirements are defined by the maximum allowable number of out-of-tolerance assemblies.The aim of this paper is to prove that quality requirements can be accurately predicted inthe design stage thanks to a better knowledge of the statistical characteristics of theprocess. The authors propose an approach named Advanced Probability based ToleranceAnalysis (APTA), assessing the defect probability (called PD)that the assembled product has of not conforming to the functional requirements. Thisprobability depends on the requirements (nominal value, tolerance, capability levels) setby the designer for each part of the product and on the knowledge of production devicesthat will produce batches with variable statistical characteristics (mean value, standarddeviation). The interest of the proposed methodology is shown for linear and non-linearequations related to industrial products manufactured by the RADIALL SA Company.

Cette étude expérimentale présente l’étude du comportement mécanique d’un polyamide 66(PA66) renforcé par des fibres de verre courtes fréquemment utilisées dans l’industrieautomobile. Afin d’étudier l’influence de la teneur en humidité, de la quantité de fibresde verre introduite dans la matrice et de la vitesse de déplacement, une série d’essais detraction a été réalisée sur du polyamide renforcé ou non avec des fibres de verre courtesà différents fractions volumiques : 10, 20 et 30 wt%. Les résultats montrent la dépendancedu matériau aux différents paramètres cités précédemment. La technique de thermographieinfrarouge (IR) a été utilisée pour déterminer l’évolution de la température à la surfacedes matériaux au cours des essais de traction. Un processus de localisation de ladissipation thermique a pu être identifié à partir des images thermiques.

An analytical solution to compute the 3D steady state temperature distribution in abearing ring is presented in this paper. The ring is formed by a hollow cylinder of finitelength. Its radial external surface is subjected to localized, identical heat sources,equally spaced in the azimuth direction. This surface is also subjected to convectivecooling while as the internal surface is maintained at a uniform temperature. Thedeveloped solution is explicit and does not impose any restriction on the geometrical orphysical parameters.

La méthodologie proposée pour l’étude du comportement de matériaux cellulaires soussollicitation dynamique est abordée par une approche multi-échelles. Le comportement desmousses polymères étudiées dépend du matériau constitutif, et de sa structure poreuse. Lesmatériaux cellulaires de l’étude sont constitués de grains millimétriques poreux; le cœurde ces grains est constitué de cellules microscopiques. La méthodologie proposée vise àreproduire la morphologie multi-échelles du matériau cellulaire, celles des grains et descellules, d’implémenter des modèles de comportement simples à ces différentes échellesafin de reproduire les phénomènes physiques complexes observés et la réponse macroscopiquedu matériau. L’observation et l’analyse des phénomènes locaux est un travail préparatoireà la modélisation multi-échelles. Cet article décrit les méthodes expérimentales etnumériques qui ont été développées pour l’observation fine de la structure des matériauxcellulaires, et quantifier des déformations et des dommages de ces structures à l’échelledes cellules et des grains. Deux approches de modélisation ont été ensuite envisagées; unmodèle éléments-finis pour décrire la structure des grains, et une autre approchenumérique plus originale qui s’appuie sur la méthode des éléments discrets pourreprésenter la structure microscopique des cellules.

L’assemblage des rails de chemin de fer se fait généralement à travers un procédé desoudage par aluminothermie. Ce procédé consiste en la coulée de métal de jonction entreles deux extrémités de rails à assembler. La qualité de cet assemblage dépend étroitementdes conditions de la réalisation qui sont généralement difficiles à respecter. En effet,les techniques classiques de contrôle des rails, mettent souvent, en évidence la présencedes défauts de soudure dans la jonction. Selon les observations, ces défauts peuvent êtreclassés en deux types : défauts d’adhésion (ou défauts de collage) et défauts de porosité(ou défauts de soufflures multiples). Chacun de ces défauts, peut constituer un siteprivilégié de concentration des contraintes. Selon le niveau de ces contraintes, deséventuels processus d’endommagement risquent de se développer et mettant le rail horsservice. Il semble donc nécessaire de modéliser le comportement mécanique de ces souduresavec ces défauts en vue de les classer par leur criticité. Dans cette étude, nous avonsdonc modélisé avec un même chargement et avec les mêmes conditions aux limites, lajonction de soudure pour chaque type de défaut. Les résultats obtenus sont très concluantset permettent de bien orienter l’approfondissement de notre analyse coté paramètres desoudage.

This paper presents thermohydrodynamic solutions for a finite-width journal bearing withsingle axial groove on the crown by considering turbulent effects in lubricant film.Appropriate governing equations and boundary conditions are used for the fluid flow andheat transfer process occurring in finite full journal bearings. A general computerprogram is developed to numerically solve the set of governing equations. Results areprovided for THD characteristics of journal bearing in terms of Reynolds number, clearanceratio and eccentricity ratio. Good agreement with published experimental results wasachieved. The results indicate that the bearing temperature field and pressure field areconsiderably influenced by the journal bearing parameters.

This paper investigates the flow boiling heat transfer in microchannels with the aim ofdeveloping compact cooling systems which can be adapted to miniaturized power components.Nano- and micro-surface treatments were used as innovative techniques to improve the heattransfer performance as well as to delay the intermittent dryout. It was observed that themicro-structured surfaces show significant enhancements (up to 85%) in heat transfercompared to the smooth surfaces. Especially, using the highly-wetted structured surface,the intermittent dryout is improved.

The paper concerns the transient thermal behavior of a conrod bearing in an automotive engine subjected to various running conditions. The thermal model is oil shear and contact friction heat generation components. The first part of the paper covers some of the industrial and scientific aspects related to bearings seizure, and emphasizes the importance of removing this failure mechanism as early as the incipient development stages of new automotive engines. The second part concerns several of the broad array of factors that approximate a seizure mechanism. In the third and final part, the mathematical model for conrod bearings seizure is revealed. The objective of the paper is to confirm the conrod seizure model’s utility, complementary with more refined approaches such as the thermo-elasto-hydrodynamic approach.

The present paper is concerned with the thermoelectric behaviour of CFRP compositesamples subjected to DC currents in view of developing experimental and modelling toolsfor the characterisation of the thermo-electro-mechanical behaviour of composite materialsfor aircraft applications. DC currents up to 8 A are injected through the specimens endsides by employing several different electrode techniques whose performances are assessedand compared. Sample and electrode contact resistances are measured for different valuesof the injected current. The transient and permanent temperatures fields promoted by theinjected currents are experimentally measured by infrared thermography. The temperaturefields are simulated numerically by a thermoelectric coupled model employing theABAQUS®FE commercial code; temperatures can be also approximately calculated by a simple lumpedparameter model discarding thermal conduction. The comparison between simulations by themodels and measurements allows employing the simplified model as a tool to designthermo-electro-mechanical tests.

This paper explores analytically the nonlinear dynamic behavior of rotors. Coupled nonlinear equations of motion are formulated using Hamilton’s principle. The rotor model is composed of a rigid disk and a flexible shaft which is characterized as a beam of circular cross section. Various influences are taken into account like the effect of higher order large deformations, rotary inertia, gyroscopic effect, rotor unbalance and the effect of a dynamic axial force. Forced response due to a mass unbalance is presented first for the linear analysis and then perturbation techniques are used to solve the complete equations of motion including nonlinear terms. Method of multiple scales is applied to examine the nonlinear behaviour of the rotor system. Resonant curves are plotted for different possible resonance conditions. It is concluded that the higher order large deformations and axial force acting dynamically on the rotor have a significant effect on its nonlinear response. This response varies for different parameters of the rotor like an unbalance mass and diameter of the shaft.

Silicon carbide particulate reinforced aluminum (Al/SiCp) Metal Matrix Composites (MMC) is finding increased applications in Industries due to its unique advantages. Holes are to be drilled in many applications for joining and assembly purposes. Friction drilling is a newer non-traditional hole-making chip less process used to make holes in a single step. The manuscript first discusses the mechanical properties such as tensile strength and micro hardness of Al/SiCp-MMC composites, then it discusses the roundness (hole diameter accuracy) errors on dry friction drilled holes. The parameters considered for the experiments are: the composition of work piece, work piece thickness, spindle speed, and feed rate. The results indicated that the increase in the composition of wt% of SiCp particles increases the tensile strength, hardness. The drilling test results indicated that moderate wt% of SiCp gives better results. Higher spindle speeds and higher feed rates increase the roundness error. The highly influential parameter which affects the roundness error is feed rate. Increase in plate thickness also increases the roundness error in drilling of MMC composites.

Several studies have been carried out in order to describe the impact ofwater-contaminated lubricants on lubrication performance. One approach considers thewater-contaminated oil as a homogeneous lubricant with physical characteristics varyingwith water concentration. The presented work is being achieved in order to experimentallyvalidate this theory. First investigations showed that the variation of contaminatedlubricant viscosity has the most significant effect on lubricating performance.Consequently, the lubricant viscosity is the only parameter taken into account in thisstudy. Thus, based on the rheological measurements, water-in-oil emulsion viscosity hasbeen modelled according to water concentration and temperature. Water concentration wasconsidered relatively to total mass of oil: the mass concentration varied then from 0 to7% and temperature from 10 to 80 °C. Viscosity modelling was then used to perform thenumerical simulations of a hydrodynamic thrust bearing supplied with water contaminatedoil. Finally, the experimental validation will be done by measuring various bearingcharacteristics like the film/pad temperature, the film thickness and the friction torqueon a tilting pad thrust bearing test rig.

Cette étude présente une machine frigorifique fonctionnant suivant un cycle à compression-absorption. Le système proposé utilise le couple ammoniac-eau comme fluide frigorigène et opère à trois niveaux de pression. L’absorbeur fonctionne à une pression intermédiaire Pint, prise entre la pression de l’évaporateur (PEV) et celle du condenseur (PCD). Les principaux éléments du système proposé sont modélisés. Les résultats de la simulation numérique sont comparés à ceux relatifs au système conventionnel. L’étude comparative met en évidence les avantages du système objet de cette étude. Elle prouve le double avantage de la pression intermédiaire non seulement dans l’amélioration des performances de la machine à absorption mais aussi dans la réduction de la température du fonctionnement du générateur. Nous avons montré que pour des températures d’évaporation et de condensation prises respectivement à –10 °C et 40 °C, le cycle frigorifique fonctionne à une température du générateur TGE = 75 °C avec un COP de l’ordre de 0,56. La présente étude révèle que pour les mêmes conditions de fonctionnement, la machine frigorifique simple étage, présente un COP qui ne dépasse pas 0,51 avec une température du générateur de l’ordre de 135 °C. Le système hybride présente ainsi le privilège de fonctionner à basse température et de présenter des performances relativement améliorées.

There has been a number of initiatives launched in the field of lubrication as potentialsources of improvements in energy efficiency in a wide range of engineering products,plant and processes. Attention is being focussed on bearings to improve both performanceand efficiency in fields such as automotive, machine tools, industrial and powergeneration plant. This paper reviews some of the background to these drives andillustrates how a novel design of adjustable fluid film hydrodynamic journal type bearingshows promise to both improve performance and save energy. Theoretical modelling andpractical tests have demonstrated clear improvements over conventional fluid filmbearings, along with a number of other characteristics offering benefits that may be ofinterest to designers and users of such bearings.

This work gives an overview of the theoretical and experimental achievements of mechatronics applied to fluid film bearings. Compressible and uncompressible fluids are addressed. Rigid and elastic (deformable) bearing profiles are investigated. Hydraulic, pneumatic, magnetic and piezoelectric actuators are used. The ideas of combining control techniques, informatics with hydrodynamic, thermo-hydrodynamic, elasto-hydrodynamic and thermo-elasto-hydrodynamic lubrication techniques are carefully explored in this paper, considering theoretical as well as experimental aspects. The main goal of using controllable fluid film bearings is to improve the overall machine performance by: controlling the lateral vibration of rigid and flexible rotating shafts; modifying bearing dynamic characteristics, such as stiffness and damping properties; increasing the rotational speed ranges by enhancing damping and eliminating instability problems, for example, by compensating cross-coupling destabilizing effects; reducing start-up torque and energy dissipation in bearings; compensating thermal effects. It is shown that such controllable fluid film bearings can act as “smart” machine components and be applied to rotating and reciprocating machines with the goal of avoiding unexpected stops of plants, performing rotor dynamic tests and identifying model parameters “on site”. Emphasis is given to the controllable lubrication (hybrid and active) applied to different types of oil film bearings under different lubrication regimes, i.e., as tilting-pad journal bearings, multi-recess journal bearings and plain journal bearings. After a comprehensive overview of the theoretical and experimental technological advancements achieved in university laboratories, the feasibility of industrial applications is highlighted, trying to foresee the future trends of such mechatronic devices.

Heat release rate fluctuations are the source of combustion instabilities that causerecurrent problems in many combustors. These quantities are difficult to measure andoptical techniques are generally implemented. The initial validation of an alternativemethod is presented in the case of pulsated laminar premixed flames. The technique relieson determining the travel time of ultrasonic waves propagating through the flow. The linkbetween heat release rate fluctuations and perturbations in the travel time of ultrasonicwaves is established. Measurements made with this method are compared with opticalmeasurements and an analytical model. A good agreement is obtained for the gain and phaseof the transfer function between perturbations in the sound travel time and heat releaserate disturbances when the flame is submitted to harmonic modulations of the flow. Thiswork validates the principle of the proposed technique and lays the foundations for futuredevelopments.

The focus of this comparative-numerical study is to investigate the effects of advancedcooling hole geometries on film cooling effectiveness. Computational results are presentedfor a row of coolant injection holes on each side of an asymmetrical turbine blade modelnear the leading edge. Six film cooling configurations are considered in the presentstudy, namely: (1) a cylindrical film hole, (2) a shaped film hole, (3) a uniform filmslot, (4) a convergent film slot, (5) a crescent film hole, and (6) a trenched film hole.All simulations are conducted for the same density ratio of 1.0 and the same inlet plenumpressure. A new parameter, Rc, is defined to measure the rate of bladecoverage by the film cooling. Results show that, at the suction side, except for thetrenched case, all configurations provide an increase of film effectiveness, specially thecrescent slot case which provides the highest increase over the baseline case. On pressureside, the five configurations produce better quality of cooling and an enhancement whichreaches 60% for the crescent hole case. The best blade coverage by the film cooling isallotted to the two cases: uniform and converge slot configurations.

Nous étudions expérimentalement et numériquement la dynamique de bulles d’air isoléestraversant l’interface initialement plane entre deux liquides newtoniens. Les liquidesutilisés dans les expériences nous permettent d’obtenir des rapports de viscosité quipeuvent varier de deux ordres de grandeur entre les deux couches et dans une moindremesure, de faire varier le contraste de densité et la tension interfaciale rencontrés parla bulle lors de la traversée de l’interface. Deux dispositifs d’injection différents sontutilisés afin d’obtenir des bulles dont les diamètres s’échelonnent typiquement entre 1 mmet 2 cm et dont les plus grosses adoptent une forme torique. Nous réalisons en parallèledes simulations numériques axisymétriques à l’aide de deux approches distinctes baséespour l’une sur un modèle de capture d’interface (de type VOF mais sans reconstructiond’interface), pour l’autre sur un modèle de Cahn-Hilliard couplé aux équations deNavier-Stokes.