Browsing by Author "Merah, Abdelkrim"

Now showing 1 - 15 of 15

3D Numerical study of magnetohydrodynamic instability in liquid metal taylor-couette flow
(2015) Merah, Abdelkrim; Mokhtari, Faiza; Bouabdallah, A.; Adnane, M.
This purpose is about a 3D study of magnetohydrodynamic (MHD) instability in liquid matal Taylor-Couette flow, this problem is receiving more and more research interest due to its application in the engineering, oceanography and the astrophysical research The Taylor-Couette system consists of two coaxial cylinders in differential rotation, which is considered as a hydrodynamic model system, allowed researchers to progress in understanding the laminar-turbulent transition phenomena. A set of states found in narrow gap of Taylor-Couette systems where the outer cylinder is held fixed and the inner cylinder speed increased. The symmetry breaking parameter is the Taylor number Ta that gives a measure of the ratio of centrifugal forces to viscous forces. When the liquid is replaced by an electrically conducting fluid and an external magnetic field is applied, this leads to MHD Taylor-Couette flow. Additional body force, Lorentz force, acting on the fluid arises. Lorentz force is in the direction perpendicular to both magnetic and electric fields. The behaviour of flow depends on strength and geometry of applied field, magnetic and electric properties of the liquid, cylinders and endplates. In this work, the MHD instability Taylor-Couette flow is considered for liquid sodium with its magnetic Prandtl number Pm <1. The results of pressure and angular momentum in the Taylor-Couette flow under the effect of an external uniform axial magnetic field B=4 Tesla are investigated numerically for the different cases of electrically conducting or insulating walls at the Ekman cell, at the middle of the first Taylor-votex flow (TVF) and between two cells.
Analysis of the Reliability and Availability of the Algiers Metro Traction System Based on the Pareto and Weibull Three Parameters Methods
(Springer, 2025) Siguerdjidjene, Hakim; Merah, Abdelkrim; Saidi, Djamel; Houari, Amin
Rail transport by metro is a socio-economic form of transport, and the reliability of traction systems is considered to be one of the key factors required to ensure its smooth operation, safety and public comfort. In addition, it provides rapid mobility for citizens between different areas of a city and reduces the road congestion in urban areas by offering a fast, efficient transport alternative. This research is based on an in-depth analysis of the most frequent operating time data, failures and breakdowns (mechanical, electrical, etc.) of the ELDJAZAIR-Alger metro company's traction systems, with the aim of analysing the reliability and availability of these two series of traction systems, in order to minimize interruptions and maintain a high level of service to meet users' needs. Historical data was collected and thoroughly analyzed. Firstly, we visualized this data in the form of a Pareto chart known as the ‘20/80% rule’ (A, B, C) (Thomas E. Nisonger in The “80/20 Rule” and Core Journals. The Serials Librarian 55(1):62–84, in order to determine the highest priority areas. This makes it easier to process the data. Second, the reliability of vehicle traction systems is analyzed using the three-parameter Weibull probability criterion R (t, γ, η, β) (Vonta Ilia, Mangey Ram. Reliability Engineering: Theory and Applications. Publisher: CRC Press-Taylor & Francis Group ISBN: 9,780,815,355,175. (2018)), based on the calculation of the time-to-function and mean time between failures and the failure rate λ (t). The results obtained using the Pareto method show that the most critical faults are classified in zone A: where 20% corresponds to 80% of the total number of faults, representing five faults designated by codes as follows: [CLS, MON, CAJ, CAU, VAUX], which are more critical and take priority over emergency intervention by the maintenance department. The results of the analysis show that the correlatio n coefficient equals to 0.976, which indicates a very strong positive linear relationship between the percentage of variable failures and time and the reliability R (t, γ, η, β) of traction systems is almost in the approximate 50% with its parameters: γ = 0, β = 3.9776, η = 1067.62h and availability A(t) decreases over time, which requires measures to improve the latter by including new techniques for service management, control, preventive and corrective maintenance
Application de la méthode " level-set " à la reconstruction géométrique de contours
(2006) Merah, Abdelkrim
Le travail effectué dans le cadre de ce mémoire se rapporte à la mise en oeuvre d’une méthode variationnelle à base de modèles déformables géométriques à savoir la méthode « level set ». La méthode level-set est très indiquée pour le suivi et la capture d’interfaces mais elle nécessite néanmoins une réinitialisation. La reconstruction géométrique de contours intéresse de nombreux domaines à l’exemple de l’imagerie médicale, la télédétection, le suivi de trajectoires, le maillage et la reconstruction d’objets, etc. L’objectif principal de ce travail est d’élaborer et mettre en oeuvre, dans un premier temps, un programme permettant la reconstruction et l’évolution des contours géométriques d’une manière globale puis d’entrevoir un élargissement à la segmentation d’images où les contours sont difficiles à identifier. La mise en oeuvre informatique du programme élaboré sous MATLAB sur la base de la méthode Level-Set permettant l’évolution de contours suivant la direction normale avec une vitesse constante, a aboutit à des résultats intéressants. L’initialisation est faite par un cercle positionné à l’intérieur du domaine de définition. La discussion et l’interprétation de ces résultats montrent l’intérêt multidisciplinaire des « levelset » et met en évidence les possibilités de la méthode dans le domaine de la segmentation d’images et de la reconstruction des contours géométriques (2D)
Entropy generation optimization of a hemispherical anchor agitated batch reactor
(American Institute of Physics, 2019) Baghli, Houda; Tchouar, Noureddine; Merah, Abdelkrim
The entropy generation optimization of a hemispherical anchor agitated batch reactor has been studied, to optimize the heat transfer in the process of production of a cosmetic cream cooled by a jacket at industrial scale. The main objective of this optimization of the cooling condition was the improvement of the product quality and the reduction the energy consumption of the process. The phenomenon considered is two-dimensional, axisymmetric and permanent. The entropy generation optimization has been carried out successfully by the simulation of the heat transfer throw the reactor wall and the agitated fluid. The results give the optimum speed velocity for agitation and the optimal cooling time and coolant temperature
Experimental investigation into the tensile strength post-repair on damaged Aluminium 2024 -T3 plate using hybrid bonding/riveting
(2024) Merah, Abdelkrim; Houari, Amine; Madani, Kouider; Belhouari, Mohamed; Amroune, Salah; Chellil, Ahmed; Yahi, Cherif Zineelabidine; R.D.S.G., Campilho
Since the implementation of repair processes by composite patch bonding, this process has consistently demonstrated high performance across various industrial sectors, especially in the fields of aeronautics, aerospace and civil engineering. Consequently, there are situations in which the riveting process becomes the sole solution, particularly when the structure is subjected to severe mechanical or thermo-mechanical stresses, since adhesives have low mechanical strength after aging. Each method has its own set of advantages and disadvantages. The current trend is to combine these two processes to minimize their drawbacks as much as possible. The objective of this work is to present an experimental study into the repair of an aluminum plate AL2024-T3 with a central circular notch using a patch of different nature (metal or composite), under tensile loading conditions. The repair composite considered is a carbon/epoxide. The results of the tensile tests clearly showed that the repair by the combination of the two processes clearly improves the mechanical strength of the damaged structure. A comparison of the results of the experimental curves obtained on riveted, bonded, and hybrid assemblies has been taken into consideration.
Experimental Investigation Into the Tensile Strength Post-Repair on Damaged Aluminium 2024 -T3 Plates Using Hybrid Bonding/Riveting
(Sciendo, 2024) Merah, Abdelkrim; Houari, Amin; Madani, Kouider; Belhouari, Mohamed; Amroune, Salah; Chellil, Ahmed; Yahia, Cherif Zineelabidine; Campilho, Raul D.S.G. Duarte Salgueiral Gomes
Since the implementation of repair processes by composite patch bonding, this process has consistently demonstrated high performance across various industrial sectors, especially in the fields of aeronautics, aerospace and civil engineering. Consequently, there are situations in which the riveting process becomes the sole solution, particularly when the structure is subjected to severe mechanical or thermo-mechanical stresses, since adhesives have low mechanical strength after aging. Each method has its own set of advantages and disadvantages. The current trend is to combine these two processes to minimise their drawbacks as much as possible. The objective of this work is to present an experimental study on the repair of an aluminium plate AL2024-T3 with a central circular notch using a patch of different nature (metal or composite), under tensile loading conditions. The repair composite considered is a carbon/epoxide. The results of the tensile tests showed that the repair by the combination of the two processes improves the mechanical strength of the damaged structure. A comparison of the results of the experimental curves obtained on riveted, bonded and hybrid assemblies has been taken into consideration.
Free surface study in silicon czochralski melt
(2014) Mokhtari, Faiza; Merah, Abdelkrim; Bouabdallah, Ahcene; Rouaiguia, Leila
Instabilities in silicon Czochralski crystal growth process in different geometries
(2010) Merah, Abdelkrim; Bouabdallah, Ahcene; Mokhtari, Faiza; Hanchi, S.; Alemany, A.
Numerical investigation of magnetic field effect on pressure in cylindrical and hemispherical silicon CZ crystal growth
(Wiley, 2012) Mokhtari, Faiza; Bouabdallah, Ahcene; Merah, Abdelkrim; Oualli, Hamid
A numerical investigation of the flow pattern between finite–length conical cylinders
(2017) Merah, Abdelkrim; Mokhtari, Faiza; Kelaiaia, Ridha; Hamrani, Abderrachid; Lalaoua, Adel
Numerical study of the effect of transverse magnetic field on cylindrical and hemispherical CZ crystal growth of silicon
(Thomson Scientific, 2010) Mokhtari, Faiza; Bouabdallah, Ahcene; Merah, Abdelkrim
Predicting damage in notched functionally graded materials plates through extended finite element method based on computational simulations
(Gruppo Italiano Frattura, 2024) Siguerdjidjene, Hakim; Houari, Amin; Madani, Kouider; Amroune, Salah; Mokhtari, Mohamed; Mohamad, Barhm; Ahmed, Chellil; Merah, Abdelkrim; Campilho, Raul D.S.G. Duarte Salgueiral Gomes
Presently, Functionally Graded Materials (FGMs) are extensively utilised in several industrial sectors, and the modelling of their mechanical behaviour is consistently advancing. Most studies investigate the impact of layers on the mechanical characteristics, resulting in a discontinuity in the material. In the present study, the extended Finite Element Method (XFEM) technique is used to analyse the damage in a Metal/Ceramic plate (FGM-Al/SiC) with a circular central notch. The plate is subjected to a uniaxial tensile force. The maximum stress criterion was employed for fracture initiation and the energy criterion for its propagation and evolution. The FGM (Al/SiC) structure is graded based on its thickness using a modified power law. The plastic characteristics of the structure were estimated using the Tamura-Tomota-Ozawa (TTO) model in a user-defined field variables (USDFLD) subroutine. Validation of the numerical model in the form of a stress-strain curve with the findings of the experimental tests was established following a mesh sensitivity investigation and demonstrated good convergence. The influence of the notch dimensions and gradation exponent on the structural response and damage development was also explored. Additionally, force-displacement curves were employed to display the data, highlighting the fracture propagation pattern within the FGM structure.
Résolution d'un problème de convection naturelle en 2D et 3D par la méthode spectrale
(AFM, Association Française de Mécanique, 2017) Bouarab, Samia; Mokhtari, Faiza; Kaddeche, Slim; Hamrani, Abderrachid; Merah, Abdelkrim; Haddad, Fadila
L'objectif de ce travail consiste à étudier le problème de la convection naturelle à l'intérieur d'une cavité carrée différemment chauffée à l'aide de la méthode spectrale. Les simulations numériques bidimensionnelles et tridimensionnelles sont effectuées pour différents nombres de Prandtl et de Rayleighcaractéristiquesde l'écoulement du fluide à l'intérieur de la cavité connu sous le nom d'écoulement de Hadley. La simulation numérique des écoulements incompressibles par les méthodes classiques tels que les différences finies, volumes finis et éléments finis, nécessite des temps de calcul relativement longs et une capacité de stockage très importante. Un modèle basé sur les méthodes spectrales a été développé et a mis en valeur la précision, la simplicité et la rapidité d'une telle méthode, notamment pour des simulations voulues de plus en plus proches de la réalité des processus multi-physiques complexes. La méthode spectrale sera utilisée dans notre étude afin d'effectuer des modélisations bidimensionnelles et tridimensionnelles des écoulements incompressibles en formulation vorticité-fonction de courant pour le modèle 2D et en utilisant la méthode d'Uzawa pour le modèle 3D. Les résultats de la simulation d'écoulements incompressibles par méthodes spectrales seront comparés à ceux obtenus par différences finies et en termes de temps de calcul et précision des résultats
Symmetry breaking in electromagnetic spherical Cz crystal growth with rotating crystal and crucible
(American Scientific Publishers, 2013) Mokhtari, Faiza; Bouabdallah, A.; Merah, Abdelkrim
Three-dimensional study of the pressure field and advantages of hemispherical crucible in silicon Czochralski crystal growth
(Wiley, 2010) Mokhtari, Faiza; Bouabdallah, Ahcene; Merah, Abdelkrim; Zizi, M.; Hanchi, S.; Alemany, A.