Publications Scientifiques
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Item Topological optimization of dimple distribution for enhanced performance in hydrodynamic porous self-lubricating journal bearings with sealed ends(Sage, 2025) Ifrah, Walid; Manser, Belkacem; Chellil, Ahmed; Ragueb, Haroun; Mechakra, Hamza; Khelladi, Sofiane; Belaidi, IdirThis study numerically investigates the impact of optimal textures location on the performance of hydrodynamic porous self-lubricating journal bearings with sealed ends, subjected to a stationary load. The analysis employs a modified Reynolds equation coupled with Darcy’s law to model fluid flow in both the lubricating film and the porous matrix, considering the hydrodynamic self-lubrication problem. The governing nonlinear PDE systems were solved numerically using the finite difference method, combined with Reynolds boundary conditions and continuity conditions for velocity and pressure at the film-bush interface. A Binary Genetic Algorithm (BGA) is employed to optimize the topological distribution of square dimples in the textured porous layer to enhance bearing performance. The study investigates the influence of key parameters, including applied load, rotational speed, permeability, and texture depth, on bearing characteristics such as minimum film thickness and friction coefficient. Results show good agreement with benchmark data and indicate a positive enhancement in porous bearing performance. In addition, findings demonstrate that increasing the permeability of the porous structure reduces bearing performance (up to 25% in minimum film thickness and 8% in friction coefficient). However, the application of the optimization technique identified an optimal arrangement of textures that compensates for these performance losses, even under severe working conditions. Texturing the outlet region of the contact (beyond 180°) at the cavitation zone causes a micro-step bearing mechanism, generating localized pressure recovery within the textured area, significantly enhancing the minimum film thickness (up to 12%), reducing friction (up to 23%), and minimizing cavitation (up to 24%).Item Comparative Assessment of Non-newtonian Single-Phase and Two-Phase Approaches for Numerical Studies of Centrifugal Pumps Handling Emulsion(Springer Nature, 2024) Achour, Lila; Specklin, Mathieu; Asuaje, Miguel; Kouidri, Smaine; Belaidi, IdirComputational Fluid Dynamics is commonly employed to assess the effect of oil-water emulsions on pump performance, usually using two-phase models. However, these models often neglect the emulsion’s non-Newtonian behavior, despite its known experimental significance in enhancing pump performance. This study attempts to evaluate both single-phase non-Newtonian and two-phase approaches to model emulsion flow within centrifugal pumps. The non-Newtonian single-phase and several two-phase models are evaluated by comparing the predicted pump heads with experimental data of a multistage pump from the literature. The findings show that the non-Newtonian single-phase model generally provides better agreement with experimental measurements, particularly for emulsions with low dispersed phase fractions. Nevertheless, for emulsions with a high dispersed phase fraction (≈ 50%), the difference between the two approaches is insignificant. Thus, due to the lack of a universal multiphase model for emulsion simulation, the non-Newtonian single-phase model can serve as a viable alternative, overcoming the limitations of two-phase approaches in simulating complex multiphase fluid systems.Item Relationship between structural and mechanical properties of polyethylene matrix nanocomposites(Faculty of Engineering, Khon Kaen University, 2024) Rahmaoui, Fath Eddine Zakaria; Belaidi, IdirThis study examined the impact of incorporating graphene nanoplatelets (GnP) into high-density polyethylene (PE) to create nanocomposites, with and without a compatibiliser. We specifically focused on the impact of structural crystallinity on the mechanical properties of the nanocomposites. These nanocomposites exhibited a much higher Young's modulus compared with pure PE. Specifically, the Young’s modulus increased exponentially with the addition of a compatibiliser and linearly without it. One explanation for this exponential rise in Young's modulus is that the crystal's compacted polymer chain structure improved its stiffness, facilitating effective load transfer. Additionally, a poor distribution of GnP in the nanocomposites with a filler content of 0.5 and 1 wt.%, both with and without a compatibiliser, led to a decreased stress and strain at break. However, at higher filler contents, well-distributed GnP play a key role in enhancing stress and strain at break.Item A review of emulsion flows, their characterization and their modeling in pumps(Institution of Chemical Engineers, 2024) Achour, Lila; Specklin, Mathieu; Asuaje, Miguel; Kouidri, Smaine; Belaidi, IdirIn the engineering field, emulsions and liquid–liquid two-phase flows within centrifugal pumps are generally unwanted as emulsions will have negative effects on pump operation. Besides, emulsions are usually formed when the oil and water phases are brought together in a process called emulsification, which is enhanced by high shear rates. This topic has been extensively researched over the past decades, with sophisticated theories regarding the phenomena involved in emulsions formation and characterization in pumps. Besides, given the complexity of the physics governing emulsions, studies on their modeling within pumps, based on empirical correlations or computational fluid dynamics models, are insufficient and remain limited. This review aims to provide a complete overview of investigations on liquid–liquid flow in centrifugal pumps. Characteristics of these mixtures, such as stability, phase inversion, droplet size distribution and rheological behavior, are discussed. Current approaches and techniques for analyzing pump performance handling emulsion and two-phase liquid–liquid flow are reviewed thoroughly. The limitations of the existing models are studied, and potential future developments are proposed.Item Prediction of the peak load and absorbed energy of dynamic brittle fracture using an improved artificial neural network(Elsevier, 2022) Oulad Brahim, Abdelmoumin; Belaidi, Idir; Fahem, Noureddine; Khatir, Samir; Mirjalili, Seyedali Jamal; Abdel Wahab, Magd M.In this paper, a robust technique is presented to predict the peak load and crack initiation energy of dynamic brittle fracture in X70 steel pipes using an improved artificial neural network (IANN). The main objective is to investigate the behaviour of API X70 steel based on two experimental tests, namely Drop Weight Tear Test (DWTT) and the Charpy V-notch impact (CVN), for steel pipe specimens. The mechanical properties in the brittle fracture behaviour of API X70 steel pipes are predicted utilizing numerical approaches with different crack lengths. Next, to simulate the impact of API X70 steel pipes at lower temperatures through a numerical approach, a cohesive approach using the extended Finite Element Method (XFEM) is used. The data obtained are used as input for the proposed IANN using Balancing Composite Motion Optimization (BCMO), Particle Swarm Optimization (PSO) and Jaya optimization algorithms, to predict the peak load values and crack initiation energy of dynamic brittle fractures in API X70 steel with different crack lengths. The results show the effectiveness of ANN-PSO and ANN-BCMO based on the convergence of the results and the accuracy of the prediction of the peak load and crack initiation energy.Item A new methodology to predict the sequence of GFRP layers using machine learning and JAYA algorithm(Elsevier, 2023) Fahem, Noureddine; Belaidi, Idir; Oulad Brahim, Abdelmoumin; Capozucca, Roberto; Thanh, Cuong Le; Khatir, Samir; Abdel Wahab, Magd M.In this paper, the best stacking sequence using experimental tests of GFRP composites is investigated. The main objective of this work is to determine the main specification of GFRP composite material, which is represented by its physics-mechanical properties, weight, and cost, before performing a series of experimental tests based on various stacking sequences. Our methodology is divided into three stages. The first stage is characterized by extracting the bending data from mechanical tests of some GFRP composites. In the second stage, the validated numerical model is used to simulate numerous cases of stacking sequences. In the last stage, the extracted data is used to determine the parameters for different stacking sequences using an inverse technique based on ANN and JAYA algorithm. The results provide a good prediction of parameters as well as a good orientation to make decisions on the best GFRP stacking sequence to be used, according to the required specifications of the manufacturer.Item The Optimal Values of Hashin Damage Parameters Predict Using Inverse Problem in a CFRP Composite Material(Springer, 2024) Fahem, Noureddine; Belaidi, Idir; Aribi, Chouaib; Zara, Abdeldjebar; Khatir, Tawfiq; Oulad Brahim, Abdelmoumin; Capozucca, RobertoThe ever-increasing demand for advanced composite materials in industries like aerospace and automotive has spurred the drive to address their inherent weaknesses. This pursuit is facilitated by the availability of numerical simulations and artificial intelligence, offering a cost-effective means to comprehensively study various phenomena without excessive reliance on experimentation. While existing models in the scientific realm provide a foundation for composite material modeling, achieving results closely aligned with experimental data is often challenging due to the variation of the parameters and conditions. This present study introduces an innovative approach aimed at optimizing composite material performance and minimizing discrepancies between experimental and numerical outcomes. This approach leverages sophisticated optimization algorithms to fine-tune the Hashin damage parameters, resulting in a highly accurate model. Furthermore, the incorporation of an Artificial Neural Network (ANN) via an inverse problem based on Jaya’s algorithm solving strategy facilitates the prediction of optimal parameters, ensuring a significant reduction in error. This novel methodology presents a promising avenue for elevating the efficiency and reliability of CFRP composite materials in practical applications.Item A reduced-order method with PGD for the analysis of dynamically loaded journal bearing(2022) Megdoud, Abdelhak; Manser, Belkacem; Belaidi, Idir; Bakir, Farid; Khelladi, SofianeMachine component design has become a prominent topic for researchers in recent years. The analysis of bearing systems has received considerable attention in order to avoid detrimental contact. Among the most important studies in this area are the transient problems of journal bearings, which are usually performed by coupling the Reynolds equation with the motion equations. Many techniques have been presented in the literature and are still being explored to ensure the accurate findings and efficient solution prediction of unsteady state Reynolds equation. In this paper, the Proper Generalized Decomposition (PGD) approach is expanded for the analysis of the lubricant behavior of dynamically loaded journal bearing considering Swift-Stieber boundary conditions. The PGD model is applied in this problem, seeking the approximate solution in its separated form of the partial differential Reynolds equation at each time step during the load applied cycle employing the alternating direction strategy. Compared to the classical resolution, the PGD solution has a considerably low computational cost. To verify the accuracy and efficiency of this approach, three cases have been considered, infinitely short, infinitely long and finite journal bearings under the dynamic load. The results of the suggested methodology when compared to the full discretized model (FDM) show that, the new scheme is more efficient, converges quickly, and gives the accurate solutions with a very low CPU time consumption.Item A reduced-order method with PGD for the analysis of mis- aligned journal bearing(2021) Megdoud, Abdelhak; Manser, Belkacem; Belaidi, Idir; Bakir, Farid; Khelladi, Sofianen recent years, machine component design has been a major con- cern for researchers. Emphasis has been placed especially on the analysis of bearing systems in order to avoid detrimental contact. The shaft misalignment is one of the most problems that affects directly the operating conditions of these components. In this context, the present study proposes a reduced-order method "Proper Generalized Decomposition" (PGD) using the separation tech- nique through the alternating direction strategy to solve the modified Reynolds equation, taking into account the presence of misalignment in the shafting sys- tem. The solution shows the representation of two types of misalignment ge- ometry, especially axial and twisting. A comparison of the results between the proposed approach and the classical method, through several benchmark ex- amples, made it possible to highlight that the new scheme is more efficient, converges quickly and provides accurate solutions, with a very low CPU time expenditure.Item Numerical study of the performance loss of a centrifugal pump carrying emulsion(2021) Achour, Lila; Mathieu, Specklin; Belaidi, Idir; Kouidri, SmaineThe performance and hydrodynamic behavior of cen- trifugal pumps when handling two-phase liquid-liquid flow and emulsion remain relatively unexplored, al- though they are of fundamental importance in optimiz- ing the operating conditions of these pumps. Hence, this study aims at investigating the performance degra- dation of a centrifugal pump under emulsion flow by combined means of analytical and computational fluid dynamic (CFD) models. The analytical approach is based on internal energy loss equations while the CFD approach models the emulsion as a continuous and ho- mogeneous single-phase fluid exhibiting shear thinning behavior. The results give a good insight into the per- formance degradation of such a system, especially at the best efficiency point (BEP).