Browsing by Author "Saci, Rachid"

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    Flows characteristics of two immiscible swirling fluids in a cylinder
    (Mechanika, 2024) Brahma, Kenza; Saci, Rachid; Mansouri, Kacem; Imoula, Malika
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    Mechanical Properties of Alfa, Sisal, and Hybrid Alfa/Sisal Fiber Satin Cloth Reinforced Epoxy
    (Springer Nature, 2024) Baali, Besma R.; Gherbi, Mohammed Tahar; Nour, Abdelkader; Casimir, J.B.; Saci, Rachid; Aguib, Salah; Attia, Nourhane; Aribi, Chouaib
    The mechanical behavior of composites, made of an epoxy resin matrix reinforced by 30 and 40% of a satin cloth from long Alfa, sisal and hybrid Alfa/sisal fibers was studied. The fibers are obtained by extraction with elimination of binders such as pectins and lignin. For each type of fibers, appropriate and optimal chemical and thermal treatments were conducted within NaOH solution, to enhance both the fiber surface quality and the interfacial bonding between fibers and matrix. Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and chemical decomposition of treated and untreated fibers lead to prove the treatment efficiency. The thermogravimetric (TGA) and differential thermogravimetric (DTG) analyses showed better thermal stability. Differential scanning calorimetry (DSC) made it possible to quantify the enthalpy changes which showed an increase in the amount of heat as a function of the increase in weight fraction of natural fibers. The endothermic reaction of the composites studied containing 30 wt% fiber reinforcement was less than that containing 40 wt% fiber reinforcement. The composite materials were produced by vacuum assisted resin transfer molding (VARTM) method due to hydrophilic nature of the fibers. The results of static tests were compared to those of pure epoxy resin. It showed a significant increase for 40 wt% woven A1lfa/epoxy of about 333, 113, and 81% in tension, 3-points bending and compression tests respectively. SEM morphology analysis revealed good interfacial adhesion between the treated fibers and the matrix.
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    Swirling flows characteristics in a cylinder under effect of buoyancy
    (Kauno Technologijos Universitetas, 2021) Fekhar, Mustafa; Saci, Rachid; Gatignol, Renée
    Thermal buoyancy, induced by injection or by dif-ferential heating of a tiny rod is explored to control break-down in the core of a helical flow driven by the lid rotation of a cylinder. Three main parameters are required to charac-terize numerically the flow behavior; namely, the rotational Reynolds number Re, the cavity aspect ratio and the Richardson number Ri. Warm injection/rod, Ri > 0, is shown to prevent on-axis flow stagnation while breakdown en-hancement is evidenced when Ri [removed] 0). Besides, the emergence of such a toroidal mode was not found to occur under thermal stratification induced by a differentially heated rod. Moreover, three state dia-grams were established which provide detailed flow charac-teristics under the distinct and combined effects of buoy-ancy strength, viscous effects and cavity aspect ratio
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    Vortex breakdown control in confined swirling flows
    (2008) Saci, Rachid; Kouadri, Amar
    Confined steady flows, which display on-axis or off-axis vortex breakdown, have been numerically studied, with particular attention focused on means of controlling the vortex breakdown bubbles. Firstly, the model flow driven by one end disk of a cylindrical enclosure, which exhibits two distinct on-axis vortex bubbles, has been considered. The resulting computations revealed that, sloping slightly the stationary sidewall, beyond a threshold angle, provided an effective means of removing the secondary vortex structure, and the flow remains steady. Besides, this technique is shown to significantly modify the flow topology which displays off-axis bubbles, induced by the co-rotation of the end disks. Then, the effectiveness of adding a near-axis swirl, as suggested in recent experimental works, has been analysed numerically and found to substantially alter on-axis reverse flows
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    Vortex characteristics of two rotating immiscible fluids
    (2023) Brahma, Kenza; Saci, Rachid; Mansouri, Kacem
    Hydrodynamic and behavior of laminar confined axisymmetric flows driven by the rotating top disk in cylindrical cavity have been studied numerically. The vertical cavity, is filled with two superposed immiscible incompressible fluids. The top more viscous liquid drives the lower heavier fluid via the interface shear. The study, identified and highlighted a flow topology of types of axisymmetric recirculation regions; depending upon the effects of the disk rotation rate. This work confirms partly previous experimental observations and provides additional quantitative findings; particularly in the vicinity of the interface. The findings are in good accord with the experiments and show that vortex size increases with increasing rotation rate. The basic flow is made up of two clockwise circulation cells, separated by a thin layer of anticlockwise circulation (TCL). The gap thickness of TCL decreases with increasing rotation rate however, the interface high increases as rotation rate increases