Browsing by Author "Fekhar, Mustafa"

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    Effects of density on coaxial swirling jets characteristics
    (Université M'Hamed Bougara : Faculté de Technologie, 2022) Fekhar, Mustafa; Saci, Rachid(Directeue de thèse)
    Thermal buoyancy, induced by injection or by differential heating of a rod, is explored to control breakdown onset which occurs in the core of a helical flow driven by the lid rotation of a vertical cylinder. Three main parameters are required to characterize numerically the flow behavior; namely, the rotational Reynolds number Re , the cavity aspect ratio ? and the Richardson number Ri . Warm injection/rod, 0 Ri ? , is shown to prevent on-axis flow stagnation while breakdown enhancement is evidenced when 0Ri ? . In addition, when 0 Ri ? , results revealed that a bubble vortex evolves into a ring type structure which may remain robust, as observed in prior related experiments or, in contrast, disappear over a given range of parameters ( 0 ) ,, i R e R ?? . 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 diagrams were established which provided detailed flow characteristics under the distinct and combined effects of buoyancy strength, viscous effects and cavity aspect ratio
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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