Yazar "Chamkha, Ali J." seçeneğine göre listele

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    Effects of two-phase nanofluid model and localized heat source/sink on natural convection in a square cavity with a solid circular cylinder
    (Elsevier Science Sa, 2019) Alsabery, Ammar, I; Gedik, Engin; Chamkha, Ali J.; Hashim, Ishak
    In the present study, natural convection heat transfer of Al2O3-water nanofluid inside a square cavity with a solid circular cylinder is investigated numerically. For numerical computations, the finite element method is used by taking into consideration Buongiorno's two-phase model. Parts of the vertical surfaces of cavity are kept at constant temperature (left wall T-h and right wall T-c) while the other walls (horizontal walls and the remaining of the vertical walls) are taken as adiabatic. The effects of some pertinent parameters such as the Rayleigh number (10(3) <= Ra <= 10(6)), nanoparticle volume fraction (0 <= phi <= 0.04), thermal conductivity of the solid cylinder (k(w) = 0.28, 0.76, 1.95, 7 and 16), radius of solid cylinder (0.1 <= R <= 0.4), heat source/sink length (0.2 <= D <= 0.8), and the heat source/sink position (0.2 <= B <= 0.8) on the fluid flow and heat transfer characteristics are investigated. The obtained numerical results are depicted graphically and discussed in detail from the point of view of the streamlines, isotherms, nanoparticle volume fractions and the local and average Nusselt number Nu. It is indicated that the heat transfer is enhanced with an increase in the nanoparticle volume fraction for all studied Rayleigh numbers. Furthermore, the thermal conductivity, solid circular cylinder size, D and B parameters are the key factors to control and optimize the heat transfer inside the cavity that is partially heated and cooled. The proposed method is found to be in good agreement between previously published experimental and numerical results. (C) 2018 Elsevier B.V. All rights reserved.
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    Impacts of heated rotating inner cylinder and two-phase nanofluid model on entropy generation and mixed convection in a square cavity
    (Springer, 2020) Alsabery, Ammar I.; Gedik, Engin; Chamkha, Ali J.; Hashim, Ishak
    A numerical study is carried out on mixed convection and entropy generation of Al2O3/water nanofluid due to a rotating cylinder inside a square cavity. The numerical computations are performed taking the non-homogenous model of Buongiorno into consideration. The inner moving rotating circular cylinder is maintained at a constant hot temperature T-h and the other left and right vertical walls of the cavity are maintained at a constant cold temperature T-c. The bottom and top horizontal walls are maintained as adiabatic. The Galerkin weighted residual method is implemented to numerically solve the governing equations. The Rayleigh number (10(4) <= Ra <= 10(7)), angular rotational velocity (0 <=omega <= 600) nanoparticles loading (0 <= phi <= 0.04) and the dimensionless radius of rotating cylinder (0.1 <= R <= 0.4) are the governing parameters of this study. Numerical results for the streamlines, isotherms, isentropic lines, nanoparticle loading, local and average Nusselt number and Bejan number are obtained and presented graphically. A detailed discussion of the results is performed to highlight the physics of the problem.
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    Transient nanofluid flow and energy dissipation from wavy surface using magnetic field and two rotating cylinders
    (Pergamon-Elsevier Science Ltd, 2021) Alsabery, Ammar I.; Ismael, Muneer A.; Gedik, Engin; Chamkha, Ali J.; Hashim, Ishak
    The problem of transient Magnetohydrodynamic (MHD) combined convection within a wavy-heated rectangular cavity having two inner cylinders is investigated using the non-homogeneous nanofluid scheme. The lower wavy surface of the cavity is kept at a constant hot temperature (T-h) while the upper flat surface is kept at a constant cold temperature (T-c). The remaining surfaces (vertical surfaces) are maintained adiabatic. An Al2O3/water nanofluid is filled inside the cavity and a non-homogeneous approach is adopted to solve governing equations by using the Galerkin method. The effect of some parameters such as the angular rotational speed, the volume fraction of nanoparticles, Hartmann number on the flow and heat transfer characteristics are examined. The results indicate that the waving of the hot base of the cavity enhances the Nusselt number. The maximal Nusselt numbers are obtained when the number of undulations N is 2, where the Nusselt number augments by 18% when N is boosted from 0 to 2 and by 16% from 0 to and 5. Also, the outcomes reveal that the enhancement of the Nusselt number as a result of raising the rotational speed of the two cylinders from 0 to +/- 500 is about 315%.