Browsing by Author "Ismael M.A."

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    Mixed convection in a partially layered porous cavity with an inner rotating cylinder
    (Taylor and Francis Ltd., 2016) Chamkha A.J.; Selimefendigil F.; Ismael M.A.
    In this study, mixed convection in a cavity that has a fluid and superposed porous medium with an adiabatic rotating cylinder is numerically investigated. The bottom horizontal wall is heated and the top horizontal wall is cooled while the remaining walls are assumed to be adiabatic. An adiabatic rotating cylinder is inserted inside the cavity. The governing equations are solved by the Galerkin weighted residual finite element method. The effects of Rayleigh number (between 103 and 106), angular rotational speed of the cylinder (between 0 and 6,000), Darcy number (between 10-5 and 10-2), cylinder sizes (between R = 0.1 and R = 0.3) and three different vertical locations of the cylinder on the fluid flow and heat transfers characteristics are numerically investigated. It is observed that the cylinder size has a profound effect on the local and averaged heat transfer. The local and averaged heat transfers generally increase and the convection is more effective in the upper half of the cavity as the Rayleigh number and Darcy number enhance. The averaged heat transfers increases with the cylinder size until Ra = 105. The averaged heat transfer increases almost linearly with the angular rotational velocity of the cylinder and the increase rate becomes higher as the cylinder size increases. The local and averaged heat transfers enhances/deteriorate as the cylinder approaches the upper/lower wall of the cavity. Copyright © Taylor & Francis Group, LLC.
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    Mixed convection in a vertically layered fluid-porous medium enclosure with two inner rotating cylinders
    (Begell House Inc., 2017) Ismael M.A.; Selimefendigil F.; Chamkha A.J.
    In this study, mixed convection in a vertically half partitioned cavity with two rotating adiabatic cylinders is numerically investigated. The horizontal walls are thermally insulated. The left vertical wall is kept isothermally at high temperature while the right vertical wall is kept isothermally at lower temperature. The Galerkin weighted residual finite element method is used to solve the governing equations. The numerical study is performed for various values of Rayleigh numbers (between 103 and 106), angular rotational speed of the cylinders (between -5000 and 5000), Darcy numbers (between 10-5 and 10-2), horizontal positions of the cylinder centers (between 0.4 and 0.6) and cylinder sizes (between 0.1 and 0.4). It is observed that angular velocity of the cylinders and cylinder sizes have a profound effect on the heat transfer enhancement along the hot vertical wall. The averaged heat transfer enhancements are 354.65% and 45.24% at a Rayleigh number of 106 compared to the case at a Rayleigh number of 103 for cylinder sizes of R = 0.1 and R = 0.4. Large variations in the local heat transfer are seen for various angular velocities of the cylinder, and cylinder rotation brings averaged heat transfer enhancement for sizes of R = 0.3 and R = 0.4. The averaged heat transfer enhances by 235.10% for a Darcy number of 10-2 compared to a Darcy number of 10-5 using cylinder sizes of R = 0.1. The horizontal movement of the cylinder centers increases the averaged heat transfer by 34.08% for (D1 = D2 = 0.6) compared to configuration at (D1 = D2 = 0.4) for angular rotational speed of Ω = -5000. © 2017 by Begell House, Inc.
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    Mixed convection in superposed nanofluid and porous layers in square enclosure with inner rotating cylinder
    (Elsevier Ltd, 2017) Selimefendigil F.; Ismael M.A.; Chamkha A.J.
    In this study, numerical simulation of mixed convection in a partitioned square cavity having CuO-Water nanofluid and superposed porous medium with an adiabatic rotating cylinder is performed. The bottom horizontal wall of the cavity is heated and the top horizontal wall is cooled while the remaining vertical walls are insulated. An adiabatic rotating cylinder is located at the center of the square cavity. Galerkin weighted residual finite element method is utilized to solve the governing equations of the system. The influence of Rayleigh number (between 103 and 106), angular rotational velocity of the cylinder (between 0 and 6000), solid volume fraction of the nanoparticle (between 0 % and 0.05 %), Darcy number (between 10−5 and 10−2) and three different vertical locations of the cylinder on the fluid flow and heat transfer characteristics are numerically investigated in detail for three different cylinder sizes. It is observed that the averaged heat transfer enhances as the value of Rayleigh number, angular rotational speed of the cylinder, nanoparticle volume fraction and Darcy number increase. The effect of the angular rotational speed of the cylinder on the averaged heat transfer enhancement is more pronounced for large cylinder size and 432.55% of averaged enhancement is achieved for Ω=6000 compared to motionless cylinder case at Ω=0 using cylinder sizes of R=0.3. The averaged heat transfer enhances almost linearly with nanoparticle volume fraction for different cylinder sizes and adding solid nanoparticles to the base fluid is favorable for the locations when high values of local Nusselt number is observed. Local and averaged Nusselt number enhance as the cylinder approaches to the upper wall of the cavity. © 2017 Elsevier Ltd