The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Hakan F Oztop - One of the best experts on this subject based on the ideXlab platform.
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mhd natural convection and entropy generation of ferrofluid in an open trapezoidal cavity partially filled with a porous medium
International Journal of Mechanical Sciences, 2018Co-Authors: Marina S Astanina, Hakan F Oztop, Mikhail A Sheremet, Nidal AbuhamdehAbstract:Abstract In this study, natural convection combined with entropy generation of Fe3O4–water nanofluid within an open trapezoidal cavity filled with a porous layer and a ferrofluid layer under the effect of uniform Inclined magnetic field is numerically analyzed. Porous layer is located on the bottom Wall and heated from the left Inclined Wall. Bottom Wall, right and left tilted Walls of the cavity are adiabatic except for the active part along the left Inclined Wall where hot temperature Th is constant, upper open boundary is kept at constant cold temperature Tc. Governing equations with corresponding boundary conditions formulated in dimensionless stream function and vorticity using Brinkman-extended Darcy model for porous layer have been solved numerically using finite difference method. Numerical analysis has been carried out for a wide range of Hartmann number, magnetic field inclination angle, height of the porous layer and nanoparticles volume fraction. It has been found that an increase in Hartmann number leads to a growth of oscillations amplitude for average Nusselt number and average entropy generation. At the same time inclination angle α = π/2 illustrates unstable behavior of heat and fluid flow.
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Magnetohydrodynamic natural convection in trapezoidal cavities
International Communications in Heat and Mass Transfer, 2012Co-Authors: Hasanuzzaman, Hakan F Oztop, Mustafizur Rahman, Nasrudin Abdul Rahim, Rahman Saidur, Yasin VarolAbstract:Abstract A computational numerical work has been done to see the effects of magnetic field on natural convection for a trapezoidal enclosure. Both Inclined Walls and bottom Wall have constant temperature where the bottom Wall temperature is higher than the Inclined Walls. Top Wall of the cavity is adiabatic. To investigate the effects, finite element method is used to solve the governing equations for different parameters such as Rayleigh number, Hartmann number and inclination angle of Inclined Wall of the enclosure. It is found that heat transfer decreased by 20.70% and 16.15% as φ increases from 0 to 60 at Ra = 10 5 and 10 6 respectively. On the other hand, heat transfer decreased by 20.28% and 13.42% as Ha increases from 0 to 50 for Ra = 10 5 and 10 6 respectively.
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natural convection in right angle porous trapezoidal enclosure partially cooled from Inclined Wall
International Communications in Heat and Mass Transfer, 2009Co-Authors: Yasin Varol, Hakan F OztopAbstract:Abstract A numerical study is conducted to investigate the steady free convection flow in a two-dimensional right-angle trapezoidal enclosure filled with a fluid-saturated porous medium. The left vertical Wall of the cavity is heated; the Inclined Wall is partially cooled; and the remaining Walls are insulated (adiabatic). Three different cases are considered. While in Case I the cooler Wall is located adjacent to the top Wall, in Case II it is located in the middle Inclined Wall. In Case III, it is located adjacent to the bottom Wall. Flow and heat transfer characteristics are studied for a range of parameters: the Rayleigh number, Ra, 100 ≤ Ra ≤ 1000; and the aspect ration, AR = 0.25, 0.50 and 0.75. Numerical results indicate that there exist significant changes in the flow and temperature fields as compared with those of a differentially heated square porous cavity. These results lead, in particular, to the prediction of a position of minimum heat transfer across the cavity, which is of interest in the thermal insulation of buildings and other areas of technology.
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Effects of Wall conduction on natural convection in a porous triangular enclosure
Acta Mechanica, 2008Co-Authors: Hakan F Oztop, Yasin VarolAbstract:Conjugate natural convection in a two-dimensional triangular enclosure filled with a porous medium is examined in this article. It is assumed that the solid vertical Wall is of finite conductivity and that the temperature of the Inclined Wall is lower than that of the vertical Wall, while the horizontal Wall is adiabatic. A finite difference method is used to solve the governing equations of convection and conduction for different parameters as Rayleigh number, width of the vertical solid Wall, aspect ratio of the enclosure and thermal conductivity ratio between solid and porous media. It is found that heat transfer increases with increasing Rayleigh number and aspect ratio of the triangle, decreasing Wall thickness and with the increase of the Wall conductivity.
Yasin Varol - One of the best experts on this subject based on the ideXlab platform.
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Magnetohydrodynamic natural convection in trapezoidal cavities
International Communications in Heat and Mass Transfer, 2012Co-Authors: Hasanuzzaman, Hakan F Oztop, Mustafizur Rahman, Nasrudin Abdul Rahim, Rahman Saidur, Yasin VarolAbstract:Abstract A computational numerical work has been done to see the effects of magnetic field on natural convection for a trapezoidal enclosure. Both Inclined Walls and bottom Wall have constant temperature where the bottom Wall temperature is higher than the Inclined Walls. Top Wall of the cavity is adiabatic. To investigate the effects, finite element method is used to solve the governing equations for different parameters such as Rayleigh number, Hartmann number and inclination angle of Inclined Wall of the enclosure. It is found that heat transfer decreased by 20.70% and 16.15% as φ increases from 0 to 60 at Ra = 10 5 and 10 6 respectively. On the other hand, heat transfer decreased by 20.28% and 13.42% as Ha increases from 0 to 50 for Ra = 10 5 and 10 6 respectively.
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natural convection in right angle porous trapezoidal enclosure partially cooled from Inclined Wall
International Communications in Heat and Mass Transfer, 2009Co-Authors: Yasin Varol, Hakan F OztopAbstract:Abstract A numerical study is conducted to investigate the steady free convection flow in a two-dimensional right-angle trapezoidal enclosure filled with a fluid-saturated porous medium. The left vertical Wall of the cavity is heated; the Inclined Wall is partially cooled; and the remaining Walls are insulated (adiabatic). Three different cases are considered. While in Case I the cooler Wall is located adjacent to the top Wall, in Case II it is located in the middle Inclined Wall. In Case III, it is located adjacent to the bottom Wall. Flow and heat transfer characteristics are studied for a range of parameters: the Rayleigh number, Ra, 100 ≤ Ra ≤ 1000; and the aspect ration, AR = 0.25, 0.50 and 0.75. Numerical results indicate that there exist significant changes in the flow and temperature fields as compared with those of a differentially heated square porous cavity. These results lead, in particular, to the prediction of a position of minimum heat transfer across the cavity, which is of interest in the thermal insulation of buildings and other areas of technology.
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Effects of Wall conduction on natural convection in a porous triangular enclosure
Acta Mechanica, 2008Co-Authors: Hakan F Oztop, Yasin VarolAbstract:Conjugate natural convection in a two-dimensional triangular enclosure filled with a porous medium is examined in this article. It is assumed that the solid vertical Wall is of finite conductivity and that the temperature of the Inclined Wall is lower than that of the vertical Wall, while the horizontal Wall is adiabatic. A finite difference method is used to solve the governing equations of convection and conduction for different parameters as Rayleigh number, width of the vertical solid Wall, aspect ratio of the enclosure and thermal conductivity ratio between solid and porous media. It is found that heat transfer increases with increasing Rayleigh number and aspect ratio of the triangle, decreasing Wall thickness and with the increase of the Wall conductivity.
G. E. Sims - One of the best experts on this subject based on the ideXlab platform.
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Experimental investigation of two-phase discharge from a stratified region through a small branch mounted on an Inclined Wall
International Journal of Multiphase Flow, 2010Co-Authors: J.t. Bartley, Hassan M. Soliman, G. E. SimsAbstract:Abstract Experimental data are presented for the mass flow rate and quality of two-phase discharge through a small branch of diameter d (=6.35 mm) attached normally to an Inclined flat plane. The flat plane was situated in a large tank containing a stratified mixture of air and water under pressure (316 kPa) and at room temperature. The plane was Inclined through various angles ( θ ) in increments of 30°, from the outlet-branch orientation being vertically upward through the horizontal to vertically downward. The bulk of the data correspond to seven inclination angles and two test-section-to-separator pressure differences (Δ P ) of 11.0 and 115.5 kPa, and for each combination of θ and Δ P , the mass flow rate and quality were measured at different values of the interface level ( h ) between the onsets of gas and liquid entrainment. Four additional data sets were generated for other values of Δ P in order to confirm certain trends. Influences of these independent variables on the mass flow rate and quality are discussed and normalized plots are presented showing that the data can be collapsed for a wide range of conditions. Comparisons are made between the present data and previous correlations/models and new empirical correlations are formulated and shown to be capable of predicting the present data with good accuracy.
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experimental investigation of the onsets of gas and liquid entrainment from a small branch mounted on an Inclined Wall
International Journal of Multiphase Flow, 2008Co-Authors: J.t. Bartley, Hassan M. Soliman, G. E. SimsAbstract:Abstract The phenomena of the onsets of liquid entrainment and gas entrainment were investigated experimentally for the case of a flat plane with a circular outlet branch of diameter d (=6.35 mm) at the plane centre. This flat plane was situated in a large tank containing a stratified mixture of air and water under pressure (317 kPa for most experiments and 520 kPa for a few experiments) and at room temperature. The plane was Inclined through various angles (θ) in increments of 30°, from the outlet branch orientation being vertically upward through the horizontal to vertically downward. For both onsets the vertical distance between the centre of the outlet branch and the undisturbed gas–liquid interface (h) was measured for various angles of inclination and Froude numbers. Both onsets were observed visually through a large viewing part of the test section. It was found that for both onsets there is a range of inclination angles where the onset h depended on θ and a range where the onset h essentially did not depend on θ. The data were correlated in terms of onset h/d, Froude number, and θ where there was dependence of onset h on the angle of inclination.
Roger G Horn - One of the best experts on this subject based on the ideXlab platform.
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effect of disjoining pressure on terminal velocity of a bubble sliding along an Inclined Wall
Journal of Colloid and Interface Science, 2011Co-Authors: Lorena A Del Castillo, Satomi Ohnishi, Lee R White, Steven L Carnie, Roger G HornAbstract:Abstract The influence of salt concentration on the terminal velocities of gravity-driven single bubbles sliding along an Inclined glass Wall has been investigated, in an effort to establish whether surface forces acting between the Wall and the bubble influence the latter’s mobility. A simple sliding bubble apparatus was employed to measure the terminal velocities of air bubbles with radii ranging from 0.3 to 1.5 mm sliding along the interior Wall of an Inclined Pyrex glass cylinder with inclination angles between 0.6 and 40.1°. Experiments were performed in pure water, 10 mM and 100 mM KCl solutions. We compared our experimental results with a theory by Hodges et al. [1] which considers hydrodynamic forces only, and with a theory developed by two of us [2] which considers surface forces to play a significant role. Our experimental results demonstrate that the terminal velocity of the bubble not only varies with the angle of inclination and the bubble size but also with the salt concentration, particularly at low inclination angles of ∼1–5°, indicating that double-layer forces between the bubble and the Wall influence the sliding behavior. This is the first demonstration that terminal velocities of sliding bubbles are affected by disjoining pressure.
Akio Miyara - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation of wavy liquid film flowing down on a vertical Wall and an Inclined Wall
International Journal of Thermal Sciences, 2000Co-Authors: Akio MiyaraAbstract:Abstract Interfacial wave behavior and flow characteristics of falling liquid films on a vertical Wall and an Inclined Wall have been studied by means of a numerical simulation, in which the algorithm is based on MAC method. Basic equations are discretized on a staggered grid fixed on a physical space. Interfacial boundary conditions are treated with a newly proposed method and the wave behavior can be calculated accurately. Simulation results agree well with experimental observations. For both the simulation and the experiment of the vertical Wall, a low-frequency disturbance develops to a solitary wave, which is a big-amplitude wave accompanied by small-amplitude short capillary waves. In the big wave, a circulation flow generates and grows downstream, in which the scale of the circulation flow is comparable to the wave amplitude, while there is no circulation in the capillary waves. Although waves on the slightly Inclined Wall develop to the solitary wave, no circulation flow appears in the big wave because of the gravitational effect. Increasing the frequency, the wave amplitude becomes small and accompanied capillary waves disappear. In a certain frequency, the circulation flow repeats generation and collapse due to the wave interaction.
