Department of Mathematics

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https://escholar.umt.edu.pk/handle/123456789/348

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Browsing Department of Mathematics by Author "Ahmer Mehmood"

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    Entropy generation in hydrodynamic slip flow over a vertical plate with convective boundary
    (Springer, 2012) Adnan Saeed Butt; Sufian Munawar; Asif Ali; Ahmer Mehmood
    The present article aims to report the effects of hydrodynamic slip on entropy generation in the boundary layer flow over a vertical surface with convective boundary condition. Suitable similarity transformations are used to transform the fundamental equations of hydrodynamic and thermal boundary layer flow into ordinary differential equations. The governing equations are then solved numerically using the shooting method and the velocity and the temperature profiles are obtained for various values of parameters involved in the governing equations. The expressions for the entropy generation number and the Bejan number are presented and the results are discussed graphically and quantitatively for the slip parameter, the local Grashof number, the Prandtl number, the local convective heat transfer parameter, the group parameter and the local Reynolds number. It is observed that due to the presence of slip, entropy production in a thermal system can be controlled and reduced.
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    Thermal analysis of the flow over an oscillatory stretching cylinder
    (IOP Publishing, 2012) Sufian Munawar; Asif Ali; Ahmer Mehmood
    An investigation has been conducted on the convective heat transfer and the entropy production attributable to the presence of an infinitely long cylinder in a viscous fluid exhibiting oscillatory motion. The heat transfer analysis is carried out by assuming that the surface of the cylinder is isothermal. The entropy generation is caused by heat transfer attributable to the finite temperature difference MT and viscous effects produced in the fluid. The number of independent variables in the governing equations is reduced by using a proper set of similarity variables. To obtain the solution of the nonlinear partial differential equation, we use a well-known finite difference scheme by transforming the semi-infinite domain to a finite domain. The numerical results have been analyzed by means of a comprehensive parametric study. It is observed that the entropy production intensifies in the presence of the oscillatory motion of the cylinder.
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    Time-dependent flow and heat transfer over a stretching cylinder
    (The Physical Society of Republic of China, 2012) Sufian Munawar; Ahmer Mehmood; Asif Ali
    The unsteady laminar boundary-layer flow and heat transfer of a viscous fluid over a stretching cylinder is discussed in this work. To normalize the governing system of equations a proper set of similarity variables is used. Two types of thermal boundary conditions, prescribed surface temperature (PST) and prescribed heat flux (PHF), are taken into account for thermal analysis. The governing equations are solved using the homotopy analysis method, and the obtained series solution is found to be valid for the entire temporal and spatial domains and for certain ranges of the other physical parameters. The effects of various material parameters on different physical quantities, such as the coefficient of skin friction and the Nusselt number, are illustrated through graphs and tables.
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    Time-dependent stagnation-point flow over rotating disk impinging oncoming flow
    (Shanghai University and Springer-Verlag, 2013) Sufian Munawar; Ahmer Mehmood; Asif Ali
    The unsteady stagnation point flow of an incompressible viscous fluid over a rotating disk is investigated numerically in the present study. The disk impinges the oncoming flow with a time-dependent axial velocity. The three-dimensional axisymmetric boundary-layer flow is described by the Navier-Stokes equations. The governing equations are solved numerically, and two distinct similarity solution branches are obtained. Both solution branches exhibit different flow patterns. The upper branch solution exists for all values of the impinging parameter and the rotating parameter . However, the lower branch solution breaks down at some moderate values of . The involvement of the rotation at disk allows the similarity solution to be transpired for all the decreasing values of . The results of the velocity profile, the skin friction, and the stream lines are demonstrated through graphs and tables for both solution branches. The results show that the impinging velocity depreciates the forward flow and accelerates the flow in the tangential direction.
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    Unsteady flow and heat transfer in a composite porous annulus with time-dependent injection
    (VERLAG Z NATURFORSCH, 2012) Muhammad Nasir; Sufian Munawar; Ahmer Mehmood; Asif Ali
    In the present study, we deal with the momentum and heat transfer analysis in a horizontal annulus of a composite porous medium. The Darcy–Brinkman model is used to develop the governing equations for the flow and heat transfer phenomenon. The annulus injects the time dependent oscillatory velocity normal to its surface. Both the regions of the flow have their own viscosities, and the heat transfer analysis is carried out by retaining viscous dissipation. The governing equations for flow and heat transfer are solved analytically using a perturbation series for solutions in both regions of the annulus. A brief parametric analysis is performed for the velocity and the temperature profiles through graphs.