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Ioan Pop - One of the best experts on this subject based on the ideXlab platform.

  • mixed convection flow heat transfer species concentration near the Stagnation Point on a vertical flat plate with stefan coupled blowing
    2017
    Co-Authors: Natalia C Rosca, J H Merkin, Alin V Rosca, Ioan Pop
    Abstract:

    Purpose The purpose of this study is to consider the effects that buoyancy arising from the combination of both thermal and concentration gradients can have on the mixed convection boundary-layer flow near a Forward Stagnation Point with the effect of Stefan blowing being included. Ad suitable choice for the functional forms of the outer flow and the wall temperature and concentration enables the problem to be reduced to a similarity form involving the dimensionless parameters, λ (mixed convection), κ (Stefan blowing) and N (relative strength of concentration driven buoyancy to that of thermal driven), as well as the Prandtl and Schmidt numbers. Numerical solutions to this similarity system for a range of representative parameter values indicate a finite, non-zero range of κ where there can be four solutions in opposing flow with only one solution in aiding flow. Asymptotic solutions for large values of N and κ are derived, the latter having two different structures in the opposing flow. Design/methodology/approach This paper sets up a similarity problem to examine the effects of Stefan blowing on a mixed convection flow with the aims of solving the equations numerically and complementing the results with appropriate asymptotic analysis. Findings The findings of the study include multiple solution branches, saddle-node bifurcations and singularities appearing in the solution. Originality/value The authors believe that all the results, both numerical and asymptotic, are original and have not been published elsewhere.

  • mhd flow of a nanofluid at the Forward Stagnation Point of an infinite permeable wall with a convective boundary condition
    2016
    Co-Authors: Siti Hidayah Muhad Saleh, Roslinda Mohd Nazar, Norihan Md Arifin, Ioan Pop
    Abstract:

    The steady magnetohydrodynamic (MHD) flow of a nanofluid at the Forward Stagnation Point of an infinite permeable wall is investigated in this study. A mathematical model has been constructed and the governing partial differential equations are converted into ordinary differential equations by similarity transformation. The similarity equations are solved numerically by a shooting technique. Results for the surface shear stresses, surface heat transfer, and velocity, nanoparticle fraction and temperature profiles are presented in tables and in some graphs. Effects of the magnetic parameter , constant mass flux Biot number , Brownion motion parameter thermophoresis parameter and Lewis number are examined. The present results are compared with previously available numerical results obtained using other methods of solution, and they are found to be in good agreement.

  • the development of forced convection heat transfer near a Forward Stagnation Point with newtonian heating
    2012
    Co-Authors: J H Merkin, Roslinda Mohd Nazar, Ioan Pop
    Abstract:

    A mathematical model for the unsteady forced convection boundary-layer flow near a Forward Stagnation Point is considered when there is Newtonian heating on the surface whereby the heat transfer is proportional to the local surface temperature. In a previous paper (Salleh et al. J Eng Math 69:101–110, 2011), a critical value γ c, dependent on the Prandtl number σ, of the heat transfer coefficient γ was identified, with solutions for the corresponding steady problem possible only for γ < γ c. The unsteady problem considered here shows that these steady states are attained at large times when γ < γ c. For γ > γ c, the solution still continues to large time, now growing exponentially with time. This rate of growth is determined by an eigenvalue problem which we solve numerically for general values of γ and σ and asymptotically for large γ and both large and small σ.

  • forced convection boundary layer flow at a Forward Stagnation Point with newtonian heating
    2009
    Co-Authors: Mohd Zuki Salleh, Roslinda Mohd Nazar, Ioan Pop
    Abstract:

    The steady forced convection boundary layer flow near the Forward Stagnation Point of an infinite plane wall generated by Newtonian heating in which the heat transfer from the surface is proportional to the local surface temperature is investigated in this study. The governing partial differential equations are first transformed into a system of ordinary differential equations before they are solved numerically by a finite-difference scheme, namely the Keller box method. Numerical solutions are obtained for a large range of values of the Prandtl number.

  • series solution of unsteady boundary layer flows of non newtonian fluids near a Forward Stagnation Point
    2006
    Co-Authors: Shijun Liao, Ioan Pop
    Abstract:

    Abstract In this paper, the unsteady viscous flow of non-Newtonian fluids near the Forward Stagnation Point of a two-dimensional body is studied analytically. By using the homotopy analysis method, a convergent series solution is obtained, which is uniformly valid for all dimensionless time in the whole spatial region 0 ≤ η ∞ . Besides, the effects of integral power-law index of the non-Newtonian fluids on the flow are investigated. To the best of our knowledge, such kind of series solutions have never been reported for this problem.

Norsarahaida Amin - One of the best experts on this subject based on the ideXlab platform.

  • Unsteady mixed convection near the Forward Stagnation Point of a two-dimensional symmetric body
    2003
    Co-Authors: Roslinda Mohd Nazar, Norsarahaida Amin
    Abstract:

    The unsteady mixed convection boundary layer flow near the Forward Stagnation Point of a two-dimensional symmetric body resulting from an impulsive motion of the free stream velocity and by sudden increase in the surface temperature. The partial differential equations governing the flow and heat transfer have been solved numerically using Keller-box method. It is shown that there is a smooth transition from the unsteady initial flow (short time) to the final steady state flow(large time). It is also found that for the steady flow case that are dual solutions when the flow is opposing

  • unsteady boundary layer flow of a micropolar fluid near the Forward Stagnation Point of a plane surface
    2003
    Co-Authors: Yian Yian Lok, Norsarahaida Amin, P Phang, Ioan Pop
    Abstract:

    The growth of the boundary layer flow of a viscous and incompressible micropolar fluid started impulsively from rest near the rear Stagnation Point of a two-dimensional plane surface is studied theoretically. The transformed non-similar boundary-layer equations are solved numerically using a very efficient finite-difference method known as Keller-box method. This method may present well-behaved solutions for the transient (small time) solution up to the separation boundary layer flow. Numerical results are given for the reduced velocity and microrotation profiles, as well as for the skin friction coefficient when the material parameter K takes the values K=0 (Newtonian fluid), 0.5, 1, 1.1, 1.5, 2, 2.5 and 3 with the boundary condition for microrotation n=0 (strong concentration of microelements) and n=1/2 (weak concentration of microelements), respectively. Important features of these flow characteristics are shown on graphs and in tables

Nath G - One of the best experts on this subject based on the ideXlab platform.

  • Unsteady mhd flow and heat transfer on a rotating disk in an ambient fluid
    2002
    Co-Authors: Hs Takhar, Ak Singh, Nath G
    Abstract:

    An unsteady flow and heat transfer of a viscous incompressible electrically conducting fluid over a rotating infinite disk in an otherwise ambient fluid are studied. The unsteadiness in the flow field is caused by the angular velocity of the disk which varies with time. The magnetic field is applied normal to the disk surface. The new self-similar solution of the Navier-Stokes and energy equations is obtained numerically. The solution obtained here is not only the solution of the Navier-Stokes equations, but also of the boundary layer equations. Also, for a simple scaling factor, it represents the solution of the flow and heat transfer in the Forward Stagnation-Point region of a rotating sphere or over a rotating cone. The asymptotic behaviour of the solution for a large magnetic field or for a large independent variable is also examined. The surface shear stresses in the radial and tangential directions and the surface heat transfer increase as the acceleration parameter increases. Also the surface shear stress in the radial direction and the surface heat transfer decrease with increasing magnetic field, but the surface shear stress in the tangential direction increases. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved

  • Unsteady MHD flow and heat transfer on a rotating disk in an ambient fluid
    2002
    Co-Authors: Takhar H. S., Singh A. K., Nath G
    Abstract:

    An unsteady flow and heat transfer of a viscous incompressible electrically conducting fluid over a rotating infinite disk in an otherwise ambient fluid are studied. The unsteadiness in the flow field is caused by the angular velocity of the disk which varies with time. The magnetic field is applied normal to the disk surface. The new self-similar solution of the Navier-Stokes and energy equations is obtained numerically. The solution obtained here is not only the solution of the Navier-Stokes equations, but also of the boundary layer equations. Also, for a simple scaling factor, it represents the solution of the flow and heat transfer in the Forward Stagnation-Point region of a rotating sphere or over a rotating cone. The asymptotic behaviour of the solution for a large magnetic field or for a large independent variable is also examined. The surface shear stresses in the radial and tangential directions and the surface heat transfer increase as the acceleration parameter increases. Also the surface shear stress in the radial direction and the surface heat transfer decrease with increasing magnetic field, but the surface shear stress in the tangential direction increases

  • Self-similar solution of the unsteady flow in the Stagnation Point region of a rotating sphere with a magnetic field
    2000
    Co-Authors: Hs Takhar, Nath G
    Abstract:

    The unsteady flow and heat transfer of a viscous incompressible electrically conducting fluid in the Forward Stagnation Point region of a rotating sphere in the presence of a magnetic field are investigated in this study. The unsteadiness in the flow field is caused by the velocity at the edge of the boundary layer and the angular velocity of the rotating sphere, both varying continuously with time. The system of ordinary differential equations governing the flow is solved numerically. For some particular cases, an analytical solution is also obtained. It is found that the surface shear stresses in x- and y-directions and the surface heat transfer increase with the acceleration, the magnetic and the rotation parameters whether the magnetic field is fixed relative to the fluid or body, except that the surface shear stress in x-direction and the surface heat transfer decrease with increasing the magnetic parameter when the magnetic field is fixed relative to the body. For a certain value of the acceleration parameter, the surface shear stress in the x-direction vanishes while the surface shear stress in the y-direction and the surface heat transfer remain finite. Also, below a certain value of the acceleration parameter, reverse flow occurs in the x-component of the velocity profile

  • Development of Two-Dimensional Boundary Layer with an Applied Magnetic Field due to an Impulsive Motion
    1999
    Co-Authors: Kumari M, Nath G
    Abstract:

    The development of the asymmetric flow of a viscous electrically conducting fluid in the Forward Stagnation Point region of a two-dimensional body and over a stretching surface with an applied magnetic field has been investigated when the external stream or the stretching surface is set into an impulsive motion from rest. The analysis gives a uniformly valid solution starting from an initial time t=0 to the time t to infinity when the steady state is reached, the parabolic partial differential equations governing the unsteady flow have been solved numerically using an implicit finite-difference scheme. Analytical solutions have also been obtained for some particular cases. The surfaces shear stresses corresponding to symmetric and asymmetric flows increase with the magnetic field and tim

  • Unsteady compressible boundary layer flow in the Stagnation region of a sphere with a magnetic field
    1997
    Co-Authors: Hs Takhar, Yano K, Nakamura S, Nath G
    Abstract:

    Abstract: An analysis is performed to study the unsteady compressible laminar boundary layer flow in the Forward Stagnation-Point region of a sphere with a magnetic field applied normal, to the surface. We have considered the case where there is an initial steady state that is perturbed by the step change in the total enthalpy at the wall. The nonlinear coupled parabolic partial differential equations governing the flow and heat transfer have been solved numerically using a finite-difference scheme. The numerical results are presented, which show the temporal development of the boundary layer. The magnetic field in the presence of variable electrical conductivity causes an overshoot in the velocity profile. Also, when the total enthalpy at the wall is suddenly increased, there is a change in the direction of transfer of heat in a small interval of time

Roslinda Mohd Nazar - One of the best experts on this subject based on the ideXlab platform.

  • mhd flow of a nanofluid at the Forward Stagnation Point of an infinite permeable wall with a convective boundary condition
    2016
    Co-Authors: Siti Hidayah Muhad Saleh, Roslinda Mohd Nazar, Norihan Md Arifin, Ioan Pop
    Abstract:

    The steady magnetohydrodynamic (MHD) flow of a nanofluid at the Forward Stagnation Point of an infinite permeable wall is investigated in this study. A mathematical model has been constructed and the governing partial differential equations are converted into ordinary differential equations by similarity transformation. The similarity equations are solved numerically by a shooting technique. Results for the surface shear stresses, surface heat transfer, and velocity, nanoparticle fraction and temperature profiles are presented in tables and in some graphs. Effects of the magnetic parameter , constant mass flux Biot number , Brownion motion parameter thermophoresis parameter and Lewis number are examined. The present results are compared with previously available numerical results obtained using other methods of solution, and they are found to be in good agreement.

  • the development of forced convection heat transfer near a Forward Stagnation Point with newtonian heating
    2012
    Co-Authors: J H Merkin, Roslinda Mohd Nazar, Ioan Pop
    Abstract:

    A mathematical model for the unsteady forced convection boundary-layer flow near a Forward Stagnation Point is considered when there is Newtonian heating on the surface whereby the heat transfer is proportional to the local surface temperature. In a previous paper (Salleh et al. J Eng Math 69:101–110, 2011), a critical value γ c, dependent on the Prandtl number σ, of the heat transfer coefficient γ was identified, with solutions for the corresponding steady problem possible only for γ < γ c. The unsteady problem considered here shows that these steady states are attained at large times when γ < γ c. For γ > γ c, the solution still continues to large time, now growing exponentially with time. This rate of growth is determined by an eigenvalue problem which we solve numerically for general values of γ and σ and asymptotically for large γ and both large and small σ.

  • forced convection boundary layer flow at a Forward Stagnation Point with newtonian heating
    2009
    Co-Authors: Mohd Zuki Salleh, Roslinda Mohd Nazar, Ioan Pop
    Abstract:

    The steady forced convection boundary layer flow near the Forward Stagnation Point of an infinite plane wall generated by Newtonian heating in which the heat transfer from the surface is proportional to the local surface temperature is investigated in this study. The governing partial differential equations are first transformed into a system of ordinary differential equations before they are solved numerically by a finite-difference scheme, namely the Keller box method. Numerical solutions are obtained for a large range of values of the Prandtl number.

  • unsteady mixed convection near the Forward Stagnation Point of a two dimensional symmetric body prescribed with a constant wall heat flux
    2004
    Co-Authors: Roslinda Mohd Nazar, Ioan Pop
    Abstract:

    The unsteady mixed convection boundary layer flow near the Forward Stagnation Point of a two-dimensional symmetric body prescribed by a uniform heat flux rate is studied in this paper. The main aim of the investigation is to identify situations in which dual solutions for the steady-state flow can be determined when the flow is opposing. It is also shown that there is a smooth transition from the unsteady initial flow (short time) to the final steady state flow (large time).

  • Unsteady mixed convection near the Forward Stagnation Point of a two-dimensional symmetric body
    2003
    Co-Authors: Roslinda Mohd Nazar, Norsarahaida Amin
    Abstract:

    The unsteady mixed convection boundary layer flow near the Forward Stagnation Point of a two-dimensional symmetric body resulting from an impulsive motion of the free stream velocity and by sudden increase in the surface temperature. The partial differential equations governing the flow and heat transfer have been solved numerically using Keller-box method. It is shown that there is a smooth transition from the unsteady initial flow (short time) to the final steady state flow(large time). It is also found that for the steady flow case that are dual solutions when the flow is opposing

I Pop - One of the best experts on this subject based on the ideXlab platform.