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Anuar Mohd Ishak - One of the best experts on this subject based on the ideXlab platform.
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Unsteady Boundary layer flow of a nanofluid over a stretching shrinking sheet with a convective Boundary condition
Journal of the Egyptian Mathematical Society, 2016Co-Authors: Syahira Mansur, Anuar Mohd IshakAbstract:Abstract The Unsteady Boundary layer flow of a nanofluid past a stretching/shrinking sheet with a convective surface Boundary condition is studied. The effects of the unsteadiness parameter, stretching/shrinking parameter, convective parameter, Brownian motion parameter and thermophoresis parameter on the local Nusselt number are investigated. Numerical solutions to the governing equations are obtained using a shooting method. The results for the local Nusselt number are presented for different values of the governing parameters. The local Nusselt number decreases as the stretching/shrinking parameter increases. The local Nusselt number is consistently higher for higher values of the convective parameter but lower for higher values of the unsteadiness parameter, Brownian motion parameter and thermophoresis parameter.
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Unsteady Boundary layer flow of a nanofluid over a stretching/shrinking sheet with a convective Boundary condition
Journal of the Egyptian Mathematical Society, 2016Co-Authors: Syahira Mansur, Anuar Mohd IshakAbstract:Abstract The Unsteady Boundary layer flow of a nanofluid past a stretching/shrinking sheet with a convective surface Boundary condition is studied. The effects of the unsteadiness parameter, stretching/shrinking parameter, convective parameter, Brownian motion parameter and thermophoresis parameter on the local Nusselt number are investigated. Numerical solutions to the governing equations are obtained using a shooting method. The results for the local Nusselt number are presented for different values of the governing parameters. The local Nusselt number decreases as the stretching/shrinking parameter increases. The local Nusselt number is consistently higher for higher values of the convective parameter but lower for higher values of the unsteadiness parameter, Brownian motion parameter and thermophoresis parameter.
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Unsteady Boundary layer flow and heat transfer of a nanofluid over a permeable stretching shrinking sheet
International Journal of Heat and Mass Transfer, 2012Co-Authors: Norfifah Bachok, Anuar Mohd IshakAbstract:Abstract The Unsteady Boundary layer flow of a nanofluid over a permeable stretching/shrinking sheet is theoretically studied. The governing partial differential equations are transformed into ordinary ones using a similarity transformation, before being solved numerically. The results are obtained for the skin friction coefficient, the local Nusselt number and the local Sherwood number as well as the velocity, temperature and the nanoparticle fraction profiles for some values of the governing parameters, namely, the unsteadiness parameter, the mass suction parameter, the Brownian motion parameter, the thermophoresis parameter, Prandtl number, Lewis number and the stretching/shrinking parameter. It is found that dual solutions exist for both stretching and shrinking cases. The results also indicate that both unsteadiness and mass suction widen the range of the stretching/shrinking parameter for which the solution exists.
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Unsteady Boundary-layer flow and heat transfer of a nanofluid over a permeable stretching/shrinking sheet
International Journal of Heat and Mass Transfer, 2011Co-Authors: Norfifah Bachok, Anuar Mohd Ishak, I. PopAbstract:Abstract The Unsteady Boundary layer flow of a nanofluid over a permeable stretching/shrinking sheet is theoretically studied. The governing partial differential equations are transformed into ordinary ones using a similarity transformation, before being solved numerically. The results are obtained for the skin friction coefficient, the local Nusselt number and the local Sherwood number as well as the velocity, temperature and the nanoparticle fraction profiles for some values of the governing parameters, namely, the unsteadiness parameter, the mass suction parameter, the Brownian motion parameter, the thermophoresis parameter, Prandtl number, Lewis number and the stretching/shrinking parameter. It is found that dual solutions exist for both stretching and shrinking cases. The results also indicate that both unsteadiness and mass suction widen the range of the stretching/shrinking parameter for which the solution exists.
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Unsteady Boundary layer flow and heat transfer over a stretching surface in a micropolar fluid
2008Co-Authors: Roslinda Mohd. Nazar, Anuar Mohd Ishak, Maslina Darus, I. PopAbstract:The present study deals with the analysis of Unsteady Boundary layer flow and heat transfer of an incompressible micropolar fluid over a stretching sheet when the sheet is stretched in its own plane. The velocity and temperature are assumed to vary linearly with the distance along the sheet. Two equal and opposite forces are impulsively applied along the x-axis so that the sheet is stretched, keeping the origin fixed in a micropolar fluid. The transformed Unsteady Boundary layer equations are solved numerically using the Keller-box method for the whole transient from the initial state flow to the final steady-state flow. Numerical results are obtained for the velocity, microrotation and temperature distributions as well as the skin friction coefficient and local Nusselt number for various values of the material parameter K and Prandtl number Pr, when n= 1/2 (weak concentration particles at the plate).
Tiegang Fang - One of the best experts on this subject based on the ideXlab platform.
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New Unsteady Boundary layers over a long thin cylinder
Meccanica, 2015Co-Authors: Tiegang FangAbstract:In this paper, a new family of Unsteady Boundary layers over a long cylinder was investigated. This new class of Unsteady Boundary layers involves the flows over a long thin cylinder, whose leading end is either accretion or ablation at a certain rate. Using dimensionless variables, the governing partial differential equations are transformed into an ordinary differential equation, which was solved with a shooting method numerically. Under special cases, the solution can be solved explicitly. Solution domain was estimated and calculated numerically. It is found that a unique solution exists for accretion, while two solutions can exist for ablation. For other ablation parameters, there are no solutions. This new type of Unsteady Boundary layers over a cylinder enriches the literature on flow passing a cylinder and can provide benchmark problems for validating numerical code of computational fluid dynamics.
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A new family of Unsteady Boundary layers over a stretching surface
Applied Mathematics and Computation, 2010Co-Authors: Tiegang Fang, Ji Zhang, Shanshan YaoAbstract:Abstract In this paper, a new family of Unsteady Boundary layers over a stretching flat surface was proposed and studied. This new class of Unsteady Boundary layers involves the flows over a constant speed stretching surface from a slot, and the slot is moving at a certain speed. Depending on the slot moving parameter, the flow can be treated as a stretching sheet problem or a shrinking sheet problem. Both the momentum and thermal Boundary layers were studied. Under special conditions, the solutions reduce to the Unsteady Rayleigh problem and the steady Sakiadis stretching sheet problem. Solutions only exist for a certain range of the slot moving parameter, α. Two solutions are found for −53.55°
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A note on the Unsteady Boundary layers over a flat plate
International Journal of Non-Linear Mechanics, 2008Co-Authors: Tiegang FangAbstract:Abstract The Unsteady Boundary layer over a semi-infinite flat plate was investigated in this paper. The flow involves the Unsteady flow over a flat plate with leading edge accretion or ablation. The momentum Boundary layer was further analyzed and it was shown that the leading edge ablation had a similar effect to the wall mass injection or upstream wall movement making the fluid blown away from the wall. The thermal Boundary layer of the same flow was also studied. Results show that the leading edge accretion or ablation can greatly change the fluid motion and the heat transfer characteristics.
Krishnendu Bhattacharyya - One of the best experts on this subject based on the ideXlab platform.
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heat transfer analysis in Unsteady Boundary layer stagnation point flow towards a shrinking stretching sheet
Ain Shams Engineering Journal, 2013Co-Authors: Krishnendu BhattacharyyaAbstract:Abstract The heat transfer in Unsteady Boundary layer stagnation-point flow over a shrinking/stretching sheet is investigated. The surface temperature of the sheet is taken time dependent. The governing equations are transformed into self-similar ordinary differential equations by adopting similarity transformations and then the converted equations are solved numerically by shooting method. The study reveals that in addition to the velocity field, for the temperature distribution the dual solutions exist for some values of velocity ratio parameter. The heat transfer rate enhances due to the unsteadiness of the flow. The temperature for first solution decreases with unsteadiness parameter, and for second solution the temperature initially decreases, but it increases at large distance from the sheet. Moreover, for dual solutions as well as unique solution cases, the heat transfer rate increases with the Prandtl number in presence of unsteadiness.
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Slip Effects on an Unsteady Boundary Layer Stagnation-Point Flow and Heat Transfer towards a Stretching Sheet
Chinese Physics Letters, 2011Co-Authors: Krishnendu Bhattacharyya, Swati Mukhopadhyay, G.c. LayekAbstract:An analysis is presented for an Unsteady Boundary layer stagnation-point flow of a Newtonian fluid and the heat transfer towards a stretching sheet taking non-conventional partial slip conditions at the sheet. The self-similar equations are obtained using similarity transformations and solved numerically by the shooting method. Effects of the parameters involved in the equations, especially velocity slip and thermal slip parameters on the velocity and temperature profiles, are analyzed extensively. It is revealed that due to the velocity and thermal slip parameters, the rate of heat transfer from the sheet and the wall skin friction change significantly.
Meinhard T. Schobeiri - One of the best experts on this subject based on the ideXlab platform.
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Intermittency Based Unsteady Boundary Layer Transition Modeling: Implementation Into Navier-Stokes Equations
Volume 3: Turbo Expo 2005 Parts A and B, 2005Co-Authors: Meinhard T. SchobeiriAbstract:This paper presents recent advances in Boundary layer research that deal with an intermittency based Unsteady Boundary layer transition model and its implementation into the Reynolds averaged Navier-Stokes equations (RANS). RANS equations are conditioned to include the ensemble averaged Unsteady intermittency function. The Unsteady Boundary layer transition model is based on a universal Unsteady intermittency function developed earlier. It accounts for the effects of periodic Unsteady wake flow on the Boundary layer transition. The transition model is the result of an inductive approach analyzing the Unsteady data obtained by experiments on a curved plate at zero-streamwise pressure gradient under periodic Unsteady wake flow. To validate this model, systematic experimental investigations were conducted on the suction and pressure surfaces of turbine blades that were integrated into a turbine cascade test facility, which was designed for Unsteady Boundary layer investigations. This model is implemented into the above mentioned conditioned RANS-equations and calculation results are presented.© 2005 ASME
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Advances in Unsteady Boundary Layer Transition Research, Part II: Experimental Verification
International Journal of Rotating Machinery, 2003Co-Authors: Meinhard T. Schobeiri, L. WrightAbstract:This two-part article presents recent advances in Boundary layer research into the Unsteady Boundary layer transition modeling and its validation. This, Part II, deals with the results of an inductive approach based on comprehensive experimental and theoretical studies of Unsteady wake flow and Unsteady Boundary layer flow. The experiments were performed on a curved plate at a zero streamwise pressure gradient under periodic Unsteady wake flow, in which the frequency of the periodic Unsteady flow was varied. To validate the model, systematic experimental investigations were performed on the suction and pressure surfaces of turbine blades integrated into a high-subsonic cascade test facility, which was designed for Unsteady Boundary layer investigations. The analysis of the experiment’s results and comparison with the model’s prediction confirm the validity of the model and its ability to predict accurately the Unsteady Boundary layer transition.
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Advances in Unsteady Boundary Layer Transition Research, Part I: Theory and Modeling
International Journal of Rotating Machinery, 2003Co-Authors: Meinhard T. Schobeiri, L. WrightAbstract:This two-part article presents recent advances in Boundary layer research that deal with the Unsteady Boundary layer transition modeling and its validation. A new Unsteady Boundary layer transition model was developed based on a universal Unsteady intermittency function. It accounts for the effects of periodic Unsteady wake flow on the Boundary layer transition. To establish the transition model, an inductive approach was implemented; the approach was based on the results of comprehensive experimental and theoretical studies of Unsteady wake flow and Unsteady Boundary layer flow. The experiments were performed on a curved plate at a zero streamwise pressure gradient under a periodic Unsteady wake flow, where the frequency of the periodic Unsteady flow was varied. To validate the model, systematic experimental investigations were performed on the suction and pressure surfaces of turbine blades integrated into a high-subsonic cascade test facility, which was designed for Unsteady Boundary layer investigations. The analysis of the experiment's results and comparison with the model's prediction confirm the validity of the model and its ability to predict accurately the Unsteady Boundary layer transition.
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Prediction of turbine blade heat transfer and aerodynamics using a new Unsteady Boundary layer transition model
International Journal of Heat and Mass Transfer, 2002Co-Authors: Meinhard T. Schobeiri, P. ChakkaAbstract:Abstract The effects of periodic Unsteady flow on heat transfer and aerodynamic characteristics, particularly on the Boundary layer transition along the suction and the pressure surfaces of a typical gas turbine blade, are experimentally and theoretically investigated. Comprehensive aerodynamic and heat transfer experimental data are collected for different Unsteady passing frequencies that are typical of gas turbines. To predict the effect of the impinging periodic Unsteady flow on the heat transfer and the aerodynamics of turbine blades, a new Unsteady Boundary layer transition model is developed. The model is based on a universal Unsteady intermittency function and utilizes an inductive approach that implements the results of comprehensive experimental and theoretical studies of Unsteady wake development and the Boundary layer flow. Three distinct quantities are identified as primarily responsible for the transition of an Unsteady Boundary layer: (1) the universal relative intermittency function, (2) maximum intermittency, and (3) minimum intermittency. The analysis of the experimental results and the comparison with the model prediction confirm the validity of the model and its capability to accurately predict the Unsteady Boundary layer transition.
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Modeling Unsteady Boundary Layer Transition on a Curved Plate Under Periodic Unsteady Flow Conditions: Aerodynamic and Heat Transfer Investigations
Journal of Turbomachinery, 1999Co-Authors: P. Chakka, Meinhard T. SchobeiriAbstract:A Boundary layer transition model is developed that accounts for the effects of periodic Unsteady wake flow on the Boundary layer transition. To establish the model, comprehensive Unsteady Boundary layer and heat transfer experimental investigations are conducted. The experiments are performed on a curved plate at zero-streamwise pressure gradient under periodic Unsteady wake flow, where the frequency of the periodic Unsteady flow is varied. The analysis of the time-dependent velocities, turbulence intensities, and turbulence intermittencies has identified three distinct quantities as primarily responsible for the transition of an Unsteady Boundary layer. These quantities, which exhibit the basis of the transition model presented in this paper, are: (1) relative intermittency, (2) maximum intermittency, and (3) minimum intermittency. To validate the developed transition model, it is implemented in an existing Boundary layer code, and the resulting velocity profiles and the heat transfer coefficients are compared with the experimental data.
I. Pop - One of the best experts on this subject based on the ideXlab platform.
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Unsteady Boundary-layer flow and heat transfer of a nanofluid over a permeable stretching/shrinking sheet
International Journal of Heat and Mass Transfer, 2011Co-Authors: Norfifah Bachok, Anuar Mohd Ishak, I. PopAbstract:Abstract The Unsteady Boundary layer flow of a nanofluid over a permeable stretching/shrinking sheet is theoretically studied. The governing partial differential equations are transformed into ordinary ones using a similarity transformation, before being solved numerically. The results are obtained for the skin friction coefficient, the local Nusselt number and the local Sherwood number as well as the velocity, temperature and the nanoparticle fraction profiles for some values of the governing parameters, namely, the unsteadiness parameter, the mass suction parameter, the Brownian motion parameter, the thermophoresis parameter, Prandtl number, Lewis number and the stretching/shrinking parameter. It is found that dual solutions exist for both stretching and shrinking cases. The results also indicate that both unsteadiness and mass suction widen the range of the stretching/shrinking parameter for which the solution exists.
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Unsteady Boundary layer flow induced by accelerating motion near the rear stagnation point in a micropolar fluid
International Journal of Fluid Mechanics Research, 2009Co-Authors: Yian Yian Lok, Norsarahaida Amin, I. PopAbstract:The Unsteady Boundary layer flow of a micropolar fluid induced by a two-dimensional body, which is started impulsively from rest, is studied in this paper. The variation with time t of the external stream V(t) is assumed to be of the form V(t) 1 - exp(-atm), where a = 0 means a coefficient of acceleration and m is an arbitrary integral value. The problem is formulated for the flow at the rear stagnation point on an infinite plane wall. Numerical solutions of the Unsteady Boundary layer equations are obtained using an implicit finite-difference scheme known as the Keller's box method. Results are given for the velocity and microrotation profiles, as well as for the dimensionless time elapsed before the Boundary layer begins to separate from the wall. It is found that the dimensionless time elapsed before separation takes place is lower for a micropolar fluid (K 0) than for a Newtonian fluid (K 0), where K denotes the micropolar or material parameter.
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Unsteady Boundary layer flow and heat transfer over a stretching surface in a micropolar fluid
2008Co-Authors: Roslinda Mohd. Nazar, Anuar Mohd Ishak, Maslina Darus, I. PopAbstract:The present study deals with the analysis of Unsteady Boundary layer flow and heat transfer of an incompressible micropolar fluid over a stretching sheet when the sheet is stretched in its own plane. The velocity and temperature are assumed to vary linearly with the distance along the sheet. Two equal and opposite forces are impulsively applied along the x-axis so that the sheet is stretched, keeping the origin fixed in a micropolar fluid. The transformed Unsteady Boundary layer equations are solved numerically using the Keller-box method for the whole transient from the initial state flow to the final steady-state flow. Numerical results are obtained for the velocity, microrotation and temperature distributions as well as the skin friction coefficient and local Nusselt number for various values of the material parameter K and Prandtl number Pr, when n= 1/2 (weak concentration particles at the plate).
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Similiarity solutions for the Unsteady Boundary layer flow and heat transfer due to a stretching sheet
International Journal of Applied Mechanics and Engineering, 2006Co-Authors: S. Sharidan, T. Mahmood, I. PopAbstract:A similarity analysis is presented to investigate the Unsteady Boundary layers over a stretching sheet for special distributions of the stretching velocity and surface temperature or surface heat flux. The governing Unsteady Boundary layer equations are reduced to ordinary differential equations with two parameters, the Prandtl number and the unsteadiness parameter. These equations are solved numerically for some values of the governing parameters using the Keller-box method. Some flow and heat transfer characteristics are determined and discussed in detail.
