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Ioan Pop - One of the best experts on this subject based on the ideXlab platform.
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hybrid nanofluid flow and heat transfer over a nonlinear permeable stretching shrinking surface
International Journal of Numerical Methods for Heat & Fluid Flow, 2019Co-Authors: Iskandar Waini, Anuar Mohd Ishak, Ioan PopAbstract:This paper aims to investigate the steady flow and heat transfer of a Cu-Al2O3/water hybrid nanofluid over a nonlinear permeable stretching/shrinking surface with radiation effects. The surface velocity condition is assumed to be of the power-law form with an exponent of 1/3. The governing equations of the problem are converted into a system of similarity equations by using a similarity transformation.,The problem is solved numerically using the boundary value problem solver (bvp4c) in Matlab software. The results of the skin friction Coefficient and the local Nusselt number as well as the velocity and temperature profiles are presented through graphs and tables for several values of the parameters. The effects of these parameters on the flow and heat transfer characteristics are examined and discussed.,Results found that dual solutions exist for a certain range of the stretching/shrinking and suction parameters. The increment of the skin friction Coefficient and reduction of the local Nusselt number on the shrinking sheet is observed with the increasing of copper (Cu) nanoparticle volume fractions for the upper branch. The skin friction Coefficient and the local Nusselt number increase when suction parameter is increased for the upper branch. Meanwhile, the temperature increases in the presence of the radiation parameter for both branches.,The problem of Cu-Al2O3/water hybrid nanofluid flow and heat transfer over a nonlinear permeable stretching/shrinking surface with radiation effects is the important originality of the present study where the dual solutions for the flow reversals are obtained.
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tiwari das nanofluid model for magnetohydrodynamics mhd natural convective flow of a nanofluid adjacent to a spinning down pointing vertical cone
Propulsion and Power Research, 2018Co-Authors: Mohammad Aghamajidi, Mohammad Eftekhari Yazdi, Saeed Dinarvand, Ioan PopAbstract:Abstract In this article, the natural-convective flow of an electrically conducting nanofluid adjacent to a spinning down-pointing vertical cone in the presence of transverse magnetic field is studied. The mathematical model has been formulated based on Tiwari-Das nanofluid model. Three different types of water-based nanofluid with copper, aluminum oxide (alumina) and titanium dioxide (titania) as nanoparticles are considered in this investigation. Two cases of heat transfer analysis are discussed. These are: (i) the spinning cone with prescribed surface temperature and (ii) the spinning cone with prescribed surface heat flux. Using appropriate transformations, the system of partial differential equations is transformed into an ordinary differential system of three equations, which is solved numerically using the fourth-order Runge-Kutta method with shooting technique. The current solution demonstrates very good agreement with those of the previously published studies in the especial cases. The effects of the three key thermophysical parameters governing the flow; the nanoparticle volume fraction, the magnetic parameter and the spin parameter on dimensionless velocity and temperature distributions, skin friction Coefficient, Nusselt number and entropy generation number are presented graphically and discussed in details. Our results demonstrate that, the enhancement of heat transfer is a function of particle concentration, small fraction of metallic particles leading to significant changes in all three quantities of skin friction Coefficient, local Nusselt number and entropy generation number. The results illustrate that selecting alumina and copper as the nanoparticle leads to the minimum and maximum amounts of skin friction Coefficient value, and also copper and titania nanoparticles have the largest and lowest local Nusselt number. Moreover, it is observed that the magnetic parameter has a decreasing effect on both skin friction Coefficient and local Nusselt number and an increasing effect on entropy generation number. In addition, our computation shows that all three quantities of skin friction Coefficient, local Nusselt number and entropy generation number are the increasing functions of spin parameter. Finally, this simulation represents the feasibility of using magnetic rotating body drives in novel nuclear space propulsion engines and this model has important applications in heat transfer enhancement in renewable energy systems and industrial thermal management.
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axisymmetric mixed convective stagnation point flow of a nanofluid over a vertical permeable cylinder by tiwari das nanofluid model
Powder Technology, 2017Co-Authors: Saeed Dinarvand, Reza Hosseini, Ioan PopAbstract:Abstract In this article, the steady axisymmetric mixed convective stagnation-point flow of an incompressible electrically conducting nanofluid over a vertical permeable circular cylinder in the presence of transverse magnetic field is investigated. The mathematical model has been formulated based on Tiwari-Das nanofluid model. In this study, the water as the base fluid and three different types of nanoparticles; copper, aluminum oxide (alumina) and titanium dioxide (titania) are considered. Using appropriate transformations, the system of partial differential equations is transformed into an ordinary differential system of two equations, which is solved analytically by the well-known homotopy analysis method (HAM) and numerically using the fourth-order Runge–Kutta method with shooting technique. The present analytical and numerical simulations agree closely with the previous studies in the especial cases. The effects of the five key thermophysical parameters governing the flow; the nanoparticle volume fraction (ϕ), the magnetic parameter (M), the wall permeability parameter (Vw), the mixed convection parameter (λ) and the curvature parameter (γ) on dimensionless velocity and temperature distributions, skin friction Coefficient and local Nusselt number are presented graphically and discussed in details. Our results demonstrate that, the enhancement of heat transfer is a function of particle concentration, small fraction of metallic particles leading to significant changes in both skin friction Coefficient and local Nusselt number. The results illustrate that selecting alumina and copper as the nanoparticle leads to the minimum and maximum amounts of skin friction Coefficient value, and also copper and titania nanoparticles have the largest and lowest local Nusselt number. In addition, our computation shows that the curvature parameter has a strong additive effect on the skin friction Coefficient and local Nusselt number. Moreover, it is observed that the highest velocity and thermal boundary layer thickness are related to the opposing flow, while the smallest one is for assisting flow.
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boundary layer flow and heat transfer past a permeable shrinking surface embedded in a porous medium with a second order slip a stability analysis
Applied Thermal Engineering, 2017Co-Authors: Mohd Hafizi Mat Yasin, Anuar Mohd Ishak, Ioan PopAbstract:Abstract The fluid flow and heat transfer over a permeable shrinking sheet embedded in a porous medium with a second-order slip is studied. Using appropriate similarity variables, the governing partial differential equations are reduced to ordinary differential equations before being solved numerically by a shooting method for different values of the selected governing parameters. The numerical results reveal that two (dual) solutions are possible for a certain range of these parameters. A stability analysis is performed to determine which solution is stable and which one is not. The effects of suction and the second order slip parameters on the skin friction Coefficient and the local Nusselt number as well as on the velocity and temperature profiles are plotted and discussed. It is found that applying the slip condition increases the range of solutions. Also, the skin friction Coefficient is higher for the no slip condition compared to that of with slip condition.
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semi analytical solution for the flow of a nanofluid over a permeable stretching shrinking sheet with velocity slip using buongiorno s mathematical model
European Journal of Mechanics B-fluids, 2016Co-Authors: Natalia C Rosca, Alin V Rosca, Emad H Aly, Ioan PopAbstract:Abstract In this analysis, the flow and heat transfer characteristics of a nanofluid over a stretching/shrinking surface with suction are investigated. Using a similarity transformation, the nonlinear system of partial differential equations is converted into nonlinear ordinary differential equations. These resulting equations are solved analytically and numerically using a collocation method. Multiple (dual: upper and lower branch) solutions are shown to exist in a range of the governing parameters. In addition, the reduced skin friction Coefficient and the reduced heat transfer from the surface of the sheet as well as the velocity, temperature and concentration profiles are analyzed subject to several parameters of interest, namely suction parameter, Brownian motion and thermophoresis parameters, Prandtl number, nanofluid Lewis number and dimensionless slip parameter. The results indicate that the skin friction Coefficient and the heat transfer from the surface of the sheet increase with suction effect. It is also observed that suction widens the range of the stretching/shrinking parameter for which the solution exists.
Tasawar Hayat - One of the best experts on this subject based on the ideXlab platform.
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darcy forchheimer flow due to a curved stretching surface with cattaneo christov double diffusion a numerical study
Results in physics, 2017Co-Authors: Taseer Muhammad, Tasawar Hayat, Farwa Haider, Ahmed AlsaediAbstract:Abstract This communication addresses the Darcy-Forchheimer flow by an unsteady curved stretching surface. Flow in porous medium is characterized by Darcy-Forchheimer relation. Cattaneo-Christov double diffusion expressions are implemented in modelling. Suitable transformations correspond to a strong nonlinear ordinary differential problems. The problems are numerically solved. Outcomes of emerging flow variables on velocity, temperature and concentration fields are plotted. Skin friction Coefficient and local Nusselt and Sherwood numbers are computed and examined. Our findings reveal that the skin friction Coefficient is an increasing function of Forchheimer number.
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Impacts of constructive and destructive chemical reactions in magnetohydrodynamic (MHD) flow of Jeffrey liquid due to nonlinear radially stretched surface
Journal of Molecular Liquids, 2017Co-Authors: Tasawar Hayat, Muhammad Waqas, M. Ijaz Khan, Ahmed AlsaediAbstract:Abstract This investigation examines the effects of chemical reaction in the two-dimensional flow of Jeffrey liquid due to nonlinear radially stretched surface. The flow analysis is conducted under the action of applied magnetic field. Heat transfer is considered in the presence of Joule heating, heat generation/absorption and Newtonian heating. Convergent solutions to the nonlinear formulation are developed. Skin friction Coefficient, local Nusselt and Sherwood numbers are tabulated and addressed for the various embedded parameters. It is anticipated that concentration distribution enhances via larger destructive chemical reaction parameter and reduces when generative chemical reaction parameter is enhanced. Furthermore the temperature decays for increasing nonlinear parameter of axisymmetric stretching surface. The nonlinear parameter has reverse effect for temperature and skin friction Coefficient.
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comparative study of silver and copper water nanofluids with mixed convection and nonlinear thermal radiation
International Journal of Heat and Mass Transfer, 2016Co-Authors: Maria Imtiaz, Tasawar Hayat, Sumaira Qayyum, Ahmed AlsaediAbstract:Abstract This article analyzes the mixed convection flow of magnetohydrodynamic (MHD) nanofluid. Water based nanofluid comprising silver and copper as nanoparticles is used. Fluid fills the porous space. Heat transfer analysis is carried out in the presence of nonlinear thermal radiation. Ordinary differential equations are formed by using suitable transformations. Convergent series solutions are obtained. Influence of involved parameters on velocity and temperature are analyzed graphically. Calculations for skin friction Coefficient and Nusselt number are evaluated and examined for the pertinent parameters. It is observed that velocity profiles for both nanofluids show decreasing behavior for Hartman number and angle of inclination. Temperature profile enhances for increasing temperature ratio parameter and radiation parameter in copper water nanofluid. Skin friction Coefficient and Nusselt number are increasing functions of mixed convection parameter. However the effects of silver nanofluid dominant for skin friction while copper nanofluid dominant over silver nanofluid for local Nusselt number.
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effects of homogeneous heterogeneous reactions in flow of magnetite fe3o4 nanoparticles by a rotating disk
Journal of Molecular Liquids, 2016Co-Authors: Ahmed Alsaedi, Tasawar Hayat, Maria Imtiaz, Faris AlzahraniAbstract:This article addresses the flow of ferrofluid due to a rotating disk in the presence of homogeneous–heterogeneous reactions. The disk rotates with constant angular velocity about the z-axis. Water is used as base fluid while magnetite-Fe3 O4 as nanoparticle. Fluid is electrically conducting in the presence of an applied magnetic field. Effects of viscous dissipation are also considered. The disk is kept at uniform temperature while there is ambient temperature away from the disk. In view of the rotational symmetry, the derivatives in the azimuthal direction are neglected. Appropriate transformations reduce the system of nonlinear partial differential equations to system of ordinary differential equations. Convergent series solutions are computed using homotopy analysis method (HAM) for the resulting nonlinear problems. Effects of different parameters on the velocity, temperature and concentration profiles are shown and analyzed. Computations for skin friction Coefficient and Nusselt number are presented and examined for the influences of pertinent parameters. It is noted that concentration distribution decreases for larger values of strength of homogeneous reaction parameter while it increases for strength of heterogeneous reaction parameter. Skin friction Coefficient and rate of heat transfer are enhanced when the strength of magnetic field is increased.
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effect of joule heating and thermal radiation in flow of third grade fluid over radiative surface
PLOS ONE, 2014Co-Authors: Tasawar Hayat, Anum Shafiq, Ahmed AlsaediAbstract:This article addresses the boundary layer flow and heat transfer in third grade fluid over an unsteady permeable stretching sheet. The transverse magnetic and electric fields in the momentum equations are considered. Thermal boundary layer equation includes both viscous and Ohmic dissipations. The related nonlinear partial differential system is reduced first into ordinary differential system and then solved for the series solutions. The dependence of velocity and temperature profiles on the various parameters are shown and discussed by sketching graphs. Expressions of skin friction Coefficient and local Nusselt number are calculated and analyzed. Numerical values of skin friction Coefficient and Nusselt number are tabulated and examined. It is observed that both velocity and temperature increases in presence of electric field. Further the temperature is increased due to the radiation parameter. Thermal boundary layer thickness increases by increasing Eckert number.
Ahmed Alsaedi - One of the best experts on this subject based on the ideXlab platform.
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axisymmetric flow by a rotating disk with cattaneo christov heat flux
Journal of The Brazilian Society of Mechanical Sciences and Engineering, 2019Co-Authors: Maria Imtiaz, Asmara Kiran, Ahmed AlsaediAbstract:Here, axisymmetric flow of Jeffrey fluid by a rotating disk with variable thicked surface is studied. Heat transfer is discussed through Cattaneo–Christov heat flux model. Transformation procedure has been adopted in obtaining ordinary differential systems. Convergent series solutions are obtained. Flow, temperature and skin friction Coefficient for various parameters of interest are graphically illustrated. The radial and tangential velocities are increasing functions of Deborah number.
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Darcy-Forchheimer flows of copper and silver water nanofluids between two rotating stretchable disks
Applied Mathematics and Mechanics, 2017Co-Authors: T. Hayat, H. Nazar, M. Imtiaz, Ahmed AlsaediAbstract:This investigation describes the nanofluid flow in a non-Darcy porous medium between two stretching and rotating disks. A nanofluid comprises of nanoparticles of silver and copper. Water is used as a base fluid. Heat is being transferred with thermal radiation and the Joule heating. A system of ordinary differential equations is obtained by appropriate transformations. Convergent series solutions are obtained. Effects of various parameters are analyzed for the velocity and temperature. Numerical values of the skin friction Coefficient and the Nusselt number are tabulated and examined. It can be seen that the radial velocity is affected in the same manner with both porous and local inertial parameters. A skin friction Coefficient depicts the same impact on both disks for both nanofluids with larger stretching parameters.
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darcy forchheimer flow due to a curved stretching surface with cattaneo christov double diffusion a numerical study
Results in physics, 2017Co-Authors: Taseer Muhammad, Tasawar Hayat, Farwa Haider, Ahmed AlsaediAbstract:Abstract This communication addresses the Darcy-Forchheimer flow by an unsteady curved stretching surface. Flow in porous medium is characterized by Darcy-Forchheimer relation. Cattaneo-Christov double diffusion expressions are implemented in modelling. Suitable transformations correspond to a strong nonlinear ordinary differential problems. The problems are numerically solved. Outcomes of emerging flow variables on velocity, temperature and concentration fields are plotted. Skin friction Coefficient and local Nusselt and Sherwood numbers are computed and examined. Our findings reveal that the skin friction Coefficient is an increasing function of Forchheimer number.
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Impacts of constructive and destructive chemical reactions in magnetohydrodynamic (MHD) flow of Jeffrey liquid due to nonlinear radially stretched surface
Journal of Molecular Liquids, 2017Co-Authors: Tasawar Hayat, Muhammad Waqas, M. Ijaz Khan, Ahmed AlsaediAbstract:Abstract This investigation examines the effects of chemical reaction in the two-dimensional flow of Jeffrey liquid due to nonlinear radially stretched surface. The flow analysis is conducted under the action of applied magnetic field. Heat transfer is considered in the presence of Joule heating, heat generation/absorption and Newtonian heating. Convergent solutions to the nonlinear formulation are developed. Skin friction Coefficient, local Nusselt and Sherwood numbers are tabulated and addressed for the various embedded parameters. It is anticipated that concentration distribution enhances via larger destructive chemical reaction parameter and reduces when generative chemical reaction parameter is enhanced. Furthermore the temperature decays for increasing nonlinear parameter of axisymmetric stretching surface. The nonlinear parameter has reverse effect for temperature and skin friction Coefficient.
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comparative study of silver and copper water nanofluids with mixed convection and nonlinear thermal radiation
International Journal of Heat and Mass Transfer, 2016Co-Authors: Maria Imtiaz, Tasawar Hayat, Sumaira Qayyum, Ahmed AlsaediAbstract:Abstract This article analyzes the mixed convection flow of magnetohydrodynamic (MHD) nanofluid. Water based nanofluid comprising silver and copper as nanoparticles is used. Fluid fills the porous space. Heat transfer analysis is carried out in the presence of nonlinear thermal radiation. Ordinary differential equations are formed by using suitable transformations. Convergent series solutions are obtained. Influence of involved parameters on velocity and temperature are analyzed graphically. Calculations for skin friction Coefficient and Nusselt number are evaluated and examined for the pertinent parameters. It is observed that velocity profiles for both nanofluids show decreasing behavior for Hartman number and angle of inclination. Temperature profile enhances for increasing temperature ratio parameter and radiation parameter in copper water nanofluid. Skin friction Coefficient and Nusselt number are increasing functions of mixed convection parameter. However the effects of silver nanofluid dominant for skin friction while copper nanofluid dominant over silver nanofluid for local Nusselt number.
Anuar Mohd Ishak - One of the best experts on this subject based on the ideXlab platform.
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hybrid nanofluid flow and heat transfer over a nonlinear permeable stretching shrinking surface
International Journal of Numerical Methods for Heat & Fluid Flow, 2019Co-Authors: Iskandar Waini, Anuar Mohd Ishak, Ioan PopAbstract:This paper aims to investigate the steady flow and heat transfer of a Cu-Al2O3/water hybrid nanofluid over a nonlinear permeable stretching/shrinking surface with radiation effects. The surface velocity condition is assumed to be of the power-law form with an exponent of 1/3. The governing equations of the problem are converted into a system of similarity equations by using a similarity transformation.,The problem is solved numerically using the boundary value problem solver (bvp4c) in Matlab software. The results of the skin friction Coefficient and the local Nusselt number as well as the velocity and temperature profiles are presented through graphs and tables for several values of the parameters. The effects of these parameters on the flow and heat transfer characteristics are examined and discussed.,Results found that dual solutions exist for a certain range of the stretching/shrinking and suction parameters. The increment of the skin friction Coefficient and reduction of the local Nusselt number on the shrinking sheet is observed with the increasing of copper (Cu) nanoparticle volume fractions for the upper branch. The skin friction Coefficient and the local Nusselt number increase when suction parameter is increased for the upper branch. Meanwhile, the temperature increases in the presence of the radiation parameter for both branches.,The problem of Cu-Al2O3/water hybrid nanofluid flow and heat transfer over a nonlinear permeable stretching/shrinking surface with radiation effects is the important originality of the present study where the dual solutions for the flow reversals are obtained.
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unsteady mhd flow and heat transfer over a shrinking sheet with ohmic heating
Chinese Journal of Physics, 2017Co-Authors: Siti Khuzaimah Soid, Anuar Mohd IshakAbstract:Abstract The problem of unsteady magnetohydrodynamic (MHD) stagnation point flow over a stretching/shrinking sheet in a viscous fluid with viscous dissipation and ohmic heating is studied in this paper. The physical problem is modeled using a system of nonlinear partial differential equations and are then transformed into ordinary (similarity) differential equations using a proper transformation. These equations along with the corresponding boundary conditions are solved numerically using bvp4c in Matlab software. The solution is found to be dependent on the governing parameters including the magnetic field parameter, the Eckert number, unsteadiness parameter and the Prandtl number. The results illustrated include the velocity and temperature profiles, as well as local Skin-Friction Coefficient and the local Nusselt number. It is found that dual (first and second) solutions exist only for the shrinking sheet case. It is also observed that the magnetic and unsteadiness parameters give prominent effects on the fluid flow and heat transfer. These two parameters cause a rise in the skin friction Coefficient and the rate of heat transfer.
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boundary layer flow and heat transfer past a permeable shrinking surface embedded in a porous medium with a second order slip a stability analysis
Applied Thermal Engineering, 2017Co-Authors: Mohd Hafizi Mat Yasin, Anuar Mohd Ishak, Ioan PopAbstract:Abstract The fluid flow and heat transfer over a permeable shrinking sheet embedded in a porous medium with a second-order slip is studied. Using appropriate similarity variables, the governing partial differential equations are reduced to ordinary differential equations before being solved numerically by a shooting method for different values of the selected governing parameters. The numerical results reveal that two (dual) solutions are possible for a certain range of these parameters. A stability analysis is performed to determine which solution is stable and which one is not. The effects of suction and the second order slip parameters on the skin friction Coefficient and the local Nusselt number as well as on the velocity and temperature profiles are plotted and discussed. It is found that applying the slip condition increases the range of solutions. Also, the skin friction Coefficient is higher for the no slip condition compared to that of with slip condition.
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mhd heat and mass transfer flow over a permeable stretching shrinking sheet with radiation effect
Journal of Magnetism and Magnetic Materials, 2016Co-Authors: Mohd Hafizi Mat Yasin, Anuar Mohd IshakAbstract:Abstract The steady two-dimensional magnetohydrodynamic (MHD) flow past a permeable stretching/shrinking sheet with radiation effects is investigated. The similarity transformation is introduced to transform the governing partial differential equations into a system of ordinary differential equations before being solved numerically using a shooting method. 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 concentration profiles for some values of the governing parameters, namely, suction/injection parameter S , stretching/shrinking parameter λ , magnetic parameter M , radiation parameter R , heat source/sink Q and chemical rate parameter K. For the shrinking case, there exist two solutions for a certain range of parameters, but the solution is unique for the stretching case. The stability analysis verified that the upper branch solution is linearly stable and physically reliable while the lower branch solution is not. For the reliable solution, the skin friction Coefficient increases in the present of magnetic field. The heat transfer rate at the surface decreases in the present of radiation.
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stagnation point flow and heat transfer over a stretching shrinking sheet in a viscoelastic fluid with convective boundary condition and partial slip velocity
European Physical Journal Plus, 2015Co-Authors: Muhammad Khairul Anuar Mohamed, Anuar Mohd Ishak, Mohdi Zuki Salleh, Ioan PopAbstract:In this study, the mathematical modeling for the stagnation point flow and heat transfer over a stretching/shrinking surface in a viscoelastic fluid (Walter’s liquid-B model) with partial slip velocity is considered. The non-linear partial differential equations are transformed into a system of ordinary differential equations by a similarity transformation before being solved numerically using the Runge-Kutta-Fehlberg method. Numerical solutions are obtained for the surface temperature, temperature gradient at the surface and the skin friction Coefficient. The features of the flow and heat transfer characteristics for various values of Prandtl number, the dimensionless viscoelastic parameter, stretching parameter, constant velocity slip parameter and conjugate parameter are analyzed and discussed. It is found that the heat transfer rate is higher for Walter’s fluid compared to the classical viscous fluid and the presence of the velocity slip reduces the effects of the viscoelastic parameter on the skin friction Coefficient.
Tamer A Zaki - One of the best experts on this subject based on the ideXlab platform.
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turbulence and skin friction modification in channel flow with streamwise aligned superhydrophobic surface texture
Physics of Fluids, 2014Co-Authors: Thomas Jelly, Seo Yoon Jung, Tamer A ZakiAbstract:Direct numerical simulations of turbulent flow in a channel with superhydrophobic surfaces (SHS) were performed, and the effects of the surface texture on the turbulence and Skin-Friction Coefficient were examined. The SHS is modeled as a planar boundary comprised of spanwise-alternating regions of no-slip and free-slip boundary conditions. Relative to the reference no-slip channel flow at the same bulk Reynolds number, the overall mean Skin-Friction Coefficient is reduced by 21.6%. A detailed analysis of the turbulence kinetic energy budget demonstrates a reduction in production over the no-slip phases, which is explained by aid of quadrant analysis of the Reynolds shear stresses and statistical analysis of the turbulence structures. The results demonstrate a significant reduction in the strength of streamwise vortical structures in the presence of the SHS texture and a decrease in the Reynolds shear-stress component ⟨R12⟩ which has a favorable influence on drag over the no-slip phases. A secondary flow ...
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turbulence and skin friction modification in channel flow with streamwise aligned superhydrophobic surface texture
Physics of Fluids, 2014Co-Authors: Thomas Jelly, Seo Yoon Jung, Tamer A ZakiAbstract:Direct numerical simulations of turbulent flow in a channel with superhydrophobic surfaces (SHS) were performed, and the effects of the surface texture on the turbulence and Skin-Friction Coefficient were examined. The SHS is modeled as a planar boundary comprised of spanwise-alternating regions of no-slip and free-slip boundary conditions. Relative to the reference no-slip channel flow at the same bulk Reynolds number, the overall mean Skin-Friction Coefficient is reduced by 21.6%. A detailed analysis of the turbulence kinetic energy budget demonstrates a reduction in production over the no-slip phases, which is explained by aid of quadrant analysis of the Reynolds shear stresses and statistical analysis of the turbulence structures. The results demonstrate a significant reduction in the strength of streamwise vortical structures in the presence of the SHS texture and a decrease in the Reynolds shear-stress component ⟨R 12⟩ which has a favorable influence on drag over the no-slip phases. A secondary flow which is set up at the edges of the texture also effects a beneficial change in drag. Nonetheless, the Skin-Friction Coefficient on the no-slip features is higher than the reference levels in a simple no-slip channel flow. The increase in the Skin-Friction Coefficient is attributed to two factors. First, spanwise diffusion of the mean momentum from free-slip to no-slip regions increases the local Skin-Friction Coefficient on the edges of the no-slip features. Second, the drag-reducing capacity of the SHS is further reduced due to additional Reynolds stresses, ⟨R 13⟩.
