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1.
Sufficient conditions are found for the existence of similar solutions of the mixed convection flow of a Powell-Eyring fluid over a nonlinear stretching permeable sur- face in the presence of magnetic field. To achieve this, one parameter linear group trans- formation is applied. The governing momentum and energy equations are transformed to nonlinear ordinary differential equations by use of a similarity transformation. These equations are solved by the homotopy analysis method (HAM) to obtain the approximate solutions. The effects of magnetic field, suction, and buoyancy on the Powell-Eyring fluid flow with heat transfer inside the boundary layer are analyzed. The effects of the non- Newtonian fluid (Powell-Eyring model) parameters ε and δon the skin friction and local heat transfer coefficients for the cases of aiding and opposite flows are investigated and discussed. It is observed that the momentum boundary layer thickness increases and the thermal boundary layer thickness decreases with the increase in ε whereas the momentum boundary layer thickness decreases and thermal boundary layer thickness increases with the increase in δ for both the aiding and opposing mixed convection flows. 相似文献
2.
Heat transfer characteristics of a non-Newtonian fluid on a power-law stretched surface of variable temperature with suction
or injection were investigated. Similarity solutions of the laminar boundary layer equations describing heat transfer and
fluid flow in a quiescent fluid were obtained and solved numerically. Velocity and temperature profiles as well as the Nusselt
number, Nu, were studied for two thermal boundary conditions; uniform surface temperature and variable surface temperature,
for different parameters; Prandtl number Pr, temperature exponent b, velocity exponent m, injection parameter d and power-law index n. It was found that decreasing injection parameter d, and power-law index n and increasing Prandtl number Pr and surface temperature exponent b enhance the heat transfer coefficient.
Received on 27 April 2000 相似文献
3.
Heat transfer characteristics in the laminar boundary layer with transpiration cooling function are numerically analyzed by
an integral method. The effects of coolant injection ratio, and the Re and Pr numbers of the exterior hot flow on the temperature at porous plate surface are discussed. The numerical results and discussions
indicate that the surface temperature falls with an increase of coolant injection ratio, the temperature distribution on the
surface is not uniform, and the effects of the Re number under lower Pr number condition are distinctly different to that under the higher Pr number condition. 相似文献
4.
The influence of third grade, partial slip and other thermophysical parameters on the steady flow, heat and mass transfer of viscoelastic third grade fluid past an infinite vertical insulated plate subject to suction across the boundary layer has been investigated. The space occupying the fluid is porous. The momentum equation is characterized by a highly nonlinear boundary value problem in which the order of the differential equation exceeds the number of available boundary conditions. An efficient numerical scheme of midpoint technique with Richardson’s extrapolation is employed to solve the governing system of coupled nonlinear equations of momentum, energy and concentration. Numerical calculations were carried out for different values of various interesting non-dimensional quantities in the slip flow regime with heat and mass transfer and were shown with the aid of figures. The values of the wall shear stress, the local rate of heat and mass transfers were obtained and tabulated. The analysis shows that as the fluid becomes more shear thickening, the momentum boundary layer decreases but the thermal boundary layer increases; the magnetic field strength is found to decrease with an increasing temperature distribution when the porous plate is insulated. The consequences of increasing the permeability parameter and Schmidt number decrease both the momentum and concentration boundary layer thicknesses respectively whereas an increase in the thermal Grashof number gives rise to the thermal boundary layer thickness. 相似文献
5.
In this paper, the problem of free convection boundary layer flow on a solid sphere in a micropolar fluid with Newtonian heating,
in which the heat transfer from the surface is proportional to the local surface temperature, is considered. The transformed
boundary layer equations in the form of partial differential equations are solved numerically using an implicit finite-difference
scheme. Numerical solutions are obtained for the local wall temperature, the local skin friction coefficient, as well as the
velocity, angular velocity and temperature profiles. The features of the flow and heat transfer characteristics for different
values of the material or micropolar parameter K, the Prandtl number Pr and the conjugate parameter γ are analyzed and discussed. 相似文献
6.
B.J. Gireesha G.K. Ramesh M. Subhas Abel C.S. Bagewadi 《International Journal of Multiphase Flow》2011
The present paper deals with the analysis of boundary layer flow and heat transfer of a dusty fluid over a stretching sheet with the effect of non-uniform heat source/sink. Here we consider two types of heating processes namely (i) prescribed surface temperature and (ii) prescribed surface heat flux. The momentum and thermal boundary layer equations of motion are solved numerically using Runge Kutta Fehlberg fourth–fifth order method (RKF45 Method). The effects of fluid particle interaction parameter, Eckert number, Prandtl number, Number of dust particle and non-uniform heat generation/absorption parameter on temperature distribution are analyzed and also the effect of wall temperature gradient function and wall temperature function are tabulated and discussed. 相似文献
7.
The method of similarity solution is used to study the influence of lateral mass flux and thermal dispersion on non-Darcy
natural convection over a vertical flat plate in a fluid saturated porous medium. Forchheimer extension is considered in the
flow equations and the coefficient of thermal diffusivity has been assumed to be the sum of molecular diffusivity and the
dispersion thermal diffusivity due to mechanical dispersion. The suction/injection velocity distribution has been assumed
to have power function form Ax
l
, where x is the distance from the leading edge and the wall temperature distribution is assumed to be uniform. When l=−1/2, similarity solution is possible, and the results indicate that the boundary layer thickness decreases where as the
heat transfer rate increases as the mass flux parameter passes from injection domain to the suction domain. The increase in
the thermal dispersion parameter is observed to enhance the heat transfer. The combined effect of thermal dispersion and fluid
suction/injection on the heat transfer rate is discussed.
Received on 9 September 1996 相似文献
8.
Summary The effect of surface mass flux on the non-Darcy natural convection over a horizontal flat plate in a saturated porous medium
is studied using similarity solution technique. Forchheimer extension is considered in the flow equations. The suction/injection
velocity distribution has been assumed to have power function form Bx
l
, similar to that of the wall temperature distribution Ax
n
, where x is the distance from the leading edge. The thermal diffusivity coefficient has been assumed to be the sum of the molecular
diffusivity and the dynamic diffusivity due to mechanical dispersion. The dynamic diffusivity is assumed to vary linearly
with the velocity component in the x direction, i.e. along the hot wall. For the problem of constant heat flux from the surface (n=1/2), similarity solution is possible when the exponent l takes the value −1/2. Results indicate that the boundary layer thickness decreases whereas the heat transfer rate increases
as the mass flux parameter passes from the injection domain to the suction domain. The increase in the thermal dispersion
parameter is observed to favor the heat transfer by reducing the boundary layer thickness. The combined effect of thermal
dispersion and fluid suction/injection on the heat transfer rate is discussed.
Received 7 December 1995; accepted for publication 7 January 1997 相似文献
9.
This paper presents both a numerical and analytical study in connection with the steady boundary layer flow and heat transfer
induced by a moving permeable semi-infinite flat plate in a parallel free stream. Both the velocities of the flat plate and
the free stream are proportional to x
1/3. The surface temperature is assumed to be constant. The governing partial differential equations are converted into ordinary
differential equations by a new similarity transformation. Numerical results for the flow and heat transfer characteristics
are obtained for various values of the moving parameter, transpiration parameter and the Prandtl number. Approximate analytical
solutions are also obtained when the suction or injection parameter is very large. It is found that dual solutions exist for
the case when the fluid and the plate move in the opposite directions. 相似文献
10.
Kai-Long Hsiao 《International Journal of Non》2011,46(1):1-8
A magnetic hydrodynamic (MHD) mixed convective heat transfer problem of a second-grade viscoelastic fluid past a wedge with porous suction or injection has been studied. Governing equations include continuity equation, momentum equation and energy equation of the fluid. It has been analyzed by a combination of a series expansion method, the similarity transformation and a second-order accurate finite-difference method. Solutions of wedge flow on the wedge surface have been obtained by a generalized Falkner-Skan flow derivation. Some important parameters have been discussed by this study, which include the Prandtl number (Pr), the elastic number (E), the free convection parameter (G) and the magnetic parameter (M), the porous suction and injection parameter (C) and the wedge shape factor (β). Results indicated that elastic effect (E) in the flow could increase the local heat transfer coefficient and enhance the heat transfer of a wedge. In addition, similar to the results from Newtonian fluid flow and conduction analysis of a wedge, better heat transfer is obtained with a larger G and Pr. 相似文献
11.
M. Chandrasekar 《Heat and Mass Transfer》2003,40(1-2):157-165
The Governing Principle of Dissipative Processes (GPDP) formulated by Gyarmati into non-equilibrium thermodynamics is employed
to study the effects of heat transfer, two dimensional, laminar and constant property fluid flow in the boundary layer with
suction and injection. The flow and temperature fields inside the boundary layer are approximated by simple third degree polynomial
functions and the variational principle is formulated over the region of the boundary layer. The Euler–Lagrange equations
of the principle are obtained as polynomial equations in terms of momentum and thermal layer thicknesses. These equations
are solvable for any given values of Prandtl number Pr, wedge angle parameter m and suction/injection parameter H. The obtained
analytical solutions are compared with known numerical solutions and the comparison shows the fact that the accuracy is remarkable. 相似文献
12.
Chien-Hsin Chen 《Heat and Mass Transfer》2003,39(8-9):791-796
In this paper the problem of momentum and heat transfer in a thin liquid film of power-law fluid on an unsteady stretching
surface has been studied. Numerical solutions are obtained for some representative values of the unsteadiness parameter S and the power-law index n for a wide range of the generalized Prandtl number, 0.001 ≤ Pr ≤ 1000. Typical temperature and velocity profiles, the dimensionless film thickness, free-surface temperature, and the surface
heat fluxes are presented at selected controlling parameters. The results show that increasing the value of n tends to increase the boundary-layer thickness and broadens the temperature distributions. The free-surface temperature of
a shear thinning fluid is larger than that of a Newtonian fluid, but the opposite trend is true for a shear thickening fluid.
For small generalized Prandtl numbers, the surface heat flux increases with a decrease in n, but the impacts of n on the heat transfer diminish for Pr greater than a moderate value (approximately 1 ≤ Pr ≤ 10, depending on the magnitude of S). 相似文献
13.
The double diffusion effect on the mixed convection flow over a horizontal porous sensor surface placed inside a horizontal channel is analyzed.With the appropriate transformations,the unsteady equations governing the flow are reduced to non-similar boundary layer equations which are solved numerically for the time-dependent mixed convection parameter.The asymptotic solutions are obtained for small and large values of the time-dependent mixed convection parameter.The results are discussed in terms of the skin friction,the heat transfer coefficient,the mass transfer coefficient,and the velocity,temperature,and concentration profiles for different values of the Prandtl number,the Schmidt number,the squeezing index,and the mixed convection parameter. 相似文献
14.
In the present work, the effect of MHD flow and heat transfer within a boundary layer flow on an upper-convected Maxwell (UCM)
fluid over a stretching sheet is examined. The governing boundary layer equations of motion and heat transfer are non-dimensionalized
using suitable similarity variables and the resulting transformed, ordinary differential equations are then solved numerically
by shooting technique with fourth order Runge–Kutta method. For a UCM fluid, a thinning of the boundary layer and a drop in
wall skin friction coefficient is predicted to occur for higher the elastic number. The objective of the present work is to
investigate the effect of Maxwell parameter β, magnetic parameter Mn and Prandtl number Pr on the temperature field above the sheet. 相似文献
15.
An analysis is presented to describe the boundary layer flow and heat transfer towards a porous exponential stretching sheet. Velocity and thermal slips are considered instead of no-slip conditions at the boundary. Thermal radiation term is incorporated in the temperature equation. Similarity transformations are used to convert the partial differential equations corresponding to the momentum and heat equations into highly non-linear ordinary differential equations. Numerical solutions of these equations are obtained by shooting method. It is found that the fluid velocity and temperature decrease with increasing slip parameter. Temperature is found to decrease with an increase of thermal slip parameter. Thermal radiation enhances the effective thermal diffusivity and the temperature rises. 相似文献
16.
B. SAHOO S.PONCET 《应用数学和力学(英文版)》2013,34(12):1465-1480
This investigation deals with the effects of slip, magnetic field, and non- Newtonian flow parameters on the flow and heat transfer of an incompressible, electrically conducting fourth-grade fluid past an infinite porous plate. The heat transfer analysis is carried out for two heating processes. The system of highly non-linear differential equations is solved by the shooting method with the fourth-order Runge-Kutta method for moderate values of the parameters. The effective Broyden technique is adopted in order to improve the initial guesses and to satisfy the boundary conditions at infinity. An exceptional cross-over is obtained in the velocity profile in the presence of slip. The fourth-grade fluid parameter is found to increase the momentum boundary layer thickness, whereas the slip parameter substantially decreases it. Similarly, the non-Newtonian fluid parameters and the slip have opposite effects on the thermal boundary layer thickness. 相似文献
17.
The boundary layer flow and heat transfer of a fluid through a porous medium towards a stretching sheet in presence of heat
generation or absorption is considered in this analysis. Fluid viscosity is assumed to vary as a linear function of temperature.
The symmetry groups admitted by the corresponding boundary value problem are obtained by using a special form of Lie group
transformations viz. scaling group of transformations. These transformations are used to convert the partial differential
equations corresponding to the momentum and the energy equations into highly non-linear ordinary differential equations. Numerical
solutions of these equations are obtained by shooting method. It is found that the horizontal velocity decreases with increasing
temperature-dependent fluid viscosity parameter up to the crossing-over point but increases after that point and the temperature
decreases in this case. With the increase of permeability parameter of the porous medium the fluid velocity decreases but
the temperature increases at a particular point of the sheet. Effects of Prandtl number on the velocity boundary layer and
on the thermal boundary layer are studied and plotted. 相似文献
18.
M. M. Rahman 《Meccanica》2011,46(5):1127-1143
This paper presents heat transfer process in a two-dimensional steady hydromagnetic convective flow of an electrically conducting
fluid over a flat plate with partial slip at the surface of the boundary subjected to the convective surface heat flux at
the boundary. The analysis accounts for both temperature-dependent viscosity and temperature dependent thermal conductivity.
The local similarity equations are derived and solved numerically using the Nachtsheim-Swigert iteration procedure. Results
for the dimensionless velocity, temperature and ambient Prandtl number within the boundary layer are displayed graphically
delineating the effect of various parameters characterizing the flow. The results show that momentum boundary layer thickness
significantly depends on the surface convection parameter, Hartmann number and on the sign of the variable viscosity parameter.
The results also show that plate surface temperature is higher when there is no slip at the plate compared to its presence.
For both slip and no-slip cases surface temperature of the plate can be controlled by controlling the strength of the applied
magnetic field. In modelling the thermal boundary layer flow with variable viscosity and variable thermal conductivity, the
Prandtl number must be treated as a variable irrespective of flow conditions whether there is slip or no-slip at the boundary
to obtain realistic results. 相似文献
19.
The flow and heat transfer for an electrically conducting fluid with a porous substrate and a flat plate under the influence of magnetic field is considered. The magnetic field is assumed to be uniform and also along normal to the surface. The momentum and energy equations are transformed to ordinary differential equations by using suitable similarity transformation and are solved by standard techniques. But the energy equation is solved by considering two boundary layers, one in the porous substrate and the other above the porous substrate. Numerical results are presented through graphs with various values of magnetic parameter for both velocity and thermal boundary layers along with Nusselt number and for various values of Prandtl number and Eckert number in thermal boundary layer. 相似文献
20.
The paper discusses the statistical steady heat and momentum transfer problem in the inlet section of the plastic tubes.
The modified two equation k–ɛ turbulent model utilizing variability of turbulent Prandtl number, Prt, was used for the analysis. Considering the thermophysical anisotropy of the tube material, a balance of local temperatures
and local heat fluxes on the boundary between the fluid and the tube wall was assumed (conjugate heat transfer problem). The
thermal boundary condition on the external surface of the tube (temperature) measured in the experiment was taken into account.
The boundary problem described was solved by the control volume method. The values of the parameters of Pr and Re obtained
from the experiments were included in the numerical calculations. Based on the results obtained, profiles of mean fluid temperatures,
local Nusselt numbers on the internal and external surface of the tube, and profiles of temperatures on the internal surface
of the tube and inside of the tube wall were determined. The analysis shows that changes in Prtand turbulence intensity, Tu, influence the local values of Nusselt numbers, and it also shows that the results for the local
Nusselt numbers inside the tube obtained from numerical calculations are of great accuracy in comparison with results published
in the available literature.
Received on 11 June 2001 相似文献