共查询到20条相似文献,搜索用时 31 毫秒
1.
This letter is concerned with the plane and axisymmetric stagnation-point flows and heat transfer of an electrically-conducting
fluid past a stretching sheet in the presence of the thermal radiation and heat generation or absorption. The analytical solutions
for the velocity distribution and dimensionless temperature profiles are obtained for the various values of the ratio of free
stream velocity and stretching velocity, heat source parameter, Prandtl number, thermal radiation parameter, the suction and
injection velocity parameter and magnetic parameter and dimensionality index in the series form with the help of homotopy
analysis method (HAM). Convergence of the series is explicitly discussed. In addition, shear stress and heat flux at the surface
are calculated. 相似文献
2.
N. V. Malai K. S. Ryazanov E. R. Shchukin A. A. Stukalov 《Journal of Applied Mechanics and Technical Physics》2011,52(4):553-559
The flow around a heated spherical drop in a viscous non-isothermal gaseous medium with uniformly distributed constant-power
heat sources (sinks) acting inside is theoretically described in the Stokes approximation. It is assumed that the mean temperature
of the drop surface can differ substantially from the temperature of the ambient gaseous medium. An analytical expression
for the drag force and drift velocity in the gravity field is derived by solving hydrodynamic equations with allowance for
the temperature dependence of viscosity, thermal conductivity, and density of the gaseous medium. 相似文献
3.
The nonsimilar non-Darcian free-convection flow about a vertical cylinder with impermeable surface embedded in a saturated porous medium, where surface temperature of the cylinder varies as xm, a power function of distance from the leading edge, has been studied by employing the implicit finite-difference method together with the Newton's quasilinearization technique. In the present investigation, effects of the surface mass flux together with the inertial effects on the rate of heat transfer at the surface, on the velocity distribution, and on the temperature distribution are shown graphically. 相似文献
4.
The present study is devoted to investigate the influences of mass transfer on buoyancy induced flow over vertical flat plate
embedded in a non-Newtonian fluid saturated porous medium. The Ostwald–de Waele power-law model is used to characterize the
non-Newtonian fluid behavior. Similarity solution for the transformed governing equations is obtained with prescribed variable
surface heat flux. Numerical results for the details of the velocity, temperature and concentration profiles are shown on
graphs. Excess surface temperature as well as concentration gradient at the wall associated with heat flux distributions,
which are entered in tables, have been presented for different values of the power-law index n, buoyancy ration B and the exponent λ as well as Lewis number Le.
Received on 26 April 2000 相似文献
5.
This article considers the problem of mixed convection stagnation-point flow towards a vertical plate embedded in a porous
medium with prescribed surface heat flux. It is assumed that the free stream velocity and the surface heat flux vary linearly
from the stagnation point. Using a similarity transformation, the governing system of partial differential equations is transformed
into a system of ordinary differential equations, before being solved numerically by a finite-difference method. The features
of the flow and the heat transfer characteristics are analyzed and discussed. It is found that dual solutions exist for both
buoyancy assisting and opposing flows. 相似文献
6.
Julian Reinheimer 《Applied Scientific Research》1964,13(1):203-208
Summary The problem of the phase change produced in semi-infinite media by volume heat sources is considered for quasi steady state conditions and where the molten or sublimated material is removed as soon as it is formed. A general formal solution for the temperature distribution and the velocity of the phase change surface is presented, and it is shown that for source functions of physical interest the velocity of the surface is the ratio of the total heat flux to the energy required to produce the phase change of a unit volume of material. Several examples are considered. 相似文献
7.
I-Chung Liu 《International Journal of Non》2005,40(4):465-474
An analysis is performed for flow and heat transfer of a steady laminar boundary layer flow of an electrically conducting fluid of second grade in a porous medium subject to a transverse uniform magnetic field past a semi-infinite stretching sheet with power-law surface temperature or power-law surface heat flux. The effects of viscous dissipation, internal heat generation of absorption and work done due to deformation are considered in the energy equation. The variations of surface temperature gradient for the prescribed surface temperature case (PST) and surface temperature for the prescribed heat flux case (PHF) with various parameters are tabulated. The asymptotic expansions of the solutions for large Prandtl number are also given for the two heating conditions. It is shown that, when the Eckert number is large enough, the heat flow may transfer from the fluid to the wall rather than from the wall to the fluid when Eckert number is small. A physical explanation is given for this phenomenon. 相似文献
8.
The effect of thermal radiation on the non-Darcy mixed convection flow over a non-isothermal horizontal surface immersed in a saturated porous medium has been studied. The wall temperature is assumed to have a power-law variation with the distance measured from the leading edge of the plate. The non-linear coupled parabolic partial differential equations governing the flow have been solved numerically using a finite-difference scheme. For some particular cases, the self-similar solution has also been obtained. The heat transfer is found to be strongly influenced by the radiative flux number, buoyancy parameter, variation of wall temperature, non-Darcy parameter and the nature of the free stream velocity. 相似文献
9.
The present study is devoted to investigate the influences of viscous dissipation on buoyancy induced flow over a horizontal or a vertical flat plate embedded in a non-Newtonian fluid saturated porous medium. The Ostwald-de Waele power-law model is used to characterize the non-Newtonian fluid behavior. Similarity solutions for the transformed governing equations are obtained with prescribed variable surface temperature (PT) or with prescribed variable surface heat flux (PHF) for the horizontal plate case. While, the similarity solutions are obtained with prescribed variable surface heat flux for the vertical plate case. Different similar transformations, for each case, are used. Numerical results for the details of the velocity and temperature profiles are shown on graphs. Nusselt number associated with temperature distributions and excess surface temperature associated with heat flux distributions which are entered in tables have been presented for different values of the power-law index n and the exponent as well as Eckert number. 相似文献
10.
On moving heat sources 总被引:1,自引:0,他引:1
The two-dimensional thermal problem due to relative motion of a medium and a suddenly activated circular heat source is solved
for several boundary conditions. The solutions can be interpreted as for a moving heat source in a stationary medium or a
medium moving past a stationary heat source.
Uniform and non-uniform temperature, and uniform and non-uniform heat flux boundary conditions are considered. The effect
of velocity and radial direction on the temperature distribution is examined. Average, steady-state Nusselt numbers are derived.
The transient response of a continuous line source is obtained as a limiting case of the prescribed heat flux solution.
Received on 24 September 1996 相似文献
11.
12.
An analysis is made of the steady two-dimensional stagnation-point flow of an incompressible viscoelastic fluid over a flat
deformable surface when the surface is stretched in its own plane with a velocity proportional to the distance from the stagnation-point.
It is shown that for a viscoelastic conducting fluid of short memory (obeying Walters’ Bʹ model), a boundary layer is formed
when the stretching velocity of the surface is less than the inviscid free-stream velocity and velocity at a point increases
with increase in the Hartmann number. On the other hand an inverted boundary layer is formed when the surface stretching velocity
exceeds the velocity of the free stream and the velocity decreases with increase in the Hartmann number. A novel result of
the analysis is that the flow near the stretching surface is that corresponding to an inviscid stagnation-point flow when
the surface stretching velocity is equal to the velocity of the free stream. Temperature distribution in the boundary layer
is found when the surface is held at constant temperature and surface heat flux is determined. It is found that in the absence
of viscous and Ohmic dissipation and strain energy in the flow, temperature at a point decreases with increase in the Hartmann
number. 相似文献
13.
14.
A numerical solution, for incompressible, steady-state, laminar flow heat transfer in the combined entrance region of a circular tube is presented for the case of constant wall heat flux and constant wall temperature. The development of velocity profile is obtained from Sparrow's entrance region solution. This velocity distribution is used in solving the energy equation numerically to obtain temperature profiles. Variation of the heat transfer coefficient for these two different boundary conditions for the early stages of boundary layer formation on the pipe wall is obtained. Local Nusselt numbers are calculated and the results are compared with those given byUlrichson andSchmitz. The effect of the thermal boundary conditions is studied by comparing the uniform wall heat flux results with uniform wall temperature. 相似文献
15.
M. A. Sheremet 《Journal of Applied Mechanics and Technical Physics》2012,53(4):566-576
Conjugate thermogravitational convection in a horizontal cylinder with two sources of energy with a constant temperature under conditions of convective heat exchange with the ambient medium is numerically analyzed. The mathematical model is formulated in the dimensionless variables of the stream function-vorticity vector-temperature. The influence of the governing parameters (Rayleigh and Prandtl numbers, temperature of energy sources, time, and relative thermal conductivity) both on the local thermohydrodynamic characteristics (streamlines and temperature field) and on the integral parameter (mean Nusselt number on the surface of heat sources) is analyzed. 相似文献
16.
The problem of non-Darcy natural convection adjacent to a vertical cylinder embedded in a thermally stratified porous medium
has been analyzed. Nonsimilarity solutions are obtained for the case that the ambient temperature increases linearly with
height of the cylinder. A generalized flow model was used in the present study to include the effects of the macroscopic viscous
term and the microscopic inertial force. Also, the thermal dispersion effect is considered in the energy equation. Thus, the
main aim of this work is to examine the effects of thermal stratification and non-Darcy flow phenomena on the free convection
flow and heat transfer characteristics. It was found that the present problem depends on six parameters, namely, the local
thermal stratification parameter ξ, the boundary effect parameter Bp, the modified Grashof number Gr*, wall temperature exponent m, the curvature parameter ω, and the modified Rayleigh number based on pore diameter Ra
d
. The impacts of these governing parameters on the local heat transfer parameter are discussed in great detail. Also, representative
velocity and temperature profiles are presented at selected values of the thermal stratification parameter. In general, the
local heat transfer parameter is increased with increasing the values of m, ω, and Ra
d
; while it is decreased with increasing the values of ξ, Bp, and Gr*.
Received on 19 May 1998 相似文献
17.
Steady two-dimensional stagnation-point flow of an incompressible viscous fluid over a flat deformable sheet is investigated
when the sheet is stretched in its own plane with a velocity proportional to the distance from the stagnation-point. It is
shown that for a fluid of small kinematic viscosity, a boundary layer is formed when the stretching velocity is less than
the free stream velocity and an inverted boundary layer is formed when the stretching velocity exceeds the free stream velocity.
Temperature distribution in the boundary layer is found when the surface is held at constant temperature and surface heat
flux is determined.
Received on 12 July 2000 / Published online: 29 November 2001 相似文献
18.
The present paper is concerned with the study of radiation effects on the combined (forced-free) convection flow of an optically
dense viscous incompressible fluid over a vertical surface embedded in a fluid saturated porous medium of variable porosity
with heat generation or absorption. The effects of radiation heat transfer from a porous wall on convection flow are very
important in high temperature processes. The inclusion of radiation effects in the energy equation leads to a highly non-linear
partial differential equations which are transformed to a system of ordinary differential equations using non-similarity transformation.
These equations are then solved numerically using implicit finite-difference method subject to appropriate boundary and matching
conditions. A parametric study of the physical parameters such as the particle diameter-based Reynolds number, the flow based
Reynolds number, the Grashof number, the heat generation or absorption co-efficient and radiation parameter is conducted on
temperature distribution. The effects of radiation and other physical parameters on the local skin friction and on local Nusselt
number are shown graphically. It is interesting to observe that the momentum and thermal boundary layer thickness increases
with the radiation and decrease with increase in the Prandtl number. 相似文献
19.
Tom Bajcar Brane Širok Marko Hočevar Ferdinand Trenc 《Flow, Turbulence and Combustion》2008,80(1):3-19
The paper presents a study of heat transfer between the turbulent airflow and the inner wall surface of an axial diffuser
rotating around its longitudinal axis. Heat transfer was assessed through the measurement of a time-dependent temperature
field of the diffuser inner wall surface. Measurements of the instantaneous flow velocity components were performed by a laser–Doppler
anemometry system, which delivered information on mean velocity components as well as on the turbulence intensity. A significant
increase of all three mean velocity components was observed near the rotating diffuser wall in comparison with a non-rotating
diffuser. Temperature field measurements were carried out by means of infrared thermography. The experiment showed a significant
dependence of the temperature field on the turbulent flowfield induced by diffuser rotation. A strong influence of the flow
separation and reattachment on the temperature distribution was observed, while rotation was found to suppress the occurrence
of flow separation from the diffuser wall. Properties of the velocity field such as turbulent kinetic energy were directly
coupled with the temperature distribution in order to gain the information on how to enhance or reduce heat transfer by changing
the integral parameters of the diffuser (e.g. rotation frequency or amount of flow). 相似文献
20.
Dr.-Ing. V. Javeri 《Heat and Mass Transfer》1974,7(4):226-235
The combined influence of viscosity, Hall effect and ion slip on hydrodynamic fields and on heat transfer is investigated. The exact solutions for velocity, induced magnetic field and temperature are derived for the laminar MHD flow in a flat channel assuming a small magnetic Reynolds number, finely segmented electrodes, fully developed flow and uniform heat flux at channel walls. The internal generation of heat is not considered. The Kantorowitsch method of variational calculus is employed to approximate the complicated velocity distribution. 相似文献