共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
An analysis is performed to study the heat transfer characteristics of steady two-dimensional boundary layer flow past a moving permeable flat plate in a nanofluid. The effects of uniform suction and injection on the flow field and heat transfer characteristics are numerically studied by using an implicit finite difference method. It is found that dual solutions exist when the plate and the free stream move in the opposite directions. The results indicate that suction delays the boundary layer separation, while injection accelerates it. 相似文献
3.
Numerical modeling of the time-dependent supersonic flow over a compression corner with different roundness radii is performed on the basis of the solution of the two-dimensional Navier-Stokes equations in the regimes corresponding to local boundary layer separation. The development of unstable disturbances generated by local periodic injection/suction in the preseparated boundary layer is calculated. The results are compared with those of similar calculations for a flat plate. It is shown that the natural oscillations of the boundary-layer second mode stabilize in the separation zone and grow intensely downstream of the reattachment point. The acoustic modes excited within a separation bubble are studied using numerical calculations and an asymptotic analysis. 相似文献
4.
Heat transfer analysis has been presented for the boundary layer forced convective flow of an incompressible fluid past a
plate embedded in a porous medium. The similarity solutions for the problem are obtained and the reduced nonlinear ordinary
differential equations are solved numerically. In case of porous plate, fluid velocity increases for increasing values of
suction parameter whereas due to injection, fluid velocity is noticed to decrease. The non-dimensional temperature increases
with the increasing values of injection parameter. A novel result of this investigation is that the flow separation occurred
due to suction/injection may be controlled by increasing the permeability parameter of the medium. The effect of thermal radiation
on temperature field is also analyzed. 相似文献
5.
Mohsen Nazari Esmaeel Shakerinejad Morteza Nazari D. Andrew S. Rees 《Transport in Porous Media》2013,98(1):223-238
This paper is concerned with the thermal non-equilibrium free convection boundary layer, which is induced by a vertical heated plate embedded in a saturated porous medium. The effect of suction or injection on the free convection boundary layer is also studied. The plate is assumed to have a linear temperature distribution, which yields a boundary layer of constant thickness. On assuming Darcy flow, similarity solutions are obtained for governing the steady laminar boundary layer equations. The reduced Nusselt numbers for both the solid and fluid phases are calculated for a wide range of parameters, and compared with asymptotic analyses. 相似文献
6.
Burhan uhadarolu Yahya Erkan Akansu Ahmet
mür Turhal 《Experimental Thermal and Fluid Science》2007,31(8):909-915
It is well known that injection/suction (transpiration) through a perforated surface is an efficient way of influencing the characteristics of a turbulent boundary layer. Injection application creates a thicker boundary layer on a flat plate and it thus decreases drag. In aeronautical applications, suction is frequently used to delay boundary layer separation. This paper presents an experimental study on the effects of uniform injection through one perforated surface of a square cylinder on the pressure distribution and drag coefficient in a two-dimensional turbulent flow. For this purpose, surface pressure measurements around a square cylinder have been performed at three different Reynolds numbers in a wind tunnel. The parameters taken into account were injection rate, position of perforated surface (i.e., front, top, and rear), and pressure coefficient and drag coefficient. The results show that variation in pressure coefficient around the square cylinder and drag coefficient were influenced by the position of perforated surface and by injection rate. 相似文献
7.
A boundary layer analysis has been presented to study the influence of thermal radiation and lateral mass flux 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 Rosseland approximation is used to describe the radiative heat flux in the energy equation. Similarity
solution for the transformed governing equations is obtained and the combined effect of thermal radiation and fluid suction/injection
on the heat transfer rate is discussed. Numerical results for the details of the velocity and temperature profiles as well
as Nusselt number have been presented.
Received on 7 July 1999 相似文献
8.
In this paper, we consider the control of laminar, incompressible boundary layer for the ionized air flow over a flat plate and wedges through the application of an electric field. Group theory is used to find equivalence transformations of the resulting boundary layer equations. These transformations in turn reveal forms of the electric field function which lead to reductions of the equations via similarity variables. Differences in boundary layer thickness growth and velocity profiles as well as wall shear stresses are shown for the specific choices of the electric field function. The effects of suction and blowing type of boundary conditions are also demonstrated. The applied electric fields lead to a thinning of boundary layer thickness and an increase in wall shear stress. They are also shown to stabilize the velocity component profiles and suppress flow separation in reentrant corners. 相似文献
9.
In this study, laminar boundary layer flow over a flat plate embedded in a fluid-saturated porous medium in the presence of
viscous dissipation, inertia effect and suction/injection is analyzed using the Keller box finite difference method. The flat
plate is assumed to be held at constant temperature. The non-Darcian effects of convection, boundary and inertia are considered.
Results for the local heat transfer parameter and the local skin friction parameter as well as the velocity and temperature
profiles are presented for various values of the governing parameters. The non-Darcian effects are shown to decrease the velocity
and to increase the temperature. It is also shown that the local heat transfer parameter and the local skin friction parameter
increase due to suction of fluid while injection reverses this trend. It is disclosed that the effect of the viscous dissipation
for negative values of Ec (T
w
< T
∞) is to enhance the heat transfer coefficient while the opposite is true for positive values of Ec (T
w
> T
∞). The results are compared with those available in the existing literature and an excellent agreement is obtained. 相似文献
10.
The effect of pulse-width modulated (PWM) blowing/suction through a hole in a flat plate, above which a Blasius boundary layer develops, is studied. A hot wire is used to measure the streamwise velocity downstream of the hole. The PWM blowing/suction is found to create amplitude-modulated variations in the streamwise velocity, which are well correlated with the signal generating the disturbance. 相似文献
11.
The problem of the steady flow of three classes of non-linear fluids of the differential type past a porous plate with uniform suction or injection is studied. The flow which is studied is the counterpart of the classical ‘asymptotic suction’ problem, within the context of the non-Newtonian fluid models. The non-linear differential equations resulting from the balance of momentum and mass, coupled with suitable boundary conditions, are solved numerically either by a finite difference method or by a collocation method with a B-spline function basis. The manner in which the various material parameters affect the structure of the boundary layer is delineated. The issue of paucity of boundary conditions for general non-linear fluids of the differential type, and a method for augmenting the boundary conditions for a certain class of flow problems, is illustrated. A comparison is made of the numerical solutions with the solutions from a regular perturbation approach, as well as a singular perturbation. 相似文献
12.
Effect of a two-dimensional smooth hump on linear instability of hypersonic boundary layer is studied by using parabolized stability equations. Linear evolution of mode S over a hump is analyzed for Mach 4.5 and 5.92 flat plate and Mach 7.1 sharp cone boundary layers. Mean flow for stability analysis is obtained by solving the parabolized Navier–Stokes equations. Hump with height smaller than local boundary layer thickness is considered. The case of flat plate and sharp cone without the hump are also studied to provide comparable data. For flat plate boundary layers, destabilization and stabilization effect is confirmed for hump located at upstream and downstream of synchronization point, respectively. Results of parametric studies to examine the effect of hump height, location, etc., are also given. For sharp cone boundary layer, stabilization influence of hump is also identified for a specific range of frequency. Stabilization influence of hump on convective instability of mode S is found to be a possible cause of previous experimental observations of delaying transition in hypersonic boundary layers. 相似文献
13.
Summary A boundary layer problem of a nonnewtonian fluid flow with fluid injection on a semi-infinite flat plate whose surface moves
with a constant velocity in the opposite direction to that of the uniform mainstream is analyzed. Concluding similarity equations
are solved numerically to show the dependence of the problem to the velocity ratio λ of the plate to uniform flow and to the
injection velocity parameter C. The critical values of λ and C for each nonnewtonian power-law index n are obtained, and their significance in drag reduction is discussed.
Received 26 August 1997; accepted for publication 21 October 1998 相似文献
14.
In this paper the study of visco-elastic (Walters' liquid B model) flow past a stretching plate with suction is considered. Exact solutions of the boundary layer equations of motion and energy are obtained. The expressions for the coefficient of skin friction and of boundary layer thickness are obtained. 相似文献
15.
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
16.
The effects of magnetic field, suction/injection, nanoparticles type, and nanoparticle volume fraction on heat transfer characteristics and mechanical properties of a moving surface embedded into cooling medium consists of water with Cu, Ag or Al2O3 particles are studied. The governing boundary layer equations are transformed to ordinary differential equations containing, suction/injection parameter, magnetic parameter, nanoparticle and volume fraction. These equations are solved analytically. The velocity and temperature profiles within the boundary layer are plotted and discussed in details for various values of the different parameters. 相似文献
17.
K. S. Sastri 《Applied Scientific Research》1965,14(1):126-132
Summary An analytical study has been made to estimate the effect of suction on heat transfer in the laminar boundary layer on a flat plate when the fluid is flowing with heat sources in it. Results have been obtained for Prandtl number equal to unity when the suction parameter is greater than 3. 相似文献
18.
V. V. Terekhov V. I. Terekhov 《Journal of Applied Mechanics and Technical Physics》2017,58(2):254-263
The structure and heat transfer in a turbulent separated flow in a suddenly expanding channel with injection (suction) through a porous wall are numerically simulated with the use of two-dimensional averaged Navier–Stokes equations, energy equations, and v 2–f turbulence model. It is shown that enhancement of the intensity of the transverse mass flux on the wall reduces the separation region length in the case of suction and increases the separation region length in the case of injection up to complete boundary layer displacement. The maximum heat transfer coefficient as a function of permeability is accurately described by the asymptotic theory of a turbulent boundary layer. 相似文献
19.
The growth of two-dimensional disturbances generated in a supersonic (M = 6) boundary layer on a flat plate by a periodic perturbation of the injection/suction type is investigated on the basis of a numerical solution of the Navier-Stokes equations. For small initial perturbation amplitudes, the second-mode growth rate obtained from the numerical modeling coincides with the growth rate calculated using linear theory with account for the non-parallelism of the main flow. Calculations performed for large initial perturbation amplitudes reveal the nonlinear dynamics of the perturbation growth downstream, with rapid growth of the higher multiple harmonics.Translated from Izvestiya Rossiiskoi Academii Nauk, Mekhanika Zhidkosti i Gaza, No. 6, 2004, pp. 33–44. Original Russian Text Copyright © 2004 by Egorov, Sudakov, Fedorov. 相似文献
20.
A.A. Bakchinov K.J.A. Westin V.V. Kozlov P.H. Alfredsson 《European Journal of Mechanics - B/Fluids》1998,17(6):847
Previous studies on boundary layer transition at moderate levels of free stream turbulence (FST) have shown that the transition process can be promoted by the introduction of Tollmien-Schlichting (TS) waves. In the present work the interaction between localized boundary layer disturbances and controlled TS-waves is studied experimentally. The localized disturbances are generated either from a controlled free stream perturbation, or by means of suction or injection through a slot in the flat plate surface. Both methods result in boundary layer disturbances dominated by elongated streamwise streaks of high and low velocity in the streamwise component. A strong interaction is observed preferably for high frequency TS-waves, which are damped when generated separately, and the interaction starts as a local amplification of a wide band of low-frequency oblique waves. The later stages of the transition process can be identified as a non-linear interaction between the oblique structures, leading to regeneration of new and stronger streamwise streaks. 相似文献