共查询到20条相似文献,搜索用时 15 毫秒
1.
In this paper, a direct numerical simulation of particle-laden flow in a flat plate boundary layer is performed, using the Eulerian–Lagrangian point-particle approach. This is, as far as we know, the first simulation of a particle-laden spatially-developing turbulent boundary layer with two-way coupling. A local minimum of the particle number density is observed in the close vicinity of the wall. The present simulation results indicate that the inertial particles displace the quasi-streamwise vortices towards the wall, which, in turn, enhance the mean streamwise fluid velocity. As a result, the skin-friction coefficient is increased whereas the boundary layer integral thicknesses are reduced. The presence of particles augments the streamwise fluctuating velocity in the near-wall region but attenuates it in the outer layer. Nevertheless, the wall-normal and spanwise velocity fluctuations are significantly damped, and so is the Reynolds stress. In addition, the combined effect of a reduced energy production and an increased viscous dissipation leads to the attenuation of the turbulent kinetic energy. 相似文献
2.
Effects of Hall current on MHD free convection boundary layer flow of a viscous incompressible electrically conducting fluid past a heated vertical flat plate of finite dimension in the presence of a uniform transverse magnetic field have been studied. An exact solution of the governing equations describing the flow has been obtained. The velocity field, induced magnetic field and bulk temperature distributions in the boundary layer flow have been discussed. It is found that the velocity components increase with an increase in Hall parameter. It is noticed that the induced magnetic field components are radically influenced by the Hall parameter. It is also found that the magnitude of bulk temperature in the x-direction decreases with an increase in either Hall parameter or magnetic parameter. On the other hand, the magnitude of the bulk temperature in the z-direction increases with an increase in Hall parameter whereas it decreases with an increase in magnetic parameter. 相似文献
3.
A new approach on MHD natural convection boundary layer flow from a finite flat plate of arbitrary inclination in a rotating
environment, is presented. This problem plays a significant role on boundary layer flow control. It is shown that taking into
account the pressure rise region at the leading edge of the plate leads to avoid separation and the back flow is reduced by
the strong magnetic field. It is also shown that the frictional drag at the leading edge of the plate is reduced when the
inclination angle α=π/4. In the case of isothermal flat plate, the bulk temperature becomes identical for any value of Gr (Grashof number) when the value of M
2 (Hartmann number) and K
2 (rotation parameter) are kept fixed. 相似文献
4.
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
5.
The influences of variable viscosity and buoyancy force on laminar boundary layer flow and heat transfer due to a continuous flat plate are examined. The deviation of the velocity and temperature fields as well as of the skin friction and heat transfer results from their constant values are determined by means of similarity solutions. 相似文献
6.
7.
A. D. Savel’ev 《Fluid Dynamics》2007,42(6):907-913
Supersonic laminar flow past a two-dimensional “flat-plate/wedge“ configuration is numerically investigated. The pressures at the boundary layer separation and reattachment points are calculated over wide Mach and Reynolds number ranges. The minimum angles of the wedge surface inclination at which a return flow occurs are determined. The results are presented in the form of generalized Mach-number-dependences of the theoretical pressure on the wedge surface initiating boundary layer separation and the pressure at the boundary layer reattachment point. 相似文献
8.
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10.
T. Y. Na 《Applied Scientific Research》1977,33(5-6):519-543
The problem of natural convection over a semi-infinite flat plate with non-uniform wall temperature is studied by using a
numerical method. The local rates of heat transfer as a function of the distance along the plate are tabulated for a range
of Prandtl numbers (0.01 to 100) and for a few cases of wall temperature distributions. Such tabulations serve as a reference
against which other approximate solutions can be compared in the future. 相似文献
11.
Leli Deswita Roslinda Nazar Anuar Ishak Rokiah Ahmad Ioan Pop 《Heat and Mass Transfer》2010,46(8-9):1013-1018
The effects of suction/injection on steady laminar mixed convection boundary layer flow over a permeable horizontal surface of a wedge in a viscous and incompressible fluid is considered in this paper. The similarity solutions of the governing boundary layer equations are obtained for some values of the suction/injection parameter f 0, the constant exponent m of the wall temperature as well as the mixed convection parameter λ. The resulting system of nonlinear ordinary differential equations is solved numerically for both assisting and opposing flow regimes using an implicit finite-difference scheme known as the Keller-box method. Numerical results for the reduced skin friction coefficient, the local Nusselt number, and the velocity and temperature profiles are obtained for various values of parameters considered. Dual solutions are found to exist for the case of opposing flow. 相似文献
12.
In this paper, the steady magnetohydrodynamic (MHD) mixed convection boundary layer flow of an incompressible, viscous and
electrically conducting fluid over a stretching vertical flat plate is theoretically investigated with Hall effects taken
into account. The governing equations are solved numerically using an implicit finite-difference scheme known as the Keller-box
method. The effects of the magnetic parameter, the Hall parameter and the buoyancy parameter on the velocity profiles, the
cross flow velocity profiles and the temperature profiles are presented graphically and discussed. Investigated results indicate
that the Hall effect on the temperature is small, and the magnetic field and Hall currents produce opposite effects on the
shear stress and the heat transfer at the stretching surface. 相似文献
13.
Toshihiro Tsuji Tsuyoshi Kajitani Tatsuhiko Nishino 《International Journal of Heat and Fluid Flow》2007,28(6):1472-1483
An experimental study on heat transfer enhancement for a turbulent natural convection boundary layer in air along a vertical flat plate has been performed by inserting a long flat plate in the spanwise direction (simple heat transfer promoter) and short flat plates aligned in the spanwise direction (split heat transfer promoter) with clearances into the near-wall region of the boundary layer. For a simple heat transfer promoter, the heat transfer coefficients increase by a peak value of approximately 37% in the downstream region of the promoter compared with those in the usual turbulent natural convection boundary layer. It is found from flow visualization and simultaneous measurements of the flow and thermal fields with hot- and cold-wires that such increase of heat transfer coefficients is mainly caused by the deflection of flows toward the outer region of the boundary layer and the invasion of low-temperature fluids from the outer region to the near-wall region with large-scale vortex motions riding out the promoter. However, heat transfer coefficients for a split heat transfer promoter exhibit an increase in peak value of approximately 60% in the downstream region of the promoter. Flow visualization and PIV measurements show that such remarkable heat transfer enhancement is attributed to longitudinal vortices generated by flows passing through the clearances of the promoter in addition to large-scale vortex motions riding out the promoter. Consequently, it is concluded that heat transfer enhancement of the turbulent natural convection boundary layer can be substantially achieved in a wide area of the turbulent natural convection boundary layer by employing multiple column split heat transfer promoters. It may be expected that the heat transfer enhancement in excess of approximately 40% can be accomplished by inserting such promoters. 相似文献
14.
H.S. Takhar Rama Subba Reddy Gorla Professor Chairman William R. Schoren Research Assistant 《Mechanics Research Communications》1988,15(3)
Using the theory of micropolar fluids developed by Eringen, the transverse curvature effects on axisymmetric free convection boundary layer flow of a micropolar fluid past slender vertical cones are investigated. The case of constant surface heat flux is considered in this paper. Using perturbation techniques, the governing equations for momentum, angular momentum and energy have been solved numerically. Graphical representations for the velocity, angular velocity and thermal functions are presented for various physical and fluid property parameters. 相似文献
15.
Anuar Ishak 《Heat and Mass Transfer》2009,46(2):147-151
The effects of thermal radiation and thermal buoyancy on the steady, laminar boundary layer flow over a horizontal plate is
investigated. The plate temperature is assumed to be inversely proportional to the square root of the distance from the leading
edge. The set of similarity equations is solved numerically, and the solutions are given for some values of the radiation
and buoyancy parameters for Prandtl number unity. It is found that dual solutions exist for negative values of the buoyancy
parameter, up to certain critical values. Beyond these values, the solution does no longer exist. Moreover, it is found that
there is no local heat transfer at the surface except in the singular point at the leading edge. The radiation parameter is
found to increase the local Stanton number. 相似文献
16.
I. V. Pushkareva 《Journal of Applied Mechanics and Technical Physics》1970,11(3):418-422
We examine unsteady incompressible fluid flow in a laminar boundary layer with uniform suction for longitudinal flow over a flat plate when the external stream is a flow with constant velocity, on which there is superposed a sinusoidal disturbance convected by the stream, analogous to [1]. We study the stability of such flow in the boundary layer.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, Vol. 11, No. 3, pp. 66–70, May–June, 1970. 相似文献
17.
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
18.
Thickness of the thermal boundary layer on natural convection from a horizontal plate was experimentally measured and expressed
as a function of Rayleigh number both in laminar and turbulent regimes. Several parametric equations expressing the Nusselt
number as a function of Rayleigh number were developed combining experimental data by other authors with the ones obtained
in this work. The characteristic length was taken as the thickness of the thermal boundary layer in one equation and as the
ratio of the area to the perimeter in another one. Both characteristic lengths correlated the data precisely in wide ranges
of Rayleigh numbers.
相似文献
Bulent KozanogluEmail: |
19.
A Pantokratoras 《Heat and Mass Transfer》2005,41(12):1085-1094
The steady laminar boundary layer flow along a flat plate is studied taking into account the variation of fluid viscosity and fluid Prandtl number with temperature. In the forced convection case the plate moves with constant velocity and its temperature varies in power law with x. In the mixed convection case the plate temperature is constant and the fluid moves upwards due to an external free stream and due to buoyancy forces. The results are obtained with the direct numerical solution of the boundary layer equations. The study concerns the wall heat transfer, the wall shear stress and velocity and temperature profiles across the boundary layer. The results of the present work are different from those existing in the literature, which have been obtained with the assumption of constant Pr number. 相似文献
20.
Dr.-Ing. T. K. Bose 《Heat and Mass Transfer》1980,14(3):165-171
Solution of a turbulent boundary layer for a constant property, particle-laden gas flow is obtained by a differential method. A dimensionless analysis shows importance of an interaction parameter in increasing heat flux. Boundary layer analysis is done in usual manner by transforming partial differential equations and solution is started at the leading edge by Runge-Kutta method. Velocity and temperature profiles at downstream planes for gas and particles are calculated by an implicit finite-difference iterative procedure, and numerical results are compared with available experimental data. 相似文献