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1.
The author examines nonstationary processes (combustion at varying pressure, quenching, and ignition) for a model propellant whose burning rate u and surface temperature t1 depend on pressure p and initial temperature T0. All the processes in the surface reaction zone and the gas phase are assumed inertialess. It is shown that a theory of nonstationary combustion for such a model can be constructed by analogy with the Zel'dovich theory [1, 2], in which the surface temperature of the powder is assumed fixed. The variation of burning rate with time has been investigated for small sudden pressure changes. It is shown how a sufficiently large and steep pressure drop may cause quenching of the propellant. The process of propellant ignition is subjected to a qualitative analysis.The author thanks O. I. Leipunskii, A. G. Istratov, V. B. Librovich, and A. D. Margolin for their comments and advice. 相似文献
2.
An analysis is performed to study the magnetohydrodynamic flow of an electrically conducting, viscous incompressible fluid past a semi-infinite vertical plate with variable surface temperature under the action of transversely applied magnetic field. The heat due to viscous dissipation and the induced magnetic field are assumed to be negligible. The dimensionless governing equations are unsteady, two-dimensional, coupled and non-linear governing equations. It is found that the magnetic field parameter has a retarding effect on the velocities of air and water. 相似文献
3.
Transient heat transfer from a continuous moving flat surface with varying wall temperature is studied. Numerical results are presented for the transient temperature profiles and heat transfer rates from the wall for Prandtl numbers varying from 0.01 to 1000. Asymptotic solutions for steady state heat transfer rates for large Prandtl number are also presented. 相似文献
4.
Effect of variable viscosity on boundary layer flow along a continuously moving plate with variable surface temperature 总被引:1,自引:0,他引:1
Flow of an incompressible viscous fluid past a continuously moving semi-infinite plate is studied by taking into account variable viscosity and variable temperature. Velocity and temperature profiles are shown graphically whereas the numerical values of the skin-friction and the rate of heat transfer are listed in a table. The effect of different parameters on the flow field is discussed. 相似文献
5.
In the present study we have explored the effects of thermal buoyancy on flow of a viscoelastic second grade fluid past a
vertical, continuous stretching sheet of which the velocity and temperature distributions are assumed to vary according to
a power-law form. The governing differential equations are transformed into dimensionless form using appropriate transformations
and then solved numerically. The methods here employed are (1) the perturbation method together with the Shanks transformation,
(2) the local non-similarity method with second level of truncation and (3) the implicit finite difference method for values
of ξ ( = Gr
x
/Re
x
2, defined as local mixed convection parameter) ranging in [0, 10]. The comparison between the solutions obtained by the aforementioned
methods found in excellent agreement. Effects of the elasticity parameter λ on the skin-friction and heat transfer coefficients
have been shown graphically for the fluids having the values of the Prandtl number equal to 0.72, 7.03 and 15.0. Effects of
the viscoelastic parameter and the mixed convection parameter, ξ, on the temperature and velocity fields have also been studied.
We notice that with the increase in visco-elastic parameter λ, velocity decreases whereas temperature increases and that velocity
gradient is higher than that of temperature.
On leave of absence from the Department of Mathematics, University of Dhaka, Bangladesh. 相似文献
6.
H. P. Rani 《Heat and Mass Transfer》2003,40(1-2):67-73
A numerical study is carried out for thermal and concentration driven transient natural convection adjacent to a vertical
cylinder. The temperature and concentration level at the cylinder surface are assumed to vary as power-law type functions,
with exponents n and m respectively in the streamwise co-ordinate. The governing boundary layer equations are converted into
a non-dimensional form. A Crank-Nicolson type of implicit finite-difference method is used to solve the governing non-linear
set of equations. Numerical results are obtained and presented with various thermal and mass Grashof numbers and power law
variations. Transient effects of velocity, temperature and concentration are analyzed. Local and average skin-friction, Nusselt
number and Sherwood number are shown graphically. 相似文献
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8.
Viscous dissipative fluid flow past a semi‐infinite vertical plate with variable surface temperature
G. Palani 《国际流体数值方法杂志》2007,55(12):1157-1169
An analysis of the effect of viscous dissipative heat on two‐dimensional viscous incompressible fluid flow past a semi‐infinite vertical plate with variable surface temperature is carried out. The dimensionless governing equations are unsteady, two‐dimensional, coupled, and non‐linear governing equations. A most accurate, unconditionally stable and fast converging implicit finite‐difference scheme is used to solve the non‐dimensional governing equations. Velocity and temperature of the flow have been presented graphically for various parameters occurring in the problem. The local and average skin friction and Nusselt number are also shown graphically. It is observed that greater viscous dissipative heat causes a rise in the temperature. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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The steady nonlinear hydromagnetic flow of an incompressible, viscous and electrically conducting fluid with heat transfer over a surface of variable temperature stretching with a power-law velocity in the presence of variable transverse magnetic field is analysed. Utilizing similarity transformation, governing nonlinear partial differential equations are transformed to nonlinear ordinary differential equations and they are numerically solved using fourth-order Runge–Kutta shooting method. Numerical solutions are illustrated graphically by means of graphs. The effects of magnetic field, stretching parameter and Prandtl number on velocity, skin friction, temperature distribution and rate of heat transfer are discussed. 相似文献
11.
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
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13.
Michael A. Marr James S. Wallace Sanjeev Chandra Larry Pershin Javad Mostaghimi 《Experimental Thermal and Fluid Science》2010,34(2):183-189
A fast response thermocouple was developed for measuring surface temperatures of aluminum components in ICE combustion chambers. The key features of the design are the use of the aluminum substrate as one of the thermocouple metals and the use of a thick copper layer as the hot junction at the surface. The copper equalizes the hot junction temperature with the surrounding aluminum to correct for the differences in thermal properties between the two materials. FEA determined the optimum thickness of the copper layer to be between 100 and 125 μm. Under typical SI engine heat flux conditions, the thermocouple should be able to measure average surface temperatures within 0.19 °C and the magnitude of temperature swings within 6% of true values.Following the FEA, the optimized thermocouple was tested in a SI engine. Experimental results displayed the same trends as the FEA at measuring average temperatures and temperature swings, suggesting the thermocouple was performing as predicted. 相似文献
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15.
Finite-difference solution of the transient natural convection flow of an incompressible viscous fluid past an impulsively
started semi-infinite vertical plate with variable surface temperature and mass flux is presented here. The Velocity profiles
are compared with exact solution and are found to be in good agreement. The steady-state velocity, temperature and concentration
profiles are shown graphically. It is observed that there is a rise in the velocity due to the presence of a mass diffusion.
The local as well as average skin-friction, Nusselt number and Sherwood number are shown graphically.
Received on 27 May 1998 相似文献
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M. Sc. J. R. Zhuang Dr. K. Werner Prof. Dr.-Ing. E. -U. Schlünder 《Heat and Mass Transfer》1995,30(3):183-186
In many practical cases, one heats a semi-infinite solid with a constant heat flux source. For such an unsteady heat transfer problem, if the body has a uniform initial temperature, the analytical solution has been given by Carslaw and Jaeger. The surface temperature of the semi-infinite body follows the $\sqrt t $ -rule, that is, the surface temperature changes in proportion to square root of heating time. But if, instead of the uniform initial temperature, the body has a temperature distribution at the beginning of heating, the analytical solution has not yet been developed. Analytical solutions to the same problem with an exponential or a linear initial temperature distribution are obtained in this paper. It is shown, that in the case of a linear initial temperature distribution the surface temperature also changes according to $\sqrt t $ -rule Approximating the initial temperature distribution near the surface by its tangent at the surface, it is found that the surface temperature within a short time after the start of heating should also satisfy the $\sqrt t $ -rule, in spite of an arbitrary initial temperature distribution. The experimental data support this argument. Furthermore, the constant heat flux can be calculated after relationship between the surface temperature and heating time according to the equation derived in this paper, if the initial temperature distribution or its first-order derivative at the surface is known. 相似文献
18.
A simple endochronic transient creep model of metals with applications to variable temperature creep
《International Journal of Plasticity》1996,12(2):239-253
Similar to the theory of endochronic plasticity, modified by Valanis in 1980, a simple endochronic transient creep model of metals is proposed by using a definition of intrinsic time ζ, measured within the creep strain tensor space, whose metric tensor is treated as a simple power form of creep strain-rate sensitive material function. The resulting constitutive equation of creep (Endocreep) contains only three material constants whose values can be determined completely by a simple creep test. An incremental form involving isothermally constant creep stress, with or without jump, and constant stress with temperature jump, are then formulated.In the applications of Endocreep on 304SS under variable temperature creep, data of simple creep tests, provided by Ohashi et al. at 650°C, Ohno et al. at 600°C, Findley and Cho at 593°C–649°C, are employed to determine material constants. The computational results in the simulation of creep tests under step-up and step-down temperature with constant axial stress are found in very good agreement with data provided by Findley and Cho. However, the results reveal that the model is too simple to deal with the recovery response of unloading. Beside this deficiency the model and its computational method proposed have a potential in the future FEM creep analysis of general thermomechanical loading history. 相似文献
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The present note considers two problems concerning the thermocapillary motion, due to the existence of a temperature gradient,
of a weightless liquid with a parabolic dependence of the surface tension on the temperature. These problems admit self-similar
solutions (in the generalized sense) within the framework of the Navier-Stokes equations. It is noted that the solution may
not be unique.
Moscow. Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 132–137, September–October, 1988. 相似文献