NuD = a(ReD )b ( \fracNt Af A\texttotal )c \textand f = a(ReD )b Nu_{D} = a(Re_{D} )^{b} \left( {{\frac{{N_{t} A_{f} }}{{A_{\text{total}} }}}} \right)^{c} \quad {\text{and}}\quad f = a(Re_{D} )^{b} 相似文献
6.
D. V. Sadin 《Journal of Applied Mechanics and Technical Physics》2002,43(2):286-290
The numerical modeling of wave flows of heterogeneous media with a threetemperature scheme of interphase heat and mass transfer involves the problem of equation stiffness. A discrete model of improved stability was developed to describe these processes. Test calculations of the interaction of a shock wave with a bounded layer of a mixture of a gas and droplets assuming a discrete model over a wide range of initial data showed that the stability conditions do not depend on the rate of interphase interaction (Cstability). 相似文献
7.
Dulal Pal 《Meccanica》2009,44(2):145-158
In this paper an analysis has been made to study heat and mass transfer in two-dimensional stagnation-point flow of an incompressible
viscous fluid over a stretching vertical sheet in the presence of buoyancy force and thermal radiation. The similarity solution
is used to transform the problem under consideration into a boundary value problem of nonlinear coupled ordinary differential
equations containing Prandtl number, Schmidt number and Sherwood number which are solved numerically with appropriate boundary
conditions for various values of the dimensionless parameters. Comparison of the present numerical results are found to be
in excellent with the earlier published results under limiting cases. The effects of various physical parameters on the boundary
layer velocity, temperature and concentration profiles are discussed in detail for both the cases of assisting and opposing
flows. The computed values of the skin friction coefficient, local Nusselt number and Sherwood number are discussed for various
values of physical parameters. The tabulated results show that the effect of radiation is to increase skin friction coefficient,
local Nusselt number and Sherwood number. 相似文献
8.
V. I. Zinchenko K. N. Efimov A. G. Kataev A. S. Yakimov 《Journal of Applied Mechanics and Technical Physics》2002,43(1):114-119
A study was performed of methods for controlling thermal regimes in a spatial supersonic flow around a blunt body with the simultaneous use of gas injection from the surface of the porous bluntness and heat flow in the shell material. The effect of the nonisothermicity of the shell wall on the heat and masstransfer characteristics in the boundary layer was taken into account by solution of the problem in a conjugate formulation. It is shown that heat conducting materials can be used to advantage to reduce the maximum temperatures in the screen zone. 相似文献
9.
The non-Newtonian fluid flow with a free surface occurring during the filling of a plane channel in the gravity field is modeled. The mathematical formulation of the problem using the rheological Bulkley–Herschel model is presented. A numerical finite-difference algorithm for solving this problem is developed. A parametric investigation of the main characteristics of the process as functions of the control parameters is performed. The effect of the rheological parameters of the fluid on the distribution of the quasisolid motion zones is demonstrated. 相似文献
10.
In this present work, the nonlinear response of a single-link flexible Cartesian manipulator with payload subjected to a pulsating axial load is determined. The nonlinear temporal equation of motion is derived using D’Alembert’s principle and generalised Galerkin’s method. Due to large transverse deflection of the manipulator, the equation of motion contains cubic geometric and inertial types of nonlinearities along with linear and nonlinear parametric and forced excitation terms. Method of normal forms is used to determine the approximate solution and to study the dynamic stability and bifurcations of the system. These results are found to be in good agreement with those obtained by numerically solving the temporal equation of motion. Influences of amplitude of the base excitation, mass ratio, and amplitude of static and dynamic axial load on the steady state responses of the system are investigated for three different resonance conditions. For some specific conditions, the results obtained in this work are found to be in good agreement with the previously published experimental work. The results obtained in this work will find applications in the design of flexible Cartesian manipulators with payload. 相似文献
11.
Heattransfer processes for a supersonic spatial flow around a spherically blunted cone were studied by solving direct and inverse threedimensional problems taking into account heat flow along the longitudinal and circumferential coordinates. It is shown that highly heatconducting materials can be used to advantage to decrease the maximum temperatures on the windward side of streamline bodies. 相似文献
12.
The boundaryvalue problem of waves on the surface of a twophase medium with a nonuniform (exponential) distribution of the disperse phase is formulated. An asymptotic solution of the linear problem in the form of damped progressive waves is obtained. The phase velocity, frequency, and damping decrement for the waves are found. The perturbation of the admixture concentration is determined, which, unlike in the case of a uniform distribution, is manifested even in a linear approximation. Numerical calculations were performed for concrete media. 相似文献
13.
14.
This paper presents the bifurcation behaviors of a modified railway wheelset model to explore its instability mechanisms of hunting motion. Equivalent conicity data measured from China high-speed railway vehicle are used to modify the wheelset model. Firstly, the relationships between longitudinal stiffness, lateral stiffness, equivalent conicity and critical speed are taken into account by calculating the real parts of the eigenvalues of the Jacobian matrix and Hurwitz criterion for the corresponding linear model. Secondly, measured equivalent conicity data are fitted by a nonlinear function of the lateral displacement rather than are considered as a constant as usual. Nonlinear wheel–rail force function is used to describe the wheel–rail contact force. Based on these modifications, a modified railway wheelset model with nonlinear equivalent conicity and wheel–rail force is set up, and then, some instability mechanisms of China high-speed train vehicle are investigated based on Hopf bifurcation, fold (limit point) bifurcation of cycles, cusp bifurcation of cycles, Neimark–Sacker bifurcation of cycles and 1:1 resonance. In particular, fold bifurcation of cycles can produce a vast effect on the hunting motion of the modified wheelset model. One of the main reasons leading to hunting motion is due to the fold bifurcation structure of cycles, in which stable limit cycles and unstable limit cycles may coincide, and multiple nested limit cycles appear on a side of fold bifurcation curve of cycles. Unstable hunting motion mainly depends on the coexistence of equilibria and limit cycles and their positions; if the most outward limit cycle is stable, then the motion of high-speed vehicle should be safe in a reasonable range. Otherwise, if the initial values are chosen near the most outward unstable limit cycle or the system is perturbed by noises, the high-speed vehicle will take place unstable hunting motion and even lead to serious train derailment events. Therefore, in order to control hunting motions, it may be the easiest way in theory to guarantee the coexistence of the inner stable equilibrium and the most outward stable limit cycle in a wheelset system. 相似文献15.
Christiaan le Roux 《Archive for Rational Mechanics and Analysis》1999,148(4):309-356
. This paper treats the solvability of the equations of motion for an incompressible fluid of grade two subject to nonlinear
partial slip boundary conditions in a bounded simply‐connected domain. The existence of a unique classical solution, global
in time, is proved under suitable regularity and growth restrictions on the initial data, the slip law and the body and surface
forces. The method is based on a fixed-point formulation of the problem.
(Accepted October 5, 1998) 相似文献
16.
Nonlinear Dynamics - In this paper, the general kinematics and dynamics of a rigid body is analysed, which is in contact with two rigid surfaces in the presence of dry friction. Due to the rolling... 相似文献
17.
Ikue Itamoto Hideshi Ishida Masahiko Higashiyama Daigo Miki Genta Kawahara 《Heat and Mass Transfer》2009,46(2):153-165
In this study surface-averaged and extremal properties of heat transfer and shear stress on the upper wall surface of Rayleigh–Bénard
convection are numerically examined. The Prandtl number was raised up to 103, and the Rayleigh number was changed between 104 and 107. As a result, average Nusselt number Nu and shear rate τ/Pr depends on Pr, Ra, and the entire numerical results are distributed between two correlation equations corresponding to small and large Pr. The small and large Pr equations are closely related to steady and unsteady flow regimes, respectively. Nevertheless, a single relation τ/Pr ~ Nu
3.0 exists to explain the entire results. Similarly the change of local maximal properties Nu
max and τ
max/Pr depends on Pr, Ra, and these values are also distributed between two correlation equations corresponding to small and large Pr cases. Despite such complicated dependence we can obtain a correlation equation as a form of τ
max/Pr ~ Nu
max2.6, which has not been obtained theoretically. 相似文献
18.
N. P. Plakhtienko 《International Applied Mechanics》2010,46(4):461-466
A refined mathematical dynamic model of a rigid body with a gravity–friction seismic damper moving inside a movable hemispherical
rough depression is set up. This model describe the frequency and decrement properties of a rigid body undergoing translational
vibrations on a gravity–friction seismic-isolation mechanism. The mechanism consists of two platforms. The lower (supporting)
platform has spherical supports that contact with the upper (supported) platform within its hemispherical depressions. The
equations of motion incorporate the nonideality of the unilateral constraints and the shock interaction of a material point
with the sphere. It is shown how to join the models describing the free motion and the sliding motion of the point over a
spherical surface 相似文献
19.
B. L. Kantsyrev 《Journal of Applied Mechanics and Technical Physics》2004,45(1):31-36
The effect of the fluctuating components of kinetic energy and stress tensor of the carrier phase, which were previously obtained by the cell technique, on the properties of the system of equations of a gas–liquid flow with incompressible phases is considered. It is shown that the characteristic properties of this system and also the possibility of modeling the Zuber–Findlay empirical relation are determined by the tensor of fluctuating stresses of the carrier phase. 相似文献
20.
The condensation heat transfer characteristics for CO2 flowing in a horizontal microfin tube were investigated by experiment with respect to condensation temperature and mass flux. The test section consists of a 2,400?mm long horizontal copper tube of 4.6?mm inner diameter. The experiments were conducted at refrigerant mass flux of 400–800?kg/m2s, and saturation temperature of 20–30?°C. The main experimental results showed that annular flow was highly dominated the majority of condensation flow in the horizontal microfin tube. The condensation heat transfer coefficient increases with decreasing saturation temperature and increasing mass flux. The experimental data were compared against previous heat transfer correlations. Most correlations failed to predict the experimental data. However, the correlation by Cavallini et al. showed relatively good agreement with experimental data in the microfin tube. Therefore, a new condensation heat transfer correlation is proposed with mean and average deviations of 3.14 and ?7.6?%, respectively. 相似文献
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