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61.
本文介绍了床面固体颗粒随水流绕过圆柱体时,将在圆柱周围的床面上形成一个无粒子运动区的试验现象。水槽试验结果表明,当固体颗粒的粒径减小时,无粒子区的范围将增大;无粒子区的范围随圆柱直径的增大而增大;水流条件的变化直接影响着床面固体颗粒的运动情况,同无粒子区的形成、消失及范围大小有密切的关系。根据试验资料,结合量纲分析,建立了无粒子区的无量纲经验关系式 相似文献
62.
S. M. Drozdov 《Fluid Dynamics》2006,41(6):857-870
The problem of formation of spatially periodic structures on the frontal surface of a cylindrically blunted body set transversely in a hypersonic flow is studied. Within the framework of the model adopted, a possible mechanism of vortex structure generation on the frontal surface of the blunt body is proposed and confirmed by calculations; in this mechanism, the curved bow shock produces a vortex flow, while in its turn the vortex, which persists under weak dissipation, acts on the shock thus maintaining its curved shape. It is shown that the spatially periodic mode of hypersonic flow past a cylinder can exist in the case of a uniform incident flow and under homogeneous boundary conditions on the body surface. 相似文献
63.
64.
65.
A. M. Lokoshchenko V. V. Nazarov 《Journal of Applied Mechanics and Technical Physics》2007,48(4):542-546
The problem of the long-term strength of an extended thick-walled tube containing a corrosive medium in the internal cavity
is solved. The diffusion of this medium into the tube material is analyzed. The diffusion equation is solved approximately
by introducing the diffusion front, and the error of the solution is estimated. The dependence of the time of fracture of
the tube on the variable tensile stress and the concentration of the medium filling the cavity is obtained.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 4, pp. 88–93, July–August, 2007. 相似文献
66.
Dr. Erik A. Toorman 《Rheologica Acta》1994,33(3):193-202
An analytical solution is presented for the calculation of the flow field in a concentric cylinder viscometer of non-ideal Bingham-fluids, described by the Worrall-Tuliani rheological model. The obtained shear rate distribution is a function of the a priori unknown rheological parameters. It is shown that by applying an iterative procedure experimental data can be processed in order to obtain the proper shear rate correction and the four rheological parameters of the Worrall-Tuliani model as well as the yield surface radius. A comparison with Krieger's correction method is made. Rheometrical data for dense cohesive sediment suspensions have been reviewed in the light of this new method. For these suspensions velocity profiles over the gap are computed and the shear layer thicknesses were found to be comparable to visual observations. It can be concluded that at low rotation speeds the actually sheared layer is too narrow to fullfill the gap width requirement for granular suspensions and slip appears to be unavoidable, even when the material is sheared within itself. The only way to obtain meaningfull measurements in a concentric cylinder viscometer at low shear rates seems to be by increasing the radii of the viscometer. Some dimensioning criteria are presented.Notation
A, B
Integration constants
-
C
Dimensionless rotation speed = µ/y
-
c
= 2µ
-
d
= 0
2–2cy
-
f()
= (–0)2+2c(–y)
-
r
Radius
-
r
b
Bob radius
-
r
c
Cup radius
-
r
y
Yield radius
-
r
0
Stationary surface radius
-
r
Rotating Stationary radius
-
Y
0
Shear rate parameter = /µ
Greek letters
Shear rate
-
= (r
y
/r
b
)2– 1
- µ
Bingham viscosity
- µ0
Initial differential viscosity
- µ
µ0-µ
-
Rotation speed
-
Angular velocity
-
Shear stress
-
b
Bob shear stress
-
B
Bingham stress
-
y
(True) yield stress
- 0
Stress parameter =
B
+µ
Y
0
-
B
-
y
相似文献
67.
Ling Guocan 《Acta Mechanica Sinica》1988,4(3):211-222
In the present paper the mechanism involved in vortex shedding flows is investigated in detail. In the early stage of the
unsteady separated flow the interaction between secondary vortices and primary vortices is quite strong. In the later stage
of the flow, corresponding to the vortex shedding the recirculating flow region on each side of the aft body goes through
such a cycle: growth-contraction-growth, the secondary separation occurs periodically rather than continuously. The reduction
of circulation is taken into account in three cases with different decay factors to study its influence on the prediction
of main flow characteristics. Results show that to simulate vortex shedding flow it is necessary to include the reduction
of circulation to bring the calculated results into good agreement with experiments. An improved discrete vortex model is
suggested in which both the secondary separation and the reduction are incorporated. The processes of vortex shedding, the
forces prediction and other flow characteristics are given and some discussions are made.
Porject is supported by National Natural Science Foundation of China. 相似文献
68.
A theoretical method for analyzing the axisymmetric plane strain elastodynamic problem of a non-homogeneous orthotropic hollow
cylinder is developed. Firstly, a new dependent variable is introduced to rewrite the governing equation, the boundary conditions
and the initial conditions. Secondly, a special function is introduced to transform the inhomogeneous boundary conditions
to homogeneous ones. By virtue of the orthogonal expansion technique, the equation with respect to the time variable is derived,
of which the solution can be obtained. The displacement solution is finally obtained, which can be degenerated in a rather
straightforward way into the solution for a homogeneous orthotropic hollow cylinder and isotropic solid cylinder as well as
that for a non-homogeneous isotropic hollow cylinder. Using the present method, integral transform can be avoided and it can
be used for hollow cylinders with arbitrary thickness and subjected to arbitrary dynamic loads. Numerical results are presented
for a non-homogeneous orthotropic hollow cylinder subjected to dynamic internal pressure.
The project supported by the National Natural Science Foundation of China (10172075 and 10002016) 相似文献
69.
Jiann-Quo Tarn 《Journal of Elasticity》2002,69(1-3):1-13
The issue of stress singularity in an elastic cylinder of cylindrically anisotropic materials is examined in the context of
generalized plane strain and generalized torsion. With a viewpoint that the singularity may be attributed to a conflicting
definition of anisotropy at r=0, we study the problem through a compound cylinder in which the outer cylinder is cylindrically anisotropic and the core
is transversely isotropic. By letting the radius of the core go to zero, the cylinder becomes one with the central axis showing
no conflict in the radial and tangential directions. Closed-form solutions are derived for the cylinder under pressure, extension,
torsion, rotation and a uniform temperature change. It is found that the stress is bounded everywhere, and singularity does
not occur if the anisotropy at r=0 is defined appropriately.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
70.