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排序方式: 共有3498条查询结果,搜索用时 921 毫秒
51.
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
52.
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
53.
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
54.
M. Yu. Plotnikov A. K. Rebrov 《Journal of Applied Mechanics and Technical Physics》2005,46(5):658-663
A supersonic flow of a binary mixture of gases in a wide range of rarefaction (from a flow with a Knudsen number K
n
= 0.1 to a free-molecular flow) around a cylinder is studied by means of direct statistical Monte Carlo simulations (DSMC method). The influence of a small fraction of heavy particles in a light gas flow on the region of significant nonequilibrium near the cylinder and on the heat flux is considered.__________Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 5, pp. 53–59, September–October, 2005. 相似文献
55.
56.
配点类无网格法需要计算近似函数的二阶导数,因而在移动最小二乘(MLS)近似中至少要采用二次基函数。本文利用Voronoi图对双重点移动最小二乘近似法进行了改进,建立了基于Voronoi图的双重点移动最小二乘近似(VDG),并利用加权最小二乘法离散微分方程,导出了双重点最小二乘配点无网格法(MD GLS)。该方法将求解域用节点离散,并以节点为生成点建立Voronoi图,取Voronoi多边形的顶点为辅助点。近似函数及其二阶导数的计算过程可分解为两个步骤:首先用场函数节点值拟合辅助点处近似函数的一阶导数,再以辅助点处近似函数的一阶导数值拟合节点处近似函数的二阶导数。由于在每一步中只需计算MLS形函数及其一阶导数,这种近似方法需要较少的影响点和较小的影响域。同时借助于Voronoi结构的优良几何性质,可以快速地搜索影响点。研究表明,与基于MLS的加权最小二乘无网格法(MWLS)相比,这种方法可以显著提高计算效率,并且在精度和收敛性方面也有所改善。 相似文献
57.
A finite element analysis of the flange earrings of strong anisotropic sheet metals in deep-drawing processes 总被引:1,自引:0,他引:1
Flange earrings of strong anisotropic sheet metals in deep-drawing process are numerically analyzed by the elastic-plastic
large deformation finite element formulation based on a discrete Kirchhoff triangle plate shell element model. A Barlat-Lian
anisotropic yield function and a quasi-flow corner theory are used in the present formulation. The numerical results are compared
with the experimental ones of cylindrical cup drawing process. The focus of the present researches is on the numerical analysis
and the constraining scheme of the flange earring of circular sheets with strong anisotropy in square cup drawing process.
The project supported by the National Natural Science Foundation of China (19832020) and Provincial Natural Science Foundation
of Jilin, China (200000519) 相似文献
58.
Michael C. Mackey Irina G. Nechaeva 《Journal of Dynamics and Differential Equations》1994,6(3):395-426
We study the stability of linear stochastic differential delay equations in the presence of additive or multiplicative white and colored noise. Using a stochastic analog of the second Liapunov method, sufficient conditions for mean square and stochastic stability are derived. 相似文献
59.
周向导波在空心圆柱体中传播的数值模拟研究 总被引:1,自引:0,他引:1
在石油、化工、食品和城市供水等行业,由于腐蚀等原因而引起泄漏事故,造成巨大的经济损失和资源浪费.因此,能够预先检测到管道缺陷避免事故发生显得十分重要.基于弹性动力学理论,利用Matlab编程实现周向导波在空心圆柱体中传播的数值模拟.利用特征函数展开法计算出周向导波的频散曲线及0.6MHz和1MHz各个模态的时域波形图并据此分析激励方式同周向导波传播的关系,频率为1MHz或0.6MHz时,1和2模态在空心圆柱壳中传播的周向导波中处于主导地位:各模态的径向或周向位移幅度会受到激励入射角的影响而变化并且周向导波的位移幅度随着激励入射角的增加而增加:得到特定频率下,周向导波各模态径向、周向位移的变化关系.本文结果为进一步利用实验方法研究周向导波在空心圆柱体中传播特性和缺陷检测奠定了基础. 相似文献
60.