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1.
Inrecentyears,applicationsofquaternionmatricesarebecomingmoreandmoreimportantandextensiveinrigidmechanics,quantummechanics,controltheoryandhelicaltechnology[1~3].Withtherapiddevelopmentoftheabovedisciplines,itisgettingmoreandmorenecessaryforustofurth… 相似文献
2.
蔡树棠 《应用数学和力学(英文版)》1983,4(5):681-697
In this article, as the velocity gradient is taken as a constant value, we obtain the solutions of the equation of fluctuation
velocity after Fourier transform. When the mean velocity gradient is small, they represent the picture of eddies, of which
the homogeneous turbulence (both isotropic and nonisotropic) of the final period is composed. By using the eddies of these
types at different times, we may compose the steady turbulent field with the constant velocity gradient and this field may
represent the turbulent field in the central part of the channel flow or pipe flow approximately. Then we may obtain the double
velocity correlation function of this turbulent field, which involves both longitudinal correlation coefficient
and the transversal correlation coefficient
. We compare these theoretical coefficients with the experimental data of these coefficients at initial period and final period
of isotropic homogeneous turbulence. And then we obtain the relationship between the turbulent double velocity correlation
coefficient
and the mean velocity gradient. Finally, we get the expressions of the Reynolds stress and the eddy viscosity coefficient. 相似文献
3.
The work presented is a wind tunnel study of the near wake region behind a hemisphere immersed in three different turbulent boundary layers. In particular, the effect of different boundary layer profiles on the generation and distribution of near wake vorticity and on the mean recirculation region is examined. Visualization of the flow around a hemisphere has been undertaken, using models in a water channel, in order to obtain qualitative information concerning the wake structure.List of symbols
C
p
pressure coefficient,
-
D
diameter of hemisphere
-
n
vortex shedding frequency
-
p
pressure on model surface
-
p
0
static pressure
-
Re
Reynolds number,
-
St
Strouhal number,
-
U, V, W
local mean velocity components
-
mean freestream velocity inX direction
-
U
*
shear velocity,
-
u, v, w
velocity fluctuations inX, Y andZ directions
-
X
Cartesian coordinate in longitudinal direction
-
Y
Cartesian coordinate in lateral direction
-
Z
Cartesian coordinate in direction perpendicular to the wall
- it*
boundary layer displacement thickness,
-
diameter of model surface roughness
-
elevation angleI
-
O
boundary layer momentum thickness,
-
w
wall shearing stress
-
dynamic viscosity of fluid
-
density of fluid
-
streamfunction
- x
longitudinal component of vorticity,
- y
lateral component of vorticity,
-
z
vertical component of vorticity,
This paper was presented at the Ninth symposium on turbulence, University of Missouri-Rolla, October 1–3, 1984 相似文献
4.
In [1], by a transformation on the Lienard equation system
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5.
V. Georgescu 《Archive for Rational Mechanics and Analysis》1980,74(2):143-164
We state a particular case of one of the theorems which we shall prove. Let Ω be a bounded open set in ℝ
n
with smooth boundary and let σ=(σ
ij
)be a symmetric second-order tensor with components σ
ij
εH
k(Ω) for some (positive or negative) integer k; H
k
are Sobolev spaces on Ω. Then we have
for some u
i
εH
k
+1(Ω),i=1,...,n, if and only if
(if k<0, the integral is in fact a duality) for any symmetric tensor (ω with components
and such that
). Some applications in the theory of elasticity are also given. 相似文献
6.
A new forced convection parameter
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