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961.
回转体局部空泡绕流的非线性分析 总被引:12,自引:1,他引:12
基于面元法, 通过在回转体和空泡壁面放置源汇,对回转体定长局部空泡的绕流问题进行了分析和讨论,并提出了求解回转体局部空泡绕流“正问题”的方法。计算结果表明:所给出的方法具有快速收敛的特征,第1次迭代和最终收敛时空泡壁面切向速度的误差不超过5%;随着回转体面元总数N的增加,局部空泡的空泡数σ趋于稳定;通过比较可知,该方法得到的理论估算值与实测值的一致性较好。 相似文献
962.
963.
964.
(Ca,Mg)—Sialon陶瓷在空气及水润滑条件下的磨损机理研究 总被引:7,自引:7,他引:7
利用SRV球-盘磨损试验机考察了一种(Ca,Mg)-Sialon陶瓷在空气及水中的摩擦学性能,并采用EPMA,SEM,EDAX以及XPS等分析手段对其磨损机理做了进一步研究。结果表明:(Ca,Mg)-Sialon陶瓷在水中比在空气中具有更低的摩擦因数,但具有较高的磨损体积损失。 相似文献
965.
A. V. Shenoy 《Transport in Porous Media》1993,11(3):219-241
The governing equation for Darcy-Forchheimer flow of non-Newtonian inelastic power-law fluid through porous media has been derived from first principles. Using this equation, the problem of Darcy-Forchheimer natural, forced, and mixed convection within the porous media saturated with a power-law fluid has been solved using the approximate integral method. It is observed that a similarity solution exists specifically for only the case of an isothermal vertical flat plate embedded in the porous media. The results based on the approximate method, when compared with existing exact solutions show an agreement of within a maximum error bound of 2.5%.Nomenclature
A
cross-sectional area
-
b
i
coefficient in the chosen temperature profile
-
B
1
coefficient in the profile for the dimensionless boundary layer thickness
-
C
coefficient in the modified Forchheimer term for power-law fluids
-
C
1
coefficient in the Oseen approximation which depends essentially on pore geometry
-
C
i
coefficient depending essentially on pore geometry
-
C
D
drag coefficient
-
C
t
coefficient in the expression forK
*
-
d
particle diameter (for irregular shaped particles, it is characteristic length for average-size particle)
-
f
p
resistance or drag on a single particle
-
F
R
total resistance to flow offered byN particles in the porous media
-
g
acceleration due to gravity
-
g
x
component of the acceleration due to gravity in thex-direction
-
Grashof number based on permeability for power-law fluids
-
K
intrinsic permeability of the porous media
-
K
*
modified permeability of the porous media for flow of power-law fluids
-
l
c
characteristic length
-
m
exponent in the gravity field
-
n
power-law index of the inelastic non-Newtonian fluid
-
N
total number of particles
- Nux,D,F
local Nusselt number for Darcy forced convection flow
- Nux,D-F,F
local Nusselt number for Darcy-Forchheimer forced convection flow
- Nux,D,M
local Nusselt number for Darcy mixed convection flow
- Nux,D-F,M
local Nusselt number for Darcy-Forchheimer mixed convection flow
- Nux,D,N
local Nusselt number for Darcy natural convection flow
- Nux,D-F,N
local Nusselt number for Darcy-Forchheimer natural convection flow
-
pressure
-
p
exponent in the wall temperature variation
-
Pe
c
characteristic Péclet number
-
Pe
x
local Péclet number for forced convection flow
-
Pe
x
modified local Péclet number for mixed convection flow
-
Ra
c
characteristic Rayleigh number
-
Ra
x
local Rayleigh number for Darcy natural convection flow
-
Ra
x
local Rayleigh number for Darcy-Forchheimer natural convection flow
- Re
convectional Reynolds number for power-law fluids
-
Reynolds number based on permeability for power-law fluids
-
T
temperature
-
T
e
ambient constant temperature
-
T
w,ref
constant reference wall surface temperature
-
T
w(X)
variable wall surface temperature
- T
w
temperature difference equal toT
w,ref–T
e
-
T
1
term in the Darcy-Forchheimer natural convection regime for Newtonian fluids
-
T
2
term in the Darcy-Forchheimer natural convection regime for non-Newtonian fluids (first approximation)
-
T
N
term in the Darcy/Forchheimer natural convection regime for non-Newtonian fluids (second approximation)
-
u
Darcian or superficial velocity
-
u
1
dimensionless velocity profile
-
u
e
external forced convection flow velocity
-
u
s
seepage velocity (local average velocity of flow around the particle)
-
u
w
wall slip velocity
-
U
c
M
characteristic velocity for mixed convection
-
U
c
N
characteristic velocity for natural convection
-
x, y
boundary-layer coordinates
-
x
1,y
1
dimensionless boundary layer coordinates
-
X
coefficient which is a function of flow behaviour indexn for power-law fluids
-
effective thermal diffusivity of the porous medium
-
shape factor which takes a value of/4 for spheres
-
shape factor which takes a value of/6 for spheres
-
0
expansion coefficient of the fluid
-
T
boundary-layer thickness
-
T
1
dimensionless boundary layer thickness
-
porosity of the medium
-
similarity variable
-
dimensionless temperature difference
-
coefficient which is a function of the geometry of the porous media (it takes a value of 3 for a single sphere in an infinite fluid)
-
0
viscosity of Newtonian fluid
-
*
fluid consistency of the inelastic non-Newtonian power-law fluid
-
constant equal toX(2
2–n
)/
-
density of the fluid
-
dimensionless wall temperature difference 相似文献
966.
在高速水洞中运用人工通气方法进行了航行体模型超空泡形态特性的系列实验研究.获得了不同通气流量、不同空化数和不同弗鲁德数下的空泡形态,建立了以弗鲁德数为参数的空泡几何特征参数与空化数的对应关系、空化数与通气流量系数之间的对应关系.验证了空化数是决定空泡尺度的主要无因次参数,通过改变通气流量可以有效地调控空化数,进而达到控制空泡形态的目的.文中同时给出了通气流量系数的实验曲线拟合公式,并与国外的相关实验和公式进行了比较,两者基本一致.所得结论对进一步的水下超高速航行体空泡形态控制技术研究具有参考价值. 相似文献
967.
本文提出了一种水平成层介质中弹性波粘弹性波计算的新方法,分别研究了线源和点源作用情况。该方法适用于各种粘弹性模型,数值计算简单,可模拟任意震源及所产生的各种体波、面波,数值结果表明具有很高的计算精度和计算效率。 相似文献
968.
969.
J. L. Lage
A. Bejan
J. G. Georgiadis 《International Journal of Heat and Fluid Flow》1992,13(4):408-411This note focuses on Kladias and Prasad's claim that the critical Rayleigh number for the onset of Bénard convection in an infinite horizontal porous layer increases as the Prandtl number decreases, and argues that the critical Rayleigh number (Rac) depends only on the Darcy number (Da), as linear stability analysis indicates. The two-dimensional steady-convection problem is then solved numerically to document the convection heat transfer effect of the Rayleigh number, Darcy number, Prandtl number, and porosity. The note concludes with an empirical correlation for the overall Nusselt number, which shows the effect of Prandtl number at above-critical Rayleigh numbers. The correlation is consistent with the corresponding correlation known for Bénard convection in a pure fluid. 相似文献
970.
In the present paper we consider interior and exterior mixed boundary value problems of anti-plane shear in the static theory of linear piezoelectricity. Using the boundary integral equation method we reduce the problems to systems of singular integral equations with discontinuous coefficients to which the classical Nöether’s theorems on existence of the solution can be applied. This allows us to establish well-posedness results and to obtain integral solutions of the corresponding mixed boundary value problems for a rather general class of piezoelectric materials.
Mathematics Subject Classifications (2000) 45E05, 45F15, 74F15. 相似文献