Digital Signal Processing Reference
In-Depth Information
2
Defining the Equation in Order to Obtain the Value of
Viscosity Coefficent
η
The viscosity coefficient
at room temperature is determined by Stokes's law
F
=
3
πη
vd
(1)
v
where is the sphere's diameter, is the constant velocity of falling after equili-
brium among the gravitational
、
buoyancy and viscous force are established.
d
F
is
the viscosity force in liquid , determined by.
1
′
3
′
(2)
Fmg gV dg
=−
ρ
=
π
(
ρρ
−
)
6
m
Where
、
and are the sphere's density, volume, and mass in air, respec-
tively, and the density of liquid[1].
By replacing
ρ
V
ρ
′
F
3
πη
vd
lt
v
with
in the equation (2), Let
be
, one one
obtains
.
(
ρρ
−
′
)
gd t
2
η
=
(3)
18
l
Stokes's law requires the sphere to fall in the liquid with infinite width and extensive,
but the diameter and the depth of the vessel are always finite, so the actual velocity
should multiply an amending coefficient
12.1
d
D
D
(
is the inner diameter of the
+
vessel). Thus, the expression of calculating the coefficient of the viscosity can be
written as.
′
2
(
ρρ
−
)
gd t
d
η
=
(4)
18 (1
l
+
2.1
)
D
l
t
Where and are the distance and time of sphere falling after equilibrium among
the gravitational
、
buoyancy and viscous force are established.
3
Computer Software
Flash is a popular software, and can be downloaded freely from the Internet [6].
Compared with the programs written in Delphi or C++, Flash has the advantages of
easy-using, freely cost and work under Windows operating system which is in com-
mon use.
Flash has the function of editing *.avi format digital video, which can help to
measure the time and distance.
