Biomedical Engineering Reference
In-Depth Information
0.15
0.1
0.05
0
0
0.2
0.4
0.6
0.8
1
(
r/R
)
2
FIGURE 10.3
Shear stress uniformity obtained for three different devices. Dotted line: micro-
cosm of Gust (1990) (Reynolds number is 68672); dashed line: shear inducer
device with flat conical sides (Sun and Lee 2005) (cone-substrate distance
h
= 100
m, cone angle
α
=1
◦
, angular velocity
ω
= 10 rpm; solid line: multi-
ring device of (Khalili and Javadi 2009) compared with the microcosm; bold
solid line: multiring device miniaturized version.
µ
as the differential pressure is concerned, the multiring device has a better
performance.
10.3.2 Tortuosity of Marine Sediments
Permeability and porosity are two important physical properties of any seabed
sediment or, in general, any porous media. Beside these two properties, there
exists a third quantity known as tortuosity, which significantly influences the
ongoing exchange processes in the field of marine geochemistry and geophysics.
From hydrodynamic point of view, the tortuosity can be defined as follows:
If a fluid particle located in the upstream can migrate on a purely horizontal
path to a point downstream within a flow domain, then the tortuosity of the
path would be
T
=
l/L
= 1 with
l
and
L
being the path-line length and the
geometry length in the flow direction. Hence, the more tortuous the path-line
of the fluid particle within a porous medium (because of the existence of solid
obstacles) becomes, the larger is
T
(see Figure 10.5).
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