Environmental Engineering Reference
In-Depth Information
where
F
E
is the fraction evaporated;
T
s
is the sea temperature;
T
0
,
T
G
,
A
, and
B
are constants derived from distillation data;
K
a
is the mass transfer coefficient for
evaporation;
h
is the slick thickness.
Emulsification is the process of the formation of water-in-oil emulsions changing
the properties and characteristics of oil to a large degree. The rate of water incor-
poration increases as the water content in emulsion increases, so it is usually to
character the emulsification degree. Most models that incorporate the phenomenon
use an equation proposed by [
8
].
K
b
1
exp
−
2
t
10
−
6
K
b
2
×
Y
w
=
−
(
1
+
W
)
,
(6.10)
where
Y
w
is the fractional water content;
K
b
is mousse viscosity constant.
Although it is considered that oil spilled on the sea surface will go much faster
into evaporation than solution, the soluble oil components (in particular the aromatic
compounds) can bring disaster to biologic life form a toxicological point of view. In
this oil spill model, the mass of soluble is negligible compared to the dispersed oil
droplet near the surface but of the same order of magnitude in the deeper water. The
rate of dissolution is written as
D
t
=
K
d
A
S
D
,
(6.11)
where
D
t
is the total dissolution rate of the oil slick;
K
d
is a dissolution mass transfer
coefficient;
A
S
is the slick area;
D
is the oil solubility in water.
An oil slickmay deposit or re-enter into the sea after reaching a shoreline. There are
several factors affecting the result, including oil properties, shoreline types, onshore
currents driven by wind stress and tidal currents. A model incorporating all these
factors is almost impossible due to limited data available. So far, the simulation of the
oil-shoreline interaction is primarily through empirical formulation because complex
processes and limited available data. A parameter oil-holding capacity, which means
howmuch oil will retain per unit area on a given type shoreline, is defined to quantify
the interaction of oil with the shoreline. Once the shoreline oil-holding capacity is
reached, oil will undergo longshore transport processes. Based on Humphreys study,
the maximum beach capacity for oil can be expressed as
Q
max
=
L
s
W
s
D
s
ʷ
eff
,
(6.12)
where
Q
max
is maximum capacity of a beach for oil;
L
s
,
W
s
and
D
s
are respectively
length, width, and depth of sediments on the beach; and
ʷ
eff
is effective porosity of
the sediments on the beach (0.12-0.46).
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