Environmental Engineering Reference
In-Depth Information
2.5
2.0
1.5
1.0
0.5
0.0
-5
5
15
25
35
Temperature (
0
C)
FIGURE 2.5
Viscosity as a function of temperature. Note that viscosity doubles when tem-
perature drops from 30 to 0°C (i.e., a range of temperatures across seasons in temperate sur-
face water) (after Weast, 1978).
isms swim (a bacterium with a cell length of 1
m experiences viscous
forces in water similar to a human swimming in tar), (iii) when natural se-
lection favors streamlined organisms, (iv) how quickly particles settle in
water, and (v) how fast groundwater flows. For example, when ground-
water is moving through two sediment types that have the same surface
area of flow channels but one has more 1-
m diameter pores and the other
has fewer pores of 5-
m diameter, the water flows much more slowly
through the sediment with the 1-
m pore diameter holes. The flow is lower
Salmon
Salmon
B
10
7
A
10
4
Copepod
Copepod
Mayfly larva
Mayfly larva
10
1
Unicellular alga
Unicellular alga
10
-2
Bacterium
Bacterium
10
-5
10
-7
10
-5
10
-3
10
-1
10
1
10
-6
10
-4
10
-2
10
0
10
2
Velocity (m s
-1
)
Size (m)
FIGURE 2.6
Reynolds number as a function of size (A) and velocity (B) for a variety of
aquatic organisms. Note the log scales (data from Vogel, 1994).
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