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Table 2.6 Length, velocity, and time scales of environmental fluid processes and systems
Time scale
Velocity
scale
Vertical
length scale
Horizontal
length scale
Process
Micro turbulence Few
seconds
1–10 cm/s 1–10 cm
1–10 cm
Shear turbulence Few
minutes
0.1–1 m/s
0.1–10 cm
0.1–10 m
Water waves
Seconds to
minutes
1–10 m/s
1–100 cm
0.1–10 m
Convection
Hours/days/
seasons
0.1–1 m/s
1–1000 m
10–1000 m
Atmospheric
systems
Urban airshed
Hours
1–10 m/s
100–1000 m 1–10 km
Sea breeze
Hours
1–10 m/s
100–1000 m 1–10 km
Thunderstorms
Hours
1–10 m/s
100–5000 m 1–10 km
Mountain waves Days
1–10 m/s
10–1000 m
1–10 km
Tornado
Minutes to
hours
1–10 m/s
100–1000 m 1–10 km
Water systems Watershed
Hours to
days
1–10 m/s
1–10 m
1–10,000 km
Aquifers
Seasons to
decades
1–10 m/s
10–1000 m
1–1000 km
Wetlands
Days to
seasons
1–10 m/s
1–10 m
10–1000 m
Small streams
Seconds to
minutes
1–10 m/s
0.1–1 m
1–10 m
Major river
Days to
seasons
1–100 cm/s 1–10 m
10–1000 m
Lakes
Hours to
days
1–10 m/s
10–1000 m
1–100 km
Estuaries
Hours
0.1–1 m/s
1–10 m
1–10 km
Coastal ocean
Few days
0.1–1 m/s
1–100 m
1–100 km
Upper ocean
Weeks to
decades
1–100 cm/s 100–1000 m 10–1000 km
Abyssal ocean
Decades
and beyond
0.1–1 cm/s Basin depth
Global
Body system
Human
circulatory system
Seconds to
minutes
0.3–40 cm/s Few
centimeters
Few
centimeters
Human
respiratory system
Seconds to
minutes
0.4–1.4 m/s Few
centimeters
Few
centimeters
Source: Cushman-Roisin et al. (2018); Tang et al. (2013); Wikipedia (2018)
2.4 Fluid Mechanics