Separation line
y
u
z
R
ω
Mean horseshoe
vortex axis
u
u
u
x
u
u
Fig. 5.9 Schematic of air circulation where the mean flow is oriented perpendicular to a
hemispherical building (after Rohatgi and Nelson 1994)
High turbulence
5 h s
17%
20%
6%
5%
S p e e d d e c r e a s e
T u r b u le n c e in c r e a s e
10 h s
20 h s
15 h s
Fig. 5.10 Schematic of air circulation regime when the mean flow is oriented perpendicular to a
prismatic building with two symmetrical sloping roofs (after Rohatgi and Nelson 1994)
5.4 Flow in Urban Areas
145
y
u
z
R
ω
Mean horseshoe
vortex axis
u
u
u
x
u
u
Fig. 5.9 Schematic of air circulation where the mean flow is oriented perpendicular to a
hemispherical building (after Rohatgi and Nelson 1994)
High turbulence
5 h s
17%
20%
6%
5%
S p e e d d e c r e a s e
T u r b u le n c e in c r e a s e
10 h s
20 h s
15 h s
Fig. 5.10 Schematic of air circulation regime when the mean flow is oriented perpendicular to a
prismatic building with two symmetrical sloping roofs (after Rohatgi and Nelson 1994)
5.4 Flow in Urban Areas
145