Environmental Engineering Reference
In-Depth Information
Fig. 2.43 The relationship of reflective critical angle and pressures
fronts is perpendicular with the ground surface (Fig.
2.42
). This re
fl
ection is the
front re
ection.
Following the shock wave fronts leave the projected point; the propagation of
incident wave fronts has an angle
fl
u
1
with the ground. Now it is the oblique
re
ection. Following the increase in distance of the shock wave fronts from the
projected point, the incident angle
fl
u
1
is larger and larger while the angle between
incident shock wave fronts and re
fl
ected shock wave fronts. When
u
1
u
1c
, the
re
ected wave fronts catch and attach incident waves to form another single shock
waves
fl
composite waves. This composite waves are Mach waves.
Because the attaching of incident waves to re
—
ective waves proceeds gradually
along height, the fronts of composite waves have bigger and bigger height fol-
lowing the distance increase to explosion center. In Fig.
2.42
, the cross point of
wave fronts from the incident, re
fl
ective, and composite waves, is triple point.
The whole space above ground is divided into two parts. (1) Regular re
fl
ective
space, or close space of aerial burst. Its distance to projective point is shorter than
H
fl
u
1c
. All buildings and targets inside the space experience two shock waves:
incident and re
tg
ective space, or far space of aerial
burst. Its distance to projective point is longer than H
fl
ective waves. (2) Irregular re
fl
u
1c
. All buildings and
targets inside the space and below triple point only experience composite waves.
The propagation of air particles in the vertical direction is stagnated. So the
propagation of air particles after fronts of re
tg
fl
ective waves (including composite
waves) is horizontal. It is zero in the front re
ection. But the air particles before
fronts of composite waves are still. After composite waves pass them, the air
particles obtain propagation, which is horizontal with the ground. In theory, the
front of composite waves, or Mach rod, is perpendicular with the ground.
fl
