Environmental Engineering Reference
In-Depth Information
“
II
”
means the zone with re
fl
ected shock waves passing through. q
1
and q
2
are
fl
ow
rates of air in
zones separately.
After passing the shock wave fronts, both the velocity/rate and direction of air
change. The tangential component parallel to shock wave fronts remains constant,
and the normal component becomes smaller. So the direction of
“
I
”
and
“
II
”
fl
ow turns toward
the wall/surface. Below equation is obtained from Fig.
2.41
.
u
1
¼
q
1
cos
ð
u
1
h
Þ
q
0
cos
In the two sides of incident wave fronts, both energy and momentum are
conserved.
q
0
q
0
sin
u
1
¼
q
1
q
1
sin
ð
u
1
h
Þ
P
0
þ q
0
q
0
sin
2
u
0
¼
q
1
q
1
sin
2
ð
u
1
h
Þ
P
1
Likewise, the incident
fl
flow in
“
I
”
zone is q
1
.Itin
fl
ows
“
II
”
zone with an angle of
u
2
þ h
from the fronts OR of re
fl
ected waves. Because of the impact of velocity
component q
1
cos
ow q
2
directs outward and it is parallel
with the rigid surface. For the two sides of re
ð
u
2
þ h
Þ
, the re
fl
ected
fl
fl
ected waves, below equations are
established.
q
2
cos
u
2
¼ q
1
cos
ð
u
2
þ h
Þ
q
2
q
2
sin
u
2
¼
q
1
q
1
sin
ð
u
1
þ h
Þ
q
2
q
2
sin
2
u
2
þ
P
2
¼
q
1
q
1
sin
2
ð
u
2
þ h
Þ
P
1
The impact adiabatic function of incident waves and re
fl
ected waves are
q
1
ð
k
þ
1
Þ
P
1
þ
k
ð
1
Þ
P
0
q
0
¼
ð
k
1
Þ
P
1
þ
k
þ
ð
1
Þ
P
0
and
q
2
q
1
¼
ð
k
þ
1
Þ
P
2
þ
k
ð
1
Þ
P
1
ð
k
1
Þ
P
2
þ
k
þ
ð
1
Þ
P
1
are obtainable from above equations. The calculation
process is very complex. As a matter of convenience, the oblique re
P
2
; q
2
; u
2
;
q
1
and
ʸ
fl
ection is
simpli
ed to Eq.
2.100
.
6
D
P
1
D
P
1
þ
7P
0
cos
2
D
P
2
¼
ð
1
þ
cos
u
Þ
D
P
1
þ
u
1
ð
2
:
100
Þ