NAVWEPS 00-8OT-80 
HIGH SPEED AERODYNAMICS 
TABLE 3-P. Suprnonk Wave Charactwiltks 
Type of wave formation 
Flow direction change. 
Efkct cm velociry and Mach 
number. 
Effect on static pressure and 
density. 
_- 
Oblique shock wave 
“Flow into a corner,” 
turned into preceding 
flow. 
Decreased but still supcr- 
sonic. 
Increase. :. 
DKICaSe 
_- 
__ 
__ 
__ 
- 
Normal shock wave. 
No change. 
Great increase, 
Great decrease 
- 
__ 
-. 
-. 
-. 
- 
Expansion wwc. 
‘/ // 
< 
- ,/$y 
“Flow around a corner,” 
turned away from pre- 
ceding flow. 
Increased to higher super- 
sonic. 
DeCrWSe. 
No change (no shock). 
SECTIONS IN SUPERSONIC FLOW 
In order to appreciate the effect of these 
various wave forms on the aerodynamic char- 
acteristics in supersonic flow, inspect figure 3.8. 
Parts (a) and (b) show the wave pattern and 
resulting pressure distribution for a thin flat 
plate at a positive angle of attack. The air- 
stream moving over the upper surface passes 
through an expansion wave at the leading edge 
and then an oblique shock wave at the trailing 
edge. Thus, a uniform suction pressure exists 
over the upper surface. The airstream moving 
underneath the flat plate passes through an 
oblique shock wave at the leading edge then an 
expansion wave at the trailing edge. This pro- 
duces a uniform positive pressure on the under- 
side of the section. This distribution of pres- 
sure on the surface will produce a net lift and 
incur a subsequent drag due co lift from the in- 
clination of the resultant lift from a perpen- 
dicular co the free stream. 
Parts (c) and (d) of figure 3.8 show the 
wave pattern and resulting pressure distribu- 
tion for a double wedge airfoil at zero lift. 
The airstream moving over the surface passes 
through an oblique shock, an expansion wave, 
and another oblique shock. The resulting 
pressure distribution on the surfaces produces 
no net lift, but the increased pressure on the 
forward half of the chord along with the de- 
creased pressure on the aft half of the chord 
produces a “wave” drag. This wave drag is 
caused by the components of pressure forces 
which are parallel to the free scream direction. 
The wave drag is in addition to the drag due 
to friction, separatien, lift, etc., and can be 
a very considerable part of the total drag at 
high supersonic speeds. 
Parts (e) and (f) of figure 3.8 illustrate the 
wave pattern and resulting pressure distribu- 
tion for the double wedge airfoil at a small 
positive angle of attack. The net pressure 
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