Page 268 - 48Fundamentals of Compressible Fluid Mechanics

230 CHAPTER 13. OBLIQUE-SHOCK

θ

δ

Fig. 13.15: Oblique shock occurs around a cone. This photo is courtesy of Dr. Grigory
Toker a Research Professor at Cuernavaco University at Mexico. According to
his measurement the cone half angle is and the Mach number is 2.2.

c 7 8
4

4
4
"1"
1 =) =)

9
)

91+-9

Because the flow is around Cone it must be a weak shock. Even if the cone

was a wedge, the shock will be weak because the maximum (transition to a strong
. Note that Mach number is larger than the predicted by

7 8
the wedge.
shock) occurs at about +
13.4.12 Application of oblique shock
One of the practical application of the oblique shock is the design of inlet suction
for supersonic flow. It is suggested that series of weak shocks should replace one
25
normal shock to increase the efficiency (see Figure 13.17) .
Clearly with a proper design, the !#"
flow can be brought to a subsonic flow

'&(
just below . In such case there is $&%
less entropy production (less pressure
loss.). To illustrate the design signifi-
cance of the oblique shock the following
example is provided.
Fig. 13.17: Two variations of inlet suction for
supersonic flow
25 In fact, there is a general proof that regardless to the equation of state (any kind of gas) the entropy
is be minimized through a series of oblique shocks rather than a single normal shock. See for details
in Henderson and Menikoff ”Triple Shock Entropy Theorem,” Journal of Fluid Mechanics 366 (1998) pp.
179–210.