Page 277 - 48Fundamentals of Compressible Fluid Mechanics

13.4. SOLUTION OF MACH ANGLE 239

Example 13.12:
Compare a direct normal shock to oblique shock with a normal shock. Where will
be total pressure loss (entropy) larger? Assume that upstream Mach number is 5
. What is the deflection angle in
this case?
and the first oblique shock has Mach angle of
SOLUTION
For the normal shock the results are

5
4
4

9
9
While the results for the oblique shock are 9 6 6 " 7 7 78 78 + )
9
5

c 7 8

4
4
4

9
"1"
And the additional information is 91 ) 7 8
9

c 7 5 7 8 7 8

4
4
) 1+
9
+ =)09
"1"

The normal shock that follows this oblique is 7 9 5
90

5

4
4
78

7
6

78
7
9
1+
90
) 9
+=)
=)
+- -91

The pressure ratios of the oblique shock with normal shock is the total shock in the
second case. =) ) -+
6

5

+ )19#
+ )09
+- -91
Note the static pressure raised less the combination shocks compare the the nor-

. .
mal shock but the total pressure has the opposite results.
9

. .
Example 13.13:
A flow in tunnel end up with two deflection angles from both sides (see the following
Figure).