Page 270 - 48Fundamentals of Compressible Fluid Mechanics

232 CHAPTER 13. OBLIQUE-SHOCK

neglect
the detached
distance
!#"
7 ◦
2 Normal shock

1 3 4
7 ◦
$&%
Fig. 13.18: Schematic for example 13.4

c 7 5 5 7 8 7 8

4
4
) "- 1+
)
9
"1"
9
"1
with new upstream Mach number of
"
results in )

In the new region new angle is )

7

) "-

c 7 8

4
4
4

) "-
) )0+
And the additional information is + ),+ "1 9 9-9 " 7 8 "1+9

c 7 7 5 7 8

4
4
7 8
) "-
)
"
)-)
"1"9
+ +
9 -
A oblique shock is not possible and normal shock occurs. In such case, the
-9
results are: 4 4 5

5

7 8
7
6

7 8
+

")
With two weak shock waves and a normal shock the total pressure loss is
+
+

"1 -"

6
7
5

The static pressure ratio for the second case is "1" 9 " "1+

.
"- 1" #
"1+9

.

-9
+
)
+
The loss in this case is much less than in direct normal shock. In fact, the

loss in the normal shock is 31% larger for the total pressure.
.
+
+ +

.