Page 272 - 48Fundamentals of Compressible Fluid Mechanics

234 CHAPTER 13. OBLIQUE-SHOCK

c 7 8

4
4
4
) ) 1
"1"
The transition for shock AB is ) " -91+ + 7 8 9

c 7 8

4
4
4

),+
For the Shock BC the results are: 1 " ),+ 91"1" 7 8 "1"- )0"

c 7 8

4
4
4

) " 1 1"

"1"- 1"
1+
)
And the isentropic relationship for 7 7 8
) are

4
5
6
7

) "

9
) "
")0
90"1+

-+
+

9 -9
)
-+1+9
"
+1+1"
The combined shocks AB and BC provides the base to calculation of the total
6 8
pressure ratio at zone 3. The total pressure ratio at zone 2 is

5
7 8
: 7 8
8

(13.55)

"1"1 =),"
"-")1)
On the other hand, the pressure at 4 has to be
"1"- 1"

(13.56)

"1"
9 +
9
9
The static pressure at zone 4 and zone 3 have to match according to the govern-

ment suggestion hence, the angle for BE shock which cause this pressure ratio
needed to be found. To that, check whether the pressure at 2 is above or below or
"

above the pressure (ratio) in zone 4.
1+=), 1"

Since a weak shock must occur to increase the static pressure (see
+
Figure 5.4). The increase has to be

"1"=)1)

To achieve this kind of pressure ratio perpendicular component has to be
1+)-)
9 +
1+-)0 0"
9

.