Page 199 - 48Fundamentals of Compressible Fluid Mechanics

9.7. WORKING CONDITIONS 161
16
shock . The back pressure below point c some a adjustment as to occurs with
exceptions of point d.

Mach number in Fanno Flow

4fL
¾¾
D
2
1.8
1.6
shock at
1.4
75%
50%
Mach Number 0.8 1 5%
1.2

0.6
0.4

0.2
0
0 0.05 0.1 0.15 0.2 0.25
4fL
¾¾
D
Tue Jan 4 12:11:20 2005

Fig. 9.13: The effects of pressure variations on Mach number profile as a function of
when the total resistance for Fanno Flow

9.7.2.3 Long W`XaZ [
reduction of the back pressure results in the same
up to to point c. However, point c in this case is

W`XaZ [
In the case of WYXaZ [
. In this point the exit
process as explain in the short WYXaZ [
Mach number is equal to 1 and the flow is double shock. Further reduction of the

WYXaZ [
different from point c at the case of short tube W`XaZ [
back pressure at this stage will not “move” the shock wave downstream the nozzle.
. The is no analytical solution for the location of this point c. The b
The point c or location of the shock wave is a function entrance Mach number, N
procedure is (will be) presented in later stage.
and the “extra” W`XaZ [
16 It is common misconception that the back pressure has to be at point d.