Page 147 - 48Fundamentals of Compressible Fluid Mechanics

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It should be noted that the flow rate is constant and maximum for any point beyond
the point ”a” even if the shock is exist. The flow rate is expressed as following

The temperature and pressure at the throat are:

,

%
'

'% *3 )(

The temperature at the throat reads #

The speed of sound is
0 %
#
And the mass flow rate reads # #

%( '3 )(
1

& 1

It is interesting to note that in this case the choking condition is obtained (
)

when the back pressure even reduced to less than 5% than original pressure (the
# #
pressure in the tank). While the pressure to achieve full supersonic flow through
#

the nozzle the pressure has to be below the 42% the original value. Thus, over
%( '3 )(
50% of the range of pressure a shock occores some where in the nozzle. In fact
in many industrial applications, these kind situations exist. In these applications a
small pressure difference can produce a shock wave and a chock flow.
1
For more practical example from industrial application point of view.
Example 6.2:
In the data from the above example (6.1) where would be shock’s location when
?
1 The meaning of the word practical is that reality the engineer does not given the opportunity or

determined the location of the shock but rather information such as pressures and temperature.

the back pressure is