Page 77 - 48Fundamentals of Compressible Fluid Mechanics

In this Chapter a discussion on steady state flow though a smooth and continuous
area flow rate (steady state) is presented. A discussion about the flow through
a converging–diverging nozzle is also part of this Chapter. The isentropic flow
models are important because two main reasons: one, it provides the information
about the trends and important parameters, two, the correction factors later can be
introduced to account for deviations from the ideal state.

4.1 Stagnation State for Ideal Gas Model

4.1.1 General Relationship

It is assumed that the flow is one–
dimensional. Figure (4.1) describes
a gas flows through a diverging–
converging nozzle. It has been found
that a theoretical state known as the
stagnation state is very useful in simpli-
fying the solution and treatment of the P B = P 0
flow. The stagnation state is a theoret- P
Subsonic
ical state in which the flow is brought P 0
M < 1
into a complete motionless condition in
isentropic process without other forces Supersonic
(e.g. gravity force). Several properties M > 1
that can be represented by this theoret-
distance, x
ical process which include temperature,
pressure, and density et cetera and de- Fig. 4.1: Flow of a compressible substance
(gas) thorough a converging diverg-
ing nozzle
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