<DOC>
<DOCNO>
656
</DOCNO>
<TITLE>
departure from dissociation equilibrium in a hypersonic nozzle .
</TITLE>
<AUTHOR>
bray, k.n.c.
</AUTHOR>
<BIBLIO>
a.r.c. 19, 983, march 1958 .
</BIBLIO>
<TEXT>
the equations of motion for the flow of an ideal dissociating gas
through a nearly conical nozzle have been solved numerically, assuming
a simple equation for the rate of dissociation, and a number of
different values of the rate constant . the results of these
calculations suggest that deviations from dissociation equilibrium will
occur in the nozzle if the rate constant lies within a very wide range
of values . they also suggest that once such a deviation has begun the
gas will very rapidly/freeze/, so that the dissociation fraction will
remain almost constant if the flow is expanded further, or even if it
passes through a constant area test section . an approximate method
of solution, making use of this property of sudden/freezing/of the flow,
 has been developed and applied to the problem of estimating the
deviations from equilibrium under a wide range of conditions . if all
the assumptions made in this report are accepted, then lack of
dissociation equilibrium may be expected in the working sections of
hypersonic wind tunnels and hypersonic shock tubes .
it is shown, however, that the flow behind a normal shock wave in such a
 wind tunnel will not be greatly affected by any freezing that may take
place in the nozzle upstream of the shock wave . even so, the stand-off
distance of a shock wave in front of a blunt model may be quite
sensitive to deviations from equilibrium .
</TEXT>
</DOC>
