Study of Pressure Distributions on Simple Sharp-Nosed Models at Mach Numbers From 16 to 18 in Helium Flow Page: 3 of 43

                                
2                                                          NACA TN 4113
viscous solution. The first approach assumes that two separate regions
exist behind the shock: the viscous boundary layer and a zone of invis-
cid flow between the shock and the edge of the boundary layer. The sec-
ond approach assumes that only one region exists under the shock; this
region is treated by the boundary-layer equations. Reported studies
based on the first approach to the strong-interaction region are those
by Bertram (ref. 1), Kuo (ref. 2), Lees (refs. 5 and 4), and Lees and
Probstein (ref. 5). Investigations which use the second approach are
reported by Li and Nagamatsu (ref. 6) and Shen (ref. 7).
Results of experimental investigations on the viscous-compressible
effects in air have been reported by Bertram (ref. 8) for a Mach number
of 6.9 and by Kendall (ref. 9) for a Mach number of 5.8. Experimental
studies in helium flow have been reported by Hammitt and Bogdonoff
(refs. 10 and 11) for Mach numbers up to 14.5 and by Munson (ref. 12)
for a Mach number of 18.4.
The Mach number range for the present investigation was from 16 to
18, and the flow Reynolds number was from 0.9 X 106 to 1.5 x 106 per inch.
SYMBOLS
C              linear viscosity coefficient in relation  K/k; =C    TT
and determined from relation  C =  1+   - -1-M2    , for
2
Npr = 1
d              diameter
h              height of model
2              length of model
M              Mach number
p              pressure
Pb             back pressure
Ap             induced static pressure, measured surface pressure minus
inviscid pressure
Npr            Prandtl number