On the basis of the similarity rule for jet interaction, a hot jet can be simulated in a cryogenic wind tunnel with a test gas at ambient or moderately elevated temperatures. By using this approach, jet-temperature effects on the base pressure of a cylindrical afterbody model at transonic speeds have been investigated in the 0.1-m transonic cryogenic wind tunnel at the National Aerospace Laboratory. Mixtures of nitrogen and either methane, argon, or helium at varying temperatures were used as a jet gas to determine separate effects of jet temperature, specific heat ratio, and gas constant. It has been found that data obtained for various jet conditions can be correlated very well with two similarity parameters: the plume maximum diameter for the plume shape effect and the jet to freestream mass flux ratio for the jet entrainment effect. To verify this similarity rule, the same model was tested in an ambient wind tunnel. It was found that an ambient temperature gas having low molecular weight could simulate the jet temperature effects on the transonic base pressure.
ASJC Scopus subject areas
- Aerospace Engineering