超音速気流変動特性に及ぼす湿度効果について

抄録

Humidity in working fluid affects on supersonic flow properties. The paper is to evaluate the flow quality of the indraft supersonic wind tunnel of Muroran Institute of Technology against moisture. The static pressure fluctuation is measured by means of an unsteady pressure sensor buried in the model of 10 degree aperture cone model installed in the test section. Results show that supersonic flow at Mach 2 is contaminated by self-sustained oscillation of condensation shock wave in case of relative humidity more than approximately 50%. It is also shown that static-pressure fluctuation to the dynamic pressure below a critical point with an absolute humidity 2[g/cm³] is attained below 0.1% in Mach 2 flow. Under atmospheric conditions between absolute humidity 2[g/cm³] and 6[g/cm³], static-pressure fluctuations may increase in the frequency range of 1--30[kHz] due to phase change of minute ice particles generated in the supersonic nozzle. Experimental observations on three-dimensional boundary-layer transition hypersensitive to free-stream humidity are exemplified.