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  • Air condensation in rapidly expanding hypersonic flow

    Paper ID



    • F.L. Daum
    • G. Gyarmathy


    United States Air Force, Aerospace Research Laboratories, Wright-Patterson Air Force Base, Fluid Dynamics Facilities Laboratory






    Tire results of a previous experimental study of air condensation in a hypersonic wind tunnel have been extended to conditions of lower static pressures and slightly greater Mach numbers. It was found that the high level of attainable supercooling at the lower pressu res does not follow a simple extrapolation of the higher pressure results, as was expect ed. A comparison of the present data with the limited corresponding experimental data on pure nitrogen or oxygen vapor, which are available in the literature, led to a new interpretation of the observed behavior of air condensation in low density hypersonic flows. A theoretical analysis, which indicated a strong influence of expansion rate on the onset of spontaneous condensation, was found to be substantiated by the experimental data. Further, the theoretical study led to the determination of a parameter which correlates the onset points obtained in different tunnels, with the exception of a few points obtained with air. Explanations of these exceptions and of the whole of observed con- densati on characteristics are offered. A chart, modified according to the present experimental findings, is presented for use in determining the stagnaticn temperature at which air condensation will occur in the test section of hj’personic wind tunnels in the Mach number range from 8 to 24.