The Mixing of Unbounded Coaxial Compressible Streams

An invest igat ion was made of the over-all characteristics associated wi th unbounded mixing of axially symmetr ic compressible coaxial air streams. Experiments were performed to determine the effects of what are considered the fundamenta l parameters of the problem (the init ial Mach numbers and init ial s tagnat ion temperature ratio of the streams) . Included in the range of experiments were primary Mach numbers of 2.60, 0.97 and 0.68, secondary Mach numbers of 0.45, 0.25 and 0.00, and stagnat ion temperature ratios of 1.00 and 1.429. Mass flows in the mixing region, and hence mixing rates were computed from the experimenta l data for the range of parameters tested. The experimental (and to a lesser extent the analytical) results exhibited a very marked effect of the secondary Mach number . This effect was greatest for the subsonic primary Mach numbers . The over-all spreading was less for Mi = 2.60 and the effect of the secondary Mach n u m ber was less pronounced. The effect of increased temperature ratio was to increase the over-all spreading. A practical correlation between the spreading rates was found for the subsonic Mach numbers . For a constant primary Mach n u m b e r the spreading angle of the mixing region seems to depend linearly on the secondary Mach number .