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Compressible spreading rates of supersonic coaxial jets

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Abstract

The compressible spreading rates of two supersonic coaxial jets were studied experimentally. The center jet had a fully-expanded Mach number of 3, and the outer jet of M = 1.8. The geometries of the center jet were circular and rectangular with two configurations, both with a 3∶1 aspect-ratio. The convective Mach numbers were varied in the range between 0.25 < M c< 2.25. This was accomplished by varying the density ratio between the center jet and the coaxial jet, as well as the velocity ratio. The experimental compressible spreading rate was determined using Schlieren photography and total-pressure measurements. The spreading rate of the center circular jet decreased with increasing convective Mach number until it reached a constant value of 0.2 to 0.3 of the incompressible spreading rate for M c>1.4. The rectangular jets exhibited a similar drop, at the same range of M c, but their spreading rate was higher relative to the circular jet in the entire convective Mach number range.

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Abbreviations

AR :

aspect ratio

b :

shear layer thickness

D :

exit diameter

M :

Mach number

p :

pressure

r :

radial coordinate

R :

velocity ratio, R = u 2/u 1

S :

density ratio, S = r 2/r 1

S.R. :

spreading rate

T :

temperature

u :

velocity

X :

axial coordinate

ϱ :

density

γ :

ratio of specific heats

δ w :

“vorticity” thickness

0:

stagnation

1:

primary, center jet

2:

secondary, coaxial jet

C :

convective

CL :

centerline

comp. :

compressible

D :

design conditions

d :

downstream of shock

e :

equivalent

incomp :

incrompressible

M :

minimum

t :

throat (or total for pressure)

u :

upstream of shock

References

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Authors and Affiliations

  1. Research Dept., Naval Weapons Center, 93555-6001, China Lake, CA, USA

    K. C. Schadow, E. Gutmark & K. J. Wilson

Authors
  1. K. C. Schadow
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  2. E. Gutmark
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  3. K. J. Wilson
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Schadow, K.C., Gutmark, E. & Wilson, K.J. Compressible spreading rates of supersonic coaxial jets. Experiments in Fluids 10, 161–167 (1990). https://doi.org/10.1007/BF00215025

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  • DOI: https://doi.org/10.1007/BF00215025

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