Accession Number : ADA190856

Title :   The Structure of Sonic Underexpanded Turbulent Air Jets in Still Air.

Descriptive Note : Interim rept. 15 Jul 85-15 Aug 87,

Corporate Author : MICHIGAN UNIV ANN ARBOR DEPT OF AEROSPACE ENGINEERING

Personal Author(s) : Chuech, S G ; Lai, M C ; Faeth, G M

PDF Url : ADA190856

Report Date : Sep 1987

Pagination or Media Count : 118

Abstract : Turbulent subsonic, sonic and underexpanded round air jets, in still air, were studied both theoretically and experimentally. The following measurements were made: shock-wave structure of the underexpanded jets, using flash and continuous Schlieren photography; mean and fluctuating concentrations and mean static pressures, using laser-induced fluorescence; and mean and fluctuating streamwise velocities, using laser-Doppler anemometry. Analysis included: solution of the parabolized Navier-Stokes equations of motion; and use of effective adapted-jet exit conditions, to avoid the complexities of treating the shock-containing near field region of underexpanded jets. In both cases, turbulence properties were found using a k-epsilon turbulence model. Structure of the near-field region of the underexpanded jets was influenced by compressibility and turbulence levels at the jet exit. Mixing rates were reduced by compressibility when convective Mach numbers were greater than 0.5, in agreement with observations of Papamoschou and Roshko (1986); while increased turbulence levels at the jet exit increased mixing rates, which is a well-recognized effect for subsonic jets. The present parabolized Navier-Stokes method was successful for treating slug-flow exit conditions, but must be extended to treat effects of turbulent jet exit conditions. The effective adapted-jet approach was capable of treating various jet exit conditions; however, this approach provides no information concerning the shock-containing near-field region.

Descriptors :   *JET FLOW, *SUPERSONIC CHARACTERISTICS, COMPRESSIVE PROPERTIES, CONTINUITY, CONVECTION, DOPPLER SYSTEMS, LASER ANEMOMETERS, LASER INDUCED FLUORESCENCE, MACH NUMBER, MEAN, MIXING, NAVIER STOKES EQUATIONS, NEAR FIELD, PARABOLAS, RATES, REDUCTION, SCHLIEREN PHOTOGRAPHY, SHOCK WAVES, STATIC PRESSURE, TURBULENCE, VELOCITY, FLOW VISUALIZATION

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE