The Structure of Sonic Underexpanded Turbulent Air Jets in Still Air.
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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1987
- Accession Number
- ADA190856
Entities
People
- Gerard M. Faeth
- M. C. Lai
- S. G. Chuech
Organizations
- University of Michigan