NOISE FROM SUPERSONIC COAXIAL JETS, PART 1: MEAN FLOW PREDICTIONS

• Published in: Journal of sound and vibration Vol. 200; no. 5; pp. 643 - 663
• Main Authors: Dahl, M.D., Morris, P.J.
• Format: Journal Article
• Language: English
• Published: London Elsevier Ltd 13.03.1997; Elsevier
• Subjects: Acoustics; Aeroacoustics and atmospheric sound; Aeroacoustics, atmospheric sound; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Physics; Airborne sound; Supersonic flow; Supersonic jet; Numerical methods; Acoustics; Coaxial jet; Mixing layer; Parabolic equation; Acoustic radiation; Shear layer; Boundary layers; Analytical function; Jet propulsion
• ISSN: 0022-460X; 1095-8568
• DOI: 10.1006/jsvi.1996.0723

Recent theories for supersonic jet noise have used an instability wave noise generation model to predict radiated noise. This model requires a known mean flow that has typically been described by simple analytic functions for single jet mean flows. The mean flow of supersonic coaxial jets is not described easily in terms of analytic functions. To provide these profiles at all axial locations, a numerical scheme is developed to calculate the mean flow properties of a coaxial jet. The Reynolds-averaged, compressible, parabolic boundary layer equations are solved using a mixing length turbulence model. Empirical correlations are developed to account for the effects of velocity and temperature ratios and Mach number on the shear layer spreading. Both normal velocity profile and inverted velocity profile coaxial jets are considered. The mixing length model is modified in each case to obtain reasonable results when the two stream jet merges into a single fully developed jet. The mean flow calculations show both good qualitative and quantitative agreement with measurements in single and coaxial jet flows.