Loading...

Investigation of the effect of turbulence intensity and nozzle exit boundary layer thickness on stability pattern of subsonic jet

Gohardehi, S ; Sharif University of Technology | 2019

592 Viewed
  1. Type of Document: Article
  2. DOI: 10.1051/meca/2018041
  3. Publisher: EDP Sciences , 2019
  4. Abstract:
  5. In this study, factors affecting the noise generation by instability waves in a subsonic jet with acoustic Mach number of 0.5 are investigated using linear stability analysis. The base flow required for instability analysis is obtained by modeling the jet stream based on the k-ϵ turbulence model and using the empirical coefficients suggested by Thies and Tam [1]. The resulting base flow profiles are used to solve the linear instability equation, which governs the pressure perturbation for obtaining the eigenvalues and eigenfunctions. The results of linear instability analysis for phase and amplitude of pressure fluctuations are compared against the existing experimental data, which demonstrated the validity of the conducted instability analysis. The effects of turbulence intensity and thickness of the boundary layer at the jet nozzle exit on the results of the linear instability analysis are investigated. The results show that as the turbulence intensity at nozzle exit increases, the frequency range for which the spatial growth rates are positive grows smaller, and except for very low frequencies, this leads to decreased growth rates in both axisymmetric and first azimuthal modes. Also, in both of these modes, an increase in the thickness of the boundary layer at nozzle exit leads to a decrease in perturbation's growth rates in the surveyed frequency ranges. © AFM, EDP Sciences 2019
  6. Keywords:
  7. Boundary layer thickness ; Turbulence intensity ; Turbulence jet noise ; Aerodynamics ; Boundary layer flow ; Boundary layers ; Eigenvalues and eigenfunctions ; Jets ; Linear stability analysis ; Nozzles ; Turbulence models ; Empirical coefficients ; Instability analysis ; Jet noise ; Linear instability analysis ; Linear Stability ; Pressure perturbation ; Atmospheric thermodynamics
  8. Source: Mechanics and Industry ; Volume 20, Issue 1 , 2019 ; 22577777 (ISSN)
  9. URL: https://www.mechanics-industry.org/articles/meca/abs/2019/01/mi170277/mi170277.html