Visualisation of underexpanded jet flowfields in the presence of an intrusive tab
- 246 Downloads
This paper investigates the influence of a single intrusive tab has on the flowfield of a supersonic jet. When a tab is added to the jet, an increase in the fundamental screech frequency is observed in acoustic spectra. High resolution schlieren imaging reveals alteration of both the shock structure and preferred instability mode in the jet. Two-point spatial correlation of schlieren images shows the transition from a lateral flapping mode to a punctuated toroid screech mode. This change in dominant instability mode produces a change in coherent structure wavelength that correlates well to the observed screech frequency shift in the acoustic data. The high quality of the schlieren images also allows the counter-rotating vortex pair produced by an individual tab to be identified. Images of the radial density gradient are used to estimate vortex pair location, and a statistical estimate for the trajectory of the vortex pair is produced. The vortex pair path identification technique shows that the path of the vortex pair is constrained close to the exit of the nozzle and increasingly variant in space with greater downstream distance. The vortex trajectory is shown to alter the sonic line and thus the spatial extent of the embedded shock structures.
KeywordsAeroacoustics Schlieren Free Jet Supersonic
The authors would like to acknowledge the funding of the Australian Research Council in supporting this research.
- Davies MG, Oldfield DES (1962) Tones from a choked axisymmetric jet. ii. the self-excited loop and mode of oscillation. Acustica 12(4):267–277Google Scholar
- Hileman J, Samimy M (2003) Effects of vortex generating tabs on noise sources in an ideally expanded mach 1.3 jet. Int J Aeroacoust 2(1):35–63Google Scholar
- Mason-Smith N, Edgington-Mitchell D, Buchmann NA, Honnery DR, Soria J (2015) Shock structures and instabilities formed in an underexpanded jet impinging on to cylindrical sections. Shock Waves 1–12Google Scholar
- Shen H, CKW Tam (2002) Three-dimensional numerical simulation of the jet screech phenomenon. AIAA J 40(1):33–41Google Scholar
- Suzuki T, Lele SK (2003) Shock leakage through an unsteady vortex-laden mixing layer: application to jet screech. J Fluid Mech 490:139–167Google Scholar
- Westley R, Lilley GM (1952) An investigation of the noise field from a small jet and methods for its reduction. In: Report No. 53, College of Aeronautics, Cranfield, EnglandGoogle Scholar
- Westley R, Woolley JH (1975) The near field sound pressures of a choked jet when oscillating in the spinning mode. In: AIAA 8th Aeroacoustics Conference, Paper AIAA-83-0706Google Scholar