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Visualization of Supersonic Free and Confined Jet using Planar Laser Mie Scattering Technique

Karthick, SK and Jagadeesh, G and Reddy, KPJ (2016) Visualization of Supersonic Free and Confined Jet using Planar Laser Mie Scattering Technique. In: JOURNAL OF THE INDIAN INSTITUTE OF SCIENCE, 96 (1). pp. 29-45.

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Planar Laser Mie Scattering (PLMS) imaging technique is employed in supersonic axisymmetric free jet and supersonic rectangular confined jet to extract out the prominent flow features. Efficient seeding of the flow field is achieved using an in-house seeder unit which employs modified Laskin Nozzle. For this imaging, flow field is seeded with particles of water or DEHS in case of free jet studies and with acetone for confined jet studies. Using high power laser and high speed camera, flow field is illuminated and captured. A series of simple image processing routines are carried out to extract the noticeable attributes of the flow. Prominent flow features like Mach disc, shear layer instability and shock cells are captured in the instantaneous PLMS images of a severely under-expanded supersonic axisymmetric free jet of design Mach number (M-D) 1.367. Qualitative increase in the shock cell spacing (L-s) for increasing Mach number ratio (M-R) is observed for time-averaged PLMS imaging of a supersonic axisymmetric free jet (M-D = 2.0 & 2.5). Also an effective increase in the jet width of an over-expanded jet undergoing screech is noticed. Major flow features like large scale coherent structures and terminal potential core instability are seen clearly in the instantaneous PLMS images of a rectangular supersonic confined jet of M-PD = 2.0. Shock cell spacing and mixing layer formation are observed distinctly in the time-averaged PLMS images. Qualitative increase in L-s for increasing stagnation pressure ratio (SPR) is highlighted along with the increase in the wavelength of the potential core instability. More details regarding the experimentation procedure and the underlying physics behind the observed flow features along with the variations encountered for different operating conditions are discussed elaborately in this paper.

Item Type: Journal Article
Additional Information: Copy right for this article belongs to the INDIAN INST SCIENCE, INDIAN INST SCIENCE, BANGALORE 560012, INDIA
Keywords: PLMS; Supersonic Free Jet; Supersonic Confined Jet; Visualization Techniques
Department/Centre: Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering)
Date Deposited: 16 Jun 2016 05:36
Last Modified: 16 Jun 2016 05:36
URI: http://eprints.iisc.ac.in/id/eprint/54020

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