Rao, SMV and Karthick, SK and Anand, A (2020) Elliptic supersonic jet morphology manipulation using sharp-tipped lobes. In: Physics of Fluids, 32 (8).
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Abstract
Elliptic nozzle geometry is attractive for mixing enhancement of supersonic jets. However, jet dynamics, such as flapping, gives rise to high-intensity tonal sound. We experimentally manipulate the supersonic elliptic jet morphology by using two sharp-tipped lobes. The lobes are placed on either end of the minor axis in an elliptic nozzle. The design Mach number and the aspect ratio of the elliptic nozzle and the lobed nozzle are 2.0 and 1.65. The supersonic jet is exhausted into ambient under almost perfectly expanded conditions. Time-resolved schlieren imaging, longitudinal and cross-sectional planar laser Mie scattering imaging, planar Particle Image Velocimetry (PIV), and near-field microphone measurements are performed to assess the fluidic behavior of the two nozzles. Dynamic Mode Decomposition (DMD) and proper orthogonal decomposition analyses are carried out on the schlieren and the Mie scattering images. Mixing characteristics are extracted from the Mie scattering images through the image processing routines. The flapping elliptic jet consists of two dominant DMD modes, while the lobed nozzle has only one dominant mode, and the flapping is suppressed. Microphone measurements show the associated noise reduction. The jet column bifurcates in the lobed nozzle enabling a larger surface contact area with the ambient fluid and higher mixing rates in the near-field of the nozzle exit. The jet width growth rate of the two-lobed nozzle is about twice that of the elliptic jet in the near-field, and there is a 40 reduction in the potential core length. PIV contours substantiate the results. © 2020 Author(s).
| Item Type: | Journal Article |
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| Publication: | Physics of Fluids |
| Publisher: | American Institute of Physics Inc. |
| Additional Information: | The copyright of this article belongs to American Institute of Physics Inc. |
| Keywords: | Aspect ratio; Brillouin scattering; Growth rate; Image processing; Microphones; Mixing; Morphology; Noise abatement; Nozzle design; Nozzles; Velocity measurement, Dynamic mode decompositions; Mie scattering image; Mixing characteristics; Mixing enhancement; Nozzle geometries; Particle image velocimetries; Planar laser mie scatterings; Proper orthogonal decompositions, Supersonic aerodynamics |
| Department/Centre: | Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering) |
| Date Deposited: | 15 Jan 2021 06:24 |
| Last Modified: | 15 Jan 2021 06:24 |
| URI: | http://eprints.iisc.ac.in/id/eprint/67401 |
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