Sugarno, MI and Sriram, R and Karthick, SK and Jagadeesh, G (2022) Unsteady pulsating flowfield over spiked axisymmetric forebody at hypersonic flows. In: Physics of Fluids, 34 (1).
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Abstract
The paper gives experimental observations of the hypersonic flow past an axisymmetric flat-face cylinder with a protruding sharp-tip spike. Unsteady pressure measurements and high-speed schlieren images are performed in tandem on a hypersonic Ludwieg tunnel at a freestream Mach number of M � = 8.16 at two different freestream Reynolds numbers based on the base body diameter (R e D = 0.76 � 10 6 and 3.05 � 10 6). The obtained high-speed images are subjected further to modal analysis to understand the flow dynamics parallel to the unsteady pressure measurements. The protruding spike of length to base body diameter ratio of l / D = 1 creates a familiar form of an unsteady flowfield called "pulsation."Pressure loading and fluctuation intensity at two different ReD cases are calculated. A maximum drop of 98.24% in the pressure loading and fluctuation intensity is observed between the high and low ReD cases. Due to the low-density field at low ReD case, almost all image analyses are done with the high ReD case. Based on the analysis, a difference in the pulsation characteristics is noticed, which arises from two vortical zones, each from a system of two "λ"shocks formed during the "collapse"phase ahead of the base body. The interaction of shedding vortices from the λ-shocks' triple-points, along with the rotating stationary waves, contributes to the asymmetric high-pressure loading and the observation of shock pulsation on the flat-face cylinder. The vortical interactions forming the second dominant spatial mode with a temporal mode carry a dimensionless frequency (f 2 D / u � � 0.34) almost twice that of the fundamental frequency (f 1 D / u � � 0.17). The observed frequencies are invariant irrespective of the ReD cases. However, for the high-frequency range, the spectral pressure decay is observed to follow an inverse and -7/3 law for the low and high ReD cases, respectively. © 2022 Author(s).
| Item Type: | Journal Article |
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| Publication: | Physics of Fluids |
| Publisher: | American Institute of Physics Inc. |
| Additional Information: | The copyright for this article belongs to American Institute of Physics Inc. |
| Keywords: | Cylinders (shapes); Flow fields; Hypersonic flow; Image analysis; Modal analysis; Parallel flow, Axisymmetric; Fluctuations intensity; Freestream mach number; High Speed; Measurement speed; Pressure fluctuation; Pressure loading; Schlieren image; Sharp tip; Unsteady pressure measurements, Reynolds number |
| Department/Centre: | Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering) |
| Date Deposited: | 08 Feb 2022 10:22 |
| Last Modified: | 08 Feb 2022 10:22 |
| URI: | http://eprints.iisc.ac.in/id/eprint/71165 |
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