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Low-frequency dynamics of shock-induced separation in a compression ramp interaction

Low-frequency dynamics of shock-induced separation in a compression ramp interaction
Low-frequency dynamics of shock-induced separation in a compression ramp interaction
The low-frequency dynamics of the shock-induced separation region in a Mach 2 compression ramp interaction is investigated by performing high-speed particle image velocimetry (HSPIV) measurements, at a rate of 6kHz, in a streamwise–spanwise plane. The HSPIV measurements made in the upstream turbulent boundary layer indicate the presence of spanwise strips of elongated regions of uniform streamwise velocity that extend to lengths greater than 30?, validating previous results based on planar laser scattering measurements obtained by Ganapathisubramani, Clemens & Dolling (J. Fluid Mech., vol. 585, 2007, p. 369). At a wall normal-location of y/?=0.2, a surrogate for separation based on a velocity threshold is found to fluctuate over a streamwise range of ±1.2?, consistent with previous studies. The amplitude of unsteadiness has contributions from at least two sources that are related to the incoming boundary layer. First, the velocity threshold based surrogate separation line exhibits large-scale undulations along the spanwise direction that conform to the passage of elongated low- and high-speed regions in the upstream boundary layer. This motion is classified as the local influence of the upstream boundary layer. Second, the spanwise-averaged surrogate separation is found to respond to the overall change in streamwise velocity in the incoming boundary layer and is classified as the global influence of the upstream boundary layer. However, this global influence includes the contributions from the elongated low- and high-speed regions. Preliminary findings based on statistical analysis suggest that the local influence contributes nearly 50% more than the global influence. Regardless, the low-frequency unsteadiness of the separation-region can be attributed to the local and global influences of the incoming boundary layer.
0022-1120
397-425
Ganapathisubramani, B.
5e69099f-2f39-4fdd-8a85-3ac906827052
Clemens, N.T.
9c4dd6c5-fdb8-4f5f-bf41-3b3643ed67ec
Dolling, D.S.
09e07695-f296-4a52-a99c-11f9153e9fe3
Ganapathisubramani, B.
5e69099f-2f39-4fdd-8a85-3ac906827052
Clemens, N.T.
9c4dd6c5-fdb8-4f5f-bf41-3b3643ed67ec
Dolling, D.S.
09e07695-f296-4a52-a99c-11f9153e9fe3

Ganapathisubramani, B., Clemens, N.T. and Dolling, D.S. (2009) Low-frequency dynamics of shock-induced separation in a compression ramp interaction. Journal of Fluid Mechanics, 636, 397-425. (doi:10.1017/S0022112009007952).

Record type: Article

Abstract

The low-frequency dynamics of the shock-induced separation region in a Mach 2 compression ramp interaction is investigated by performing high-speed particle image velocimetry (HSPIV) measurements, at a rate of 6kHz, in a streamwise–spanwise plane. The HSPIV measurements made in the upstream turbulent boundary layer indicate the presence of spanwise strips of elongated regions of uniform streamwise velocity that extend to lengths greater than 30?, validating previous results based on planar laser scattering measurements obtained by Ganapathisubramani, Clemens & Dolling (J. Fluid Mech., vol. 585, 2007, p. 369). At a wall normal-location of y/?=0.2, a surrogate for separation based on a velocity threshold is found to fluctuate over a streamwise range of ±1.2?, consistent with previous studies. The amplitude of unsteadiness has contributions from at least two sources that are related to the incoming boundary layer. First, the velocity threshold based surrogate separation line exhibits large-scale undulations along the spanwise direction that conform to the passage of elongated low- and high-speed regions in the upstream boundary layer. This motion is classified as the local influence of the upstream boundary layer. Second, the spanwise-averaged surrogate separation is found to respond to the overall change in streamwise velocity in the incoming boundary layer and is classified as the global influence of the upstream boundary layer. However, this global influence includes the contributions from the elongated low- and high-speed regions. Preliminary findings based on statistical analysis suggest that the local influence contributes nearly 50% more than the global influence. Regardless, the low-frequency unsteadiness of the separation-region can be attributed to the local and global influences of the incoming boundary layer.

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Published date: October 2009
Organisations: Aerodynamics & Flight Mechanics, Engineering Science Unit

Identifiers

Local EPrints ID: 182503
URI: http://eprints.soton.ac.uk/id/eprint/182503
ISSN: 0022-1120
PURE UUID: 243617d0-6328-434a-bb12-d9a8463619e2
ORCID for B. Ganapathisubramani: ORCID iD orcid.org/0000-0001-9817-0486

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Date deposited: 28 Apr 2011 09:12
Last modified: 15 Mar 2024 03:37

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Contributors

Author: N.T. Clemens
Author: D.S. Dolling

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