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Enhanced instability of supersonic boundary layer using passive acoustic feedback

Enhanced instability of supersonic boundary layer using passive acoustic feedback
Enhanced instability of supersonic boundary layer using passive acoustic feedback
Tripping of boundary-layers from laminar to turbulent flow, which may be needed in specific practical applications, requires introducing high amplitude disturbances into the boundary layers without large drag penalties. As a possible improvement on fixed trip devices, a technique based on feedback instability is demonstrated in the present contribution for a Mach 1.5 boundary layer. The compressible Navier-Stokes equations are solved directly using a high-order (fifth-order in space and third-order in time) finite difference method. The geometries tested include wall-mounted rectangular blocks and off-surface cylinders. For a particular combination of an upstream cylinder and downstream block, a feedback loop is observed to provide more robust self-amplification of disturbances than a cylinder alone, whereas blocks by themselves only enhance a convective instability. A Fourier analysis and an impulse response simulation are used to confirm the presence of an acoustic feedback loop for the cylinder-block configuration. A parametric study of the size of the cylinder, the height, and the location of the rectangular block is also provided. It is observed that the feedback strength is not monotonically related to the height and location of the rectangular block.
1070-6631
1-23
Tu, G
29b065a9-d61c-4105-9a53-ab93cfe33bd6
Hu, Zhiwei
dd985844-1e6b-44ba-9e1d-fa57c6c88d65
Sandham, Neil
0024d8cd-c788-4811-a470-57934fbdcf97
Tu, G
29b065a9-d61c-4105-9a53-ab93cfe33bd6
Hu, Zhiwei
dd985844-1e6b-44ba-9e1d-fa57c6c88d65
Sandham, Neil
0024d8cd-c788-4811-a470-57934fbdcf97

Tu, G, Hu, Zhiwei and Sandham, Neil (2016) Enhanced instability of supersonic boundary layer using passive acoustic feedback. Physics of Fluids, 28 (24103), 1-23. (doi:10.1063/1.4940324).

Record type: Article

Abstract

Tripping of boundary-layers from laminar to turbulent flow, which may be needed in specific practical applications, requires introducing high amplitude disturbances into the boundary layers without large drag penalties. As a possible improvement on fixed trip devices, a technique based on feedback instability is demonstrated in the present contribution for a Mach 1.5 boundary layer. The compressible Navier-Stokes equations are solved directly using a high-order (fifth-order in space and third-order in time) finite difference method. The geometries tested include wall-mounted rectangular blocks and off-surface cylinders. For a particular combination of an upstream cylinder and downstream block, a feedback loop is observed to provide more robust self-amplification of disturbances than a cylinder alone, whereas blocks by themselves only enhance a convective instability. A Fourier analysis and an impulse response simulation are used to confirm the presence of an acoustic feedback loop for the cylinder-block configuration. A parametric study of the size of the cylinder, the height, and the location of the rectangular block is also provided. It is observed that the feedback strength is not monotonically related to the height and location of the rectangular block.

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Accepted/In Press date: 4 January 2016
e-pub ahead of print date: 2 February 2016
Published date: February 2016
Organisations: Aeronautics, Astronautics & Comp. Eng

Identifiers

Local EPrints ID: 389598
URI: https://eprints.soton.ac.uk/id/eprint/389598
ISSN: 1070-6631
PURE UUID: 33443c60-4fa1-4967-9973-a613ca059c4b
ORCID for Neil Sandham: ORCID iD orcid.org/0000-0002-5107-0944

Catalogue record

Date deposited: 09 Mar 2016 14:57
Last modified: 07 Aug 2019 00:47

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Contributors

Author: G Tu
Author: Zhiwei Hu
Author: Neil Sandham ORCID iD

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