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Transition mechanisms in crossflow-dominated hypersonic flows with freestream acoustic noise

Transition mechanisms in crossflow-dominated hypersonic flows with freestream acoustic noise
Transition mechanisms in crossflow-dominated hypersonic flows with freestream acoustic noise
Transition to turbulence in high speed flows is determined by multiple parameters, many of which are not fully understood, leading to problems in developing physicsbased prediction methods. In this contribution, we compare transition mechanisms in configurations with unswept and swept leading-edges that are exposed to freestream acoustic disturbances. Direct numerical simulations are run at a Mach number of six with the same freestream noise, consisting of either fast or slow acoustic disturbances, with two different amplitudes to explore the linear and nonlinear aspects of receptivity and transition. For the unswept configuration, receptivity follows an established mechanism involving synchronisation of fast acoustic disturbances with boundary-layer modes. At high forcing amplitudes, transition proceeds via the formation of streaks and their eventual breakdown. In the swept case, the process of streak-induced transition is modified by the presence of a crossflow instability in the leading edge region. Linear stability analysis confirms the presence of a crossflow mode as well as weaker first and second mode waves. Both fast and slow types of forcing independently stimulate an unusual transition mechanism involving significantly narrower streaks than those arising from the crossflow instability behind the swept leading edge or those induced nonlinearly in the unswept case. In the observed transition process, the crossflow mode leads to a thin layer of streamwise vorticity that breaks up under the influence of high-spanwise wavenumber disturbances. These disturbances first appear in the leading-edge region.
3. Hypersonic flow, transition, aerodynamics
0022-1120
1-44
Cerminara, Adriano
6fd11181-c852-4558-82b5-5f7eac291a3f
Sandham, Neil
0024d8cd-c788-4811-a470-57934fbdcf97
Cerminara, Adriano
6fd11181-c852-4558-82b5-5f7eac291a3f
Sandham, Neil
0024d8cd-c788-4811-a470-57934fbdcf97

Cerminara, Adriano and Sandham, Neil (2020) Transition mechanisms in crossflow-dominated hypersonic flows with freestream acoustic noise. Journal of Fluid Mechanics, 1-44. (In Press)

Record type: Article

Abstract

Transition to turbulence in high speed flows is determined by multiple parameters, many of which are not fully understood, leading to problems in developing physicsbased prediction methods. In this contribution, we compare transition mechanisms in configurations with unswept and swept leading-edges that are exposed to freestream acoustic disturbances. Direct numerical simulations are run at a Mach number of six with the same freestream noise, consisting of either fast or slow acoustic disturbances, with two different amplitudes to explore the linear and nonlinear aspects of receptivity and transition. For the unswept configuration, receptivity follows an established mechanism involving synchronisation of fast acoustic disturbances with boundary-layer modes. At high forcing amplitudes, transition proceeds via the formation of streaks and their eventual breakdown. In the swept case, the process of streak-induced transition is modified by the presence of a crossflow instability in the leading edge region. Linear stability analysis confirms the presence of a crossflow mode as well as weaker first and second mode waves. Both fast and slow types of forcing independently stimulate an unusual transition mechanism involving significantly narrower streaks than those arising from the crossflow instability behind the swept leading edge or those induced nonlinearly in the unswept case. In the observed transition process, the crossflow mode leads to a thin layer of streamwise vorticity that breaks up under the influence of high-spanwise wavenumber disturbances. These disturbances first appear in the leading-edge region.

Text
Transition Mechanisms in Crossflow-Dominated Hypersonic Flows with Freestream Acoustic Noise - Accepted Manuscript
Restricted to Repository staff only until 21 October 2020.
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More information

Accepted/In Press date: 21 April 2020
Keywords: 3. Hypersonic flow, transition, aerodynamics

Identifiers

Local EPrints ID: 439682
URI: http://eprints.soton.ac.uk/id/eprint/439682
ISSN: 0022-1120
PURE UUID: db9a39f1-8387-4c34-9ea7-7fead93b6fee
ORCID for Neil Sandham: ORCID iD orcid.org/0000-0002-5107-0944

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Date deposited: 29 Apr 2020 16:31
Last modified: 29 Jul 2020 01:33

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