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Wide domain simulations of flow over an unswept laminar wing section undergoing transonic buffet

Wide domain simulations of flow over an unswept laminar wing section undergoing transonic buffet
Wide domain simulations of flow over an unswept laminar wing section undergoing transonic buffet
Transonic buffet is an unsteady flow phenomenon that limits the safe flight envelope of modern aircraft. Scale-resolving simulations with span-periodic boundary conditions can provide detailed insight into the flow physics associated with buffet and can help to calibrate simplified models that are needed, for example, to develop more efficient wings based on laminar-flow supercritical sections.
However, such simulations are often feasible only for severely restricted spanwise domains. In the current contribution, we analyse an unswept laminar-flow wing section (of Dassault Aviation’s
V2C profile) at a moderate Reynolds number of Re = 500,000 and a Mach number of M = 0.7 with spanwise domains equal to 5% and 100% of the airfoil chord. An implicit large-eddy simulation methodology, using a spectral error estimator to control the action of a high-order filter, is first validated against direct numerical simulations and then used for the domain width study.
Quantitative differences, due to domain size, include an increase in amplitude and regularity of the buffet oscillations in the wider domain. Nevertheless, space-time analysis shows that key physical phenomena such as upstream-propagating shock waves are properly represented in the narrow domain and there is limited sensitivity to domain size of the aerodynamic coefficients. Even in the very wide domain, which is an order of magnitude wider than the largest turbulent structures measured at the trailing edge, certain features remain two-dimensional, including the shock and expansion waves that interact with the boundary layer upstream of transition. The transition mechanism is found to have subtle variations during a typical buffet cycle, with Kelvin-Helmholtz
structures prominent during low-lift phases and oblique modes developing behind shock/boundarylayer interactions during high-lift phases. The availability of the wide-domain data is used for further study of the buffet mechanism, considering phase-averaged data and instantaneous flow fields to show the global structure of the buffet oscillation.
CFD, Transonic flow, large eddy simulation, moderate Reynolds numbers
2469-990X
Zauner, Markus
c0207f79-62cc-4909-8aa0-6bb9d99e1ea3
Sandham, Neil
0024d8cd-c788-4811-a470-57934fbdcf97
Zauner, Markus
c0207f79-62cc-4909-8aa0-6bb9d99e1ea3
Sandham, Neil
0024d8cd-c788-4811-a470-57934fbdcf97

Zauner, Markus and Sandham, Neil (2020) Wide domain simulations of flow over an unswept laminar wing section undergoing transonic buffet. Physical Review Fluids. (In Press)

Record type: Article

Abstract

Transonic buffet is an unsteady flow phenomenon that limits the safe flight envelope of modern aircraft. Scale-resolving simulations with span-periodic boundary conditions can provide detailed insight into the flow physics associated with buffet and can help to calibrate simplified models that are needed, for example, to develop more efficient wings based on laminar-flow supercritical sections.
However, such simulations are often feasible only for severely restricted spanwise domains. In the current contribution, we analyse an unswept laminar-flow wing section (of Dassault Aviation’s
V2C profile) at a moderate Reynolds number of Re = 500,000 and a Mach number of M = 0.7 with spanwise domains equal to 5% and 100% of the airfoil chord. An implicit large-eddy simulation methodology, using a spectral error estimator to control the action of a high-order filter, is first validated against direct numerical simulations and then used for the domain width study.
Quantitative differences, due to domain size, include an increase in amplitude and regularity of the buffet oscillations in the wider domain. Nevertheless, space-time analysis shows that key physical phenomena such as upstream-propagating shock waves are properly represented in the narrow domain and there is limited sensitivity to domain size of the aerodynamic coefficients. Even in the very wide domain, which is an order of magnitude wider than the largest turbulent structures measured at the trailing edge, certain features remain two-dimensional, including the shock and expansion waves that interact with the boundary layer upstream of transition. The transition mechanism is found to have subtle variations during a typical buffet cycle, with Kelvin-Helmholtz
structures prominent during low-lift phases and oblique modes developing behind shock/boundarylayer interactions during high-lift phases. The availability of the wide-domain data is used for further study of the buffet mechanism, considering phase-averaged data and instantaneous flow fields to show the global structure of the buffet oscillation.

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More information

Accepted/In Press date: 24 July 2020
Keywords: CFD, Transonic flow, large eddy simulation, moderate Reynolds numbers

Identifiers

Local EPrints ID: 443120
URI: http://eprints.soton.ac.uk/id/eprint/443120
ISSN: 2469-990X
PURE UUID: c6cc28e4-84b1-42c6-af31-cc0f7aea0655
ORCID for Markus Zauner: ORCID iD orcid.org/0000-0002-6644-2990
ORCID for Neil Sandham: ORCID iD orcid.org/0000-0002-5107-0944

Catalogue record

Date deposited: 11 Aug 2020 16:34
Last modified: 18 Feb 2021 16:52

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