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Fast identification of transonic buffet envelope using computational fluid dynamics

Fast identification of transonic buffet envelope using computational fluid dynamics
Fast identification of transonic buffet envelope using computational fluid dynamics
Purpose – The paper presented a numerical method based on computational fluid dynamics that allows investigating the buffet envelope of reference equivalent wings at the equivalent cost of several two-dimensional, unsteady, turbulent flow analyses. The method bridges the gap between semi-empirical relations, generally dominant in the early phases of aircraft design, and three-dimensional turbulent flow analyses, characterised by high costs in analysis setups and prohibitive computing times.

Design/methodology/approach – Accuracy in the predictions and efficiency in the solution are two key aspects. Accuracy is maintained by solving a specialised form of the Reynolds–averaged Navier–Stokes equations valid for infinite-swept wing flows. Efficiency of the solution is reached by a novel implementation of the flow solver, as well as by combining solutions of different fidelity spatially.

Findings – Discovering the buffet envelope of a set of reference equivalent wings is accompanied with an estimate of the uncertainties in the numerical predictions. Just over 2,000 CPU hours are needed if it is admissible to deal with an uncertainty of ±1.0 deg in the angle of attack at which buffet onset/offset occurs. Halving the uncertainty requires significantly more computing resources, close to a factor 200 compared with the larger uncertainty case.

Practical implications – To permit the use of the proposed method as a practical design tool in the conceptual/preliminary aircraft design phases, the method offers the designer with the ability to gauge the sensitivity of buffet on primary design variables, such as wing sweep angle and chord to thickness ratio.

Originality/value – The infinite-swept wing, unsteady Reynolds–averaged Navier–Stokes equations have been successfully applied, for the first time, to identify buffeting conditions. This demonstrates the adequateness of the proposed method in the conceptual/preliminary aircraft design phases.
Buffet envelope, reference equivalent wings, computational fluid dynamics, infinite-swept wing, Uncertainty
309-316
Drofelnik, Jernej
e785f695-61ef-4afc-bf0a-9dc7966f5516
Da Ronch, Andrea
a2f36b97-b881-44e9-8a78-dd76fdf82f1a
Franciolini, Matteo
ff98a7b3-a108-44ef-96a1-3b4a3c7eed6d
Crivellini, Andrea
9a278077-53e7-4771-bfbc-85e374386ff5
Drofelnik, Jernej
e785f695-61ef-4afc-bf0a-9dc7966f5516
Da Ronch, Andrea
a2f36b97-b881-44e9-8a78-dd76fdf82f1a
Franciolini, Matteo
ff98a7b3-a108-44ef-96a1-3b4a3c7eed6d
Crivellini, Andrea
9a278077-53e7-4771-bfbc-85e374386ff5

Drofelnik, Jernej, Da Ronch, Andrea, Franciolini, Matteo and Crivellini, Andrea (2018) Fast identification of transonic buffet envelope using computational fluid dynamics. Aircraft Engineering and Aerospace Technology, 91 (2), 309-316. (doi:10.1108/AEAT-01-2018-0057).

Record type: Article

Abstract

Purpose – The paper presented a numerical method based on computational fluid dynamics that allows investigating the buffet envelope of reference equivalent wings at the equivalent cost of several two-dimensional, unsteady, turbulent flow analyses. The method bridges the gap between semi-empirical relations, generally dominant in the early phases of aircraft design, and three-dimensional turbulent flow analyses, characterised by high costs in analysis setups and prohibitive computing times.

Design/methodology/approach – Accuracy in the predictions and efficiency in the solution are two key aspects. Accuracy is maintained by solving a specialised form of the Reynolds–averaged Navier–Stokes equations valid for infinite-swept wing flows. Efficiency of the solution is reached by a novel implementation of the flow solver, as well as by combining solutions of different fidelity spatially.

Findings – Discovering the buffet envelope of a set of reference equivalent wings is accompanied with an estimate of the uncertainties in the numerical predictions. Just over 2,000 CPU hours are needed if it is admissible to deal with an uncertainty of ±1.0 deg in the angle of attack at which buffet onset/offset occurs. Halving the uncertainty requires significantly more computing resources, close to a factor 200 compared with the larger uncertainty case.

Practical implications – To permit the use of the proposed method as a practical design tool in the conceptual/preliminary aircraft design phases, the method offers the designer with the ability to gauge the sensitivity of buffet on primary design variables, such as wing sweep angle and chord to thickness ratio.

Originality/value – The infinite-swept wing, unsteady Reynolds–averaged Navier–Stokes equations have been successfully applied, for the first time, to identify buffeting conditions. This demonstrates the adequateness of the proposed method in the conceptual/preliminary aircraft design phases.

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More information

Accepted/In Press date: 19 March 2018
e-pub ahead of print date: 2 November 2018
Keywords: Buffet envelope, reference equivalent wings, computational fluid dynamics, infinite-swept wing, Uncertainty

Identifiers

Local EPrints ID: 423081
URI: http://eprints.soton.ac.uk/id/eprint/423081
PURE UUID: c1f16620-374a-4b45-a130-26889279ec4a

Catalogue record

Date deposited: 13 Aug 2018 16:31
Last modified: 19 Jul 2019 17:23

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Contributors

Author: Jernej Drofelnik
Author: Andrea Da Ronch
Author: Matteo Franciolini
Author: Andrea Crivellini

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