Journal of Fluid Mechanics

Papers

Origin of transonic buffet on aerofoils

J. D. CROUCHa1 c1, A. GARBARUKa2, D. MAGIDOVa2 and A. TRAVINa2

a1 The Boeing Company, Seattle, WA 98124-2207, USA

a2 Saint Petersburg Polytechnic University, St Petersburg, 195251 Russia

Abstract

Buffeting flow on transonic aerofoils serves as a model problem for the more complex three-dimensional flows responsible for aeroplane buffet. The origins of transonic aerofoil buffet are linked to a global instability, which leads to shock oscillations and dramatic lift fluctuations. The problem is analysed using the Reynolds-averaged Navier–Stokes equations, which for the foreseeable future are a necessary approximation to cover the high Reynolds numbers at which transonic buffet occurs. These equations have been shown to reproduce the key physics of transonic aerofoil flows. Results from global-stability analysis are shown to be in good agreement with experiments and numerical simulations. The stability boundary, as a function of the Mach number and angle of attack, consists of an upper and a lower branch – the lower branch shows features consistent with a supercritical bifurcation. The unstable modes provide insight into the basic character of buffeting flow at near-critical conditions and are consistent with fully nonlinear simulations. The results provide further evidence linking the transonic buffet onset to a global instability.

(Received August 14 2008)

(Revised February 20 2009)

Correspondence:

c1 Email address for correspondence: jeffrey.d.crouch@boeing.com

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