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Transitional separation bubbles and unsteady aspects of aerofoil stall

Published online by Cambridge University Press:  03 February 2016

N. D. Sandham
N. D. Sandham*
Affiliation:
Aerodynamics and Flight Mechanics Research Group, School of Engineering Sciences, University of Southampton, Southampton, UK
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Abstract

A time-accurate solution method for the coupled potential flow and integral boundary-layer equations is used to study aerofoils near stall, where laboratory experiments have shown high-amplitude low-frequency oscillations. The laminar-turbulent transition model incorporates an absolute instability formulation, which allows the transition process in separation bubbles to be sustained in the absence of upstream disturbances, in agreement with recent direct numerical simulations. The method is demonstrated to capture large scale flow oscillations with Strouhal numbers and amplitudes comparable to experiments. The success of this particular physical model suggests that bubble bursting is primarily due to a potential-flow/boundary-layer interaction effect, in which relatively simple models of boundary layer transition and turbulence suffice to describe the key phenomena.

Type
Research Article
Information
The Aeronautical Journal , Volume 112 , Issue 1133 , July 2008 , pp. 395 - 404
Copyright
Copyright © Royal Aeronautical Society 2008 

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