The aim of this work programme was to develop a capability to understand and predict transonic buffet on wings fitted with buffet control devices. Wind tunnel tests were performed on a half model with buffet control devices fitted to measure dynamic flow characteristics during buffet onset.
Unsteady RANS and DES CFD calculations were carried out, validated against the wind tunnel data. The CFD calculations were then used to develop an improved understanding of transonic wing buffet. An industrialised computational method was developed to enable buffet prediction to be carried out whilst designing wings with buffet control devices fitted.
Buffet is a flow instability which can cause structural vibration (“buffeting”) on civil and military aircraft. Transonic wing buffet is important to civil aircraft designers, because it defines a limit to cruise flight conditions which impacts on airframe cost and efficiency. As a result, there is an increasing interest in predicting buffet offset early in the design process, and in delaying or alleviating the effects of buffet by active or passive means. The practical difficulties of modelling buffet have been known for many years and much research has been undertaken with ever more sophisticated modelling tools to analyse the phenomenon, with a focus on two-dimensional aerofoil flows. More recently attempts have been made to reduce the effect of buffet, but these have been hampered by a lack of understanding of the physics of transonic buffet on three-dimensional swept wings.
The aims of the BUCOLIC programme were to significantly improve our understanding of the underlying flow physics and to develop techniques to predict buffet in a practical timescale for industrial aircraft design. These aims were addressed using a combination of experimental investigations of buffet on a representative transport aircraft wing in the Aircraft Research Association’s industrial transonic wind tunnel, and numerical simulations at the University of Liverpool.