Control of Separated Flows and Buffeting in Transonic Flow
Abstract
In transonic flow conditions, the shock wave / turbulent boundary layer interaction and flow separations on the wing upper surface of a civil aircraft, which induce flow instabilities (buffet) and then structure vibrations, buffeting can greatly influence the aerodynamic behavior. The buffet phenomenon appears when the Mach number or the angle of attack of the aircraft increases. This phenomenon limits the aircraft's flight envelope. The objective of this study is to cancel or to decrease the aerodynamic instabilities (unsteady separation, shock location movement) due to this type of flow by control systems. The following actuators can be used: Vortex Generators situated upstream of the shock location and a new moving part designed by ONERA and situated at the trailing edge of the wing, Trailing Edge Deflector or TED. It looks like an adjustable Divergent Trailing Edge. It is an active actuator, it can take different deflections or be driven by dynamic motions up to 250 Hz. Tests were performed in transonic 2D and 3D flow with models well equipped with unsteady pressure transducers. For high lift coefficients, a selected deflection of the Trailing Edge Deflector increases the wing aerodynamic performances and delays the buffet onset. Furthermore, in 2D flow buffet condition, the Trailing Edge Deflector, driven by a closed loop active control using the measurements of the unsteady wall static pressures, can greatly reduce the buffet. In 3D flow buffeting conditions, the 2D flow control principle is available but some differences must be considered. Vortex generators have a great impact on the separated flows. The separated flow instabilities are greatly reduced and the buffet is totally controlled even for strong instabilities. The aerodynamic performances of the airfoil are also greatly increased.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 2004
- Accession Number
- ADA442052
Entities
People
- A. Le Pourhiet
- A. Mignosi
- D. Caruana
- M. Correge
Organizations
- Office National d'Études et de Recherches Aérospatiales