Flow active control activities at Onera
C.DESPRE - J.L. GOBERTONERA
Thursday, May 4th, 11.00 a.m. CERFACS Conference Room
Abstract :
In 1997, the O.N.E.R.A (French National Aerospace Research Establishment) sat up a multidisciplinary project on the subject of Active Flow Control. Experimental work, computational fluid dynamic studies, modelling and synthesis of control laws constitute the main activities of this project.
The investigations include:
1. control of convective instabilities,
2. control of aerodynamic instabilities leading to buffeting phenomenon in transonic conditions,
3. control of the 3D separation at a wing-fuselage junction,
4. 3D separation control on an ellipsoid cylinder model
5. side force control on a generic forebody at high angle of attack
6. control of vortex breakdown on a Delta wing.
The presentation will be performed in two phases :
1. A short description of the project organisation and the different activities will be given.
2. More technical details will be given on the part dedicated to buffet active control.
In some transonic flow conditions, the shock wave/turbulent boundary layer interaction and flow separation on an aircraft wing, induce aerodynamic flow instabilities called aerodynamic buffet. By coupling with the proper modes of the wing structure, the aerodynamic buffet instabilities generate the buffeting phenomenon. This type of instabilities have an important influence on the behaviour of the aircraft. The buffet phenomenon appears at high lift coefficient when the Mach number or the angle of attack of the aircraft increases. The buffet loads due to flow separation on the wing may cause serious fatigue problems and have an important impact on the structural integrity of the aircraft. The flight envelope is limited by the phenomenon. The objective of this study is to cancel or at least to drastically reduce the aerodynamic buffet instabilities due to this type of flow by an active control system. For that purpose, a new moving part of the wing actuator, has been designed at ONERA. It can be moved to different static positions or be driven with dynamic movements.
In order to get a better understanding on the way the actuator modifies flow separation and shock oscillation over the airfoil, experimental and numerical approaches have been used. Results on these approaches will be presented.
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