Transonic Buffet Control on 3D Turbulent Wings using Fluidic Devices. Part 2: an experimental investigation of a closed loop methodology.

Abstract : The presented paper aims at giving an overview of the work performed in the ONERA's internal research project BUFET'N Co addressing the experimental characterization and the control of the buffet phenomenon on 3D turbulent wings in transonic flow conditions. This paper summarizes the main investigations leading to the definition of a closed loop methodology of buffet control and its experimental demonstration. Several wind tunnel tests campaigns enabled to characterize the buffet aerodynamic instability and to study the efficiency of fluidic control devices designed and manufactured by ONERA. The analyses of the open loop databases (wall pressure fluctuations) demonstrated the effects on the usual buffet characteristics, especially on the shock location and the separation areas on the wing suction side. Using these results, a closed loop control methodology based on a quasi-static approach was defined and several architectures were tested for various parameters such as the input signal, the objective function, the tuning of the feedback gain... All closed loop methods were implemented on a dSPACE device calculating in real time the fluidic actuators command from the unsteady pressure sensors data. The efficiency of delaying the buffet onset or limiting its effects was demonstrated using the quasi-static closed loop approach and tested in both research and industrial wind tunnel environment.