Analysis and control of unsteady transonic flow over 2D and 3D aeroelastic wing configurations

• Applicant: Dr.-Ing. Deepak Prem Ramaswamy
• Subject Area: Fluid Mechanics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 548378806

Modern transport aircraft typically cruise in the transonic flow regime, which is inherently non-linear due to the presence of shock waves and shock-induced separations. At conditions close to the edge of the flight envelope, flow instability called transonic buffet develops, characterised by a periodic self-sustained oscillation of the shock over the wing surface and accompanied by a massive unsteady flow separation. Moreover, modern wing structures are increasingly designed to be lightweight and elastic; the unsteady aerodynamic buffet loads can excite the surface and lead to unfavourable structural oscillations (buffeting). This results in a complex fluid-structural interaction, causing undesirable aeroelastic effects that deviate from a pure rigid-body analysis. Therefore, characterisation and understanding of the coupled dynamics of the fluid and structural system are crucial to improving the structural lifespan and the operational flight envelope of transport aircraft. The prerequisite for this is a fundamental analysis of buffet mechanisms on both structurally rigid and aeroelastic wing configurations with a systematic increase in complexity from full-span 2D geometries to 2D finite wings and eventually to 3D swept wing geometries. Furthermore, the adverse nature of this phenomenon calls for a suitable control strategy to reduce the detrimental effects of buffet and buffeting. This research project investigates air-jet vortex generators (AJVGs) as a promising strategy for buffet control on rigid and aeroelastic wing structures. In this technique, the vortices injected by the air-jet injection into the crossflow energise the boundary layer and improve the boundary layer’s resistance to shock-induced separation. While previous parametric studies on AJVGs provide the necessary insight to select suitable configurations for buffet control on rigid wings, buffet control on more complex configurations has not been investigated, and the mechanisms are poorly understood. The overall goals of this research project are thus (a) to understand the mechanisms governing unsteady transonic buffet phenomenon over rigid and aeroelastic wing configurations and (b) to develop a suitable control strategy using AJVGs to alleviate or eliminate unfavourable buffet-induced effects over such wings. For this, detailed experiments will be carried out to generate high-quality datasets using state-of-the-art optical measurement tools. This includes a simultaneous acquisition of fluid velocities and structural deformations at high temporal resolution to investigate the coupled aerodynamic and structural systems. Furthermore, advanced post-processing techniques will be applied to characterise the dynamic flow phenomenon and the behaviour of turbulent structures. As a result, this research project is expected to significantly contribute to the fundamental understanding of mechanisms governing transonic buffet and buffeting along with effective means to control them.

• DFG Programme: WBP Position