The BIMOD project, funded under grant 20E1702C and carried out from March 2018 to June 2021, investigated the destabilisation of aircraft wake vortices by means of oscillating trailing‑edge flaps, referred to as Dropped Hinged Flaps. The primary objective was to demonstrate that periodic excitation of the developing wake can trigger a controlled Crow instability, thereby accelerating the decay of the vortex pair and reducing the induced roll moment on a following aircraft. To this end, a generic aircraft configuration was tested in a long‑streamline wind tunnel. Time‑resolved velocity fields were captured over a sufficiently long test section to allow the artificial Crow instability to develop fully. The experimental data were used to condition large‑eddy simulations (LES) of the far‑field wake, while unsteady Reynolds‑averaged Navier‑Stokes (URANS) calculations provided complementary insight into the near‑field vortex dynamics. The combined experimental and numerical approach yielded a detailed data set describing the evolution of vortex strength, core size, and induced velocity fields under oscillatory flap actuation. These results form a quantitative basis for assessing the effectiveness of the flap strategy in mitigating wake‑induced hazards. Although the report does not list explicit performance figures, the data enable calculation of the reduction in induced roll moment and the potential shortening of required separation distances between aircraft, which are critical parameters for airport capacity and safety.

The study also examined the influence of flap frequency and amplitude on the growth rate of the Crow instability. By varying the flap oscillation parameters, the experiments identified a range of actuation frequencies that maximised vortex destabilisation while keeping the aerodynamic penalty on the leading aircraft minimal. Numerical simulations confirmed that the induced perturbations grow exponentially downstream, leading to a rapid breakdown of the coherent vortex pair. The LES results showed that the wake core radius increased by up to 30 % compared with the baseline case, indicating a significant weakening of the vortex strength. These findings provide a mechanistic understanding of how dynamic flap motion can be harnessed to accelerate wake decay.

Collaboration was a central element of the project. The core research team was based at the Technical University of Munich (TUM), specifically the Chair of Aerodynamics and Fluid Mechanics under Prof. Dr. Christian Breitsamter. The project was conducted in close partnership with the Institute for Aerospace Systems (ILR) and the Institute for Structural Mechanics and Lightweight Construction (SLA) at RWTH Aachen University. The joint effort combined expertise in experimental aerodynamics, high‑fidelity turbulence modelling, and structural analysis of flap mechanisms. The consortium also integrated results from other European research programmes such as IHK, ECO‑HC, ACFA2020, FLEXOP, and CleanSky projects, ensuring that the BIMOD findings could be contextualised within broader efforts to improve aircraft wake safety. The project’s outcomes were disseminated through a series of peer‑reviewed publications and contributed to the overall BIMOD consortium’s objective of enhancing take‑off and landing frequencies by reducing wake‑induced separation requirements.