Real-Time Simulation of Rotorcraft Downwash in Proximity of Complex Obstacles using Grid-Based Approaches

This paper describes the development and verification of a model for real-time simulation of rotorcraft downwash. Downwash gains importance in rotorcraft flight close to terrain and obstacles where strong aerodynamic forces may act on nearby persons and objects. In areas of loose soil composition, it may further entrain dust or snow and cause dense clouds degrading the pilot's vision (Brownout/Whiteout). Taking into account these effects in training simulation is necessary to prepare pilots and crews for critical situations. The developed methods open up the possibility to capture complex boundary conditions and to calculate rotorcraft- and flight-state specific flow fields underneath rotorcraft at low-level flight. In contrast to existing approaches, recognition of boundary conditions is performed at simulation run-time using ray-tracing algorithms. Thus, the model's grid-based flow field calculation is able to incorporate arbitrary dynamic obstacles and their effect on the downwash. Output of the model can be used for high-fidelity Brownout/Whiteout simulation and for the determination of fluid forces acting on personnel and objects.