In the DLR project CHASER, nine DLR institutes are jointly developing a process chain for the design of helicopters. In parallel, the partners develop a highly accurate calculation method for the evaluation of helicopter rotors. The largely automatic process chain for rotorcraft pre-design first identifies suitable helicopter concepts for the given flight mission, then optimizes the external shape, flight performance, helicopter airframe structure, etc., and finally provides all necessary parameters for virtual testing in the flight simulator. Additionally, cabin design aspects are considered, especially for rescue helicopters. Based on the results in previous projects, three target configurations are considered in CHASER:
All configurations are first designed with the process chain and then tested in the flight simulator.
As a contribution to the project, the scientists of the Institute of Aerodynamics and Flow Technology are developing calculation methods for the aerodynamic evaluation of the helicopters. Depending on the intended use, different methods of different prediction accuracy are applied: For the pre-design of helicopters, aerodynamic calculation results must be available within seconds or a few minutes, so that the automatically running process chain can analyze and optimize a large number of different configurations in a short time. Therefore, simple analytical or empirical formulas are used, as well as panel-freewake calculation methods. The latter allow good computational accuracy for arbitrary helicopter geometries at low computation times.
For the prediction of helicopter aerodynamics DLR uses Computational Fluid Dynamics (CFD) methods, which are tightly coupled with the disciplines flight mechanics and structural mechanics. This allows for accurate simulations of the strong interplay between aerodynamics with pilot inputs and elastic deformation of the rotor blades. In CHASER, the project participants are working on establishing a new coupling chain for the interdisciplinary simulation of helicopters. The CFD method CODA and the helicopter simulation method VAST, which are both newly developed at DLR, as well as the commercial multi-body simulation method Simpack are integrated into this chain for the simulation of aerodynamics, flight mechanics and structural dynamics. Thanks to the modern computational tools and a newly created modularized coupling environment, the range of applications of the simulation methods is to be significantly increased.