Aerodynamics of Helicopter. Application of the Navier-Stokes Codes Developped in the Framework of the Joined German/French CFD Research Project CHANCE

The FLOWer and elsA CFD flow solvers, under development respectively at DLR and ONERA within the joined French-German project CHANCE, are being validated on cases of industrial interest by Eurocopter. The paper has presented the validation of the FLOWer code about the ATR-A rotor of the EC145 helicopter in hovering conditions, and of the elsA software about the Dauphin and NH90 helicopter fuselages in forward flight conditions. Both codes showed a good and robust convergence and in all cases the numerical predictions have showed a satisfactory agreement with the experimental data, e.g. wind tunnel or flight test data. The future validation activities of the FLOWer and elsA codes will focus on isolated rotor in forward flight and helicopter fuselage, with an actuator disk model simulating the main rotor induced flow, in forward flight conditions. In conclusion, thanks to the large progress in CFD tools (numerical model, convergence techniques, parallel computation, etc.) and in computer performance, it is nowadays possible to predict a lot of complex aerodynamic phenomena with enough accuracy and within an acceptable feedback calculation time, i.e. less than 3 days in industrial environment. CFD tools will help investigating some very complex phenomena usually difficult or expensive to analyse with wind tunnel facilities alone. They seem to be mature enough to drive optimization design and thus dramatically reduce development costs, although wind tunnel tests still remain the ultimate judge in confidence