At first, the simulation framework had to be adapted for the compound configuration, including an extension of the coupling interface to the Airbus Helicopter’s tool GHOST. Within less than half a year, the simulation was up and running, such that production simulations of the full configuration could be started and results analysed afterwards, in order to support further development of the compound demonstrator as quickly as possible. During several geometry updates, flight mechanical analyses were accomplished and transferred to the topic leader for further consideration in the development process. Within the first period, of primary interest were download factors on the wings, especially in hover, and flight stability, with focus on autorotation and other critical flight states, like slow lateral flight. Later on, further interference phenomena were more of a target.
In another work package acoustic analysis of the rotorcraft started with focus on interference phenomena between the main rotor and propellers and the interaction of the sound generated there with the airframe. The tool chain has shown the capability to represent proper directivities due to shading and reflection effects, and the post-processing of aerodynamic results is quite straightforward.
In total more than a hundred million core hours of computing time have been utilised for over 50 flight states covering the most interesting parts of the full flight envelope. The second reporting period has seen some tool chain enhancements, improving computational efficiency by utilizing automatic mesh refinement and more conservative load evaluations. In addition, several simulations on the X³ demonstrator validated the computational framework for compound helicopters. For the RACER configuration itself, after another loft update many new flight states were run and analyzed aerodynamically as well as acoustically, pinpointing the topic leader at areas requiring more attention and eventual optimization opportunities.
For dissemination, three presentations were held at AHS conferences and another one at the European Rotorcraft Forum in Delft, The Netherlands. The latter one was recognized with the Gareth Padfield Best Young Paper Award for its outstanding contribution to the field of rotorcraft aeromechanics. Another contribution for this year's AHS conference has been accepted, but shifted to October due to the Corona pandemia. Three articles have been published in reviewed journals (2*AHS Journal, 1*CEAS Aeronautical Journal), another one accepted for publication in the AHS Journal. This year's AHS conference paper is intended to be published as an article in the AHS Journal as well, and the tree PhD candidates having worked on the project are currently busy finalizing their dissertations on the findings and insight from the CA³TCH project. The extended tool chain has been implemented at and licensed to Airbus Helicopters, the Topic Leader.
