Coupled and Trimmed Aerodynamic and Aeroacoustic Simulations for Airbus Helicopters' Compound Helicopter RACER

Abstract

In recent years, various helicopter manufacturers increasingly have been focusing on the development of new high-speed rotorcraft configurations, one of them being the compound helicopter RACER (rapid and cost-efficient rotorcraft) of Airbus Helicopters (AH). However, these new configurations encounter new aeromechanic challenges, in terms of aerodynamic interactions, flight mechanics stability, rotor dynamics, or aeroacoustic noise emission, to name only a few. To support AH at the minimization of risk of RACER's first flight, the Institute of Aerodynamics and Gas Dynamics provides high-fidelity coupled and trimmed aerodynamic and aeroacoustic simulations of the complete helicopter by the application of a multidisciplinary tool chain. In its first part, the work focuses on the description of this advanced tool chain and on important features for the analysis of this new configuration. In the second part, exemplary simulation results for a hover and a high-speed cruise flight condition are shown, and the main aerodynamic interactions between the different components are identified. As expected for this configuration, numerous interactions are found for both flight cases, e.g., main rotor–propeller interaction in hover or main rotor–wing interaction in high-speed flight. Finally, aeroacoustic results are shown for hover with a close look at the propellers' contribution.

Aerodynamics and flight mechanics analysis of Airbus Helicopters’ compound helicopter RACER in hover under crosswind conditions

“…As previously shown by the authors [20], the unique design of RACER causes a variety of interactions between the additional components. Amongst them, the interference of the main rotor on the lateral rotors is of particular interest for the flight cases investigated here.…”

“…The simulation framework which is being introduced in the following sections was already used for a number of other flight cases of RACER's flight envelope within the same project like, for example, cruise flight at 220 kts [20].…”

“…While research has been conducted on aerodynamics and design of RACER's configuration [18,28,29], these studies used either low-fidelity methods, focused only on limited components or neglected flight mechanics. The most comprehensive approach has been shown by the authors [20], where a multidisciplinary, high-fidelity tool chain for evaluation of aerodynamics, flight mechanics and aeroacoustics of RACER has been presented and has provided substantial insight into aerodynamic interactions of the complete rotorcraft in free-flight.…”

Toward Vehicle-Level Optimization of Compound Rotorcraft Aerodynamics

“…al. [8][9][10][11][12] also performed high-fidelity URANS simulations of the RACER configuration in trimmed hover, cruise flight, and crosswind, using resolved blades for the main rotor and the lateral rotors, with high-order schemes and mesh adaption. Their work focused largely on the overall performance, acoustics, and flight mechanics, but a systematic isolation of components was also conducted to identify the mutual aerodynamic interferences.…”