Validation of Aerodynamic and Aeroacoustic Simulations of Contra-Rotating Open Rotors at Low-Speed Flight Conditions

Contra Rotating Open Rotor (CROR) propulsion systems have been the focus of a number of research projects in recent years, aiming to establish this propulsion system as an economic and environmentally friendly powerplant for future transport aircraft. In the frame of the EU 7th Framework Joint Technology Initiative Smart Fixed Wing Aircraft project, the DLR Institute of Aerodynamics and Flow Technology is participating as an associated partner in the Airbus-led studies of the Contra-Rotating Open Rotor. Due to significant technical challenges in terms of noise emissions, installation effects and certification that still need to be addressed, the numerical activities require the use of sophisticated multidisciplinary analysis tools and approaches covering both aerodynamics and aeroacoustics. Having been widely applied to the simulations of single as well as contra-rotation propellers, the DLR CFD code TAU and the aeroacoustic analysis tool APSIM+ allow for a detailed analysis and an improved understanding of the complex aerodynamics and aeroacoustics of this type of propulsion system. Drawing benefit from a set of high- quality results from aeroacoustic wind tunnel tests of a generic Airbus designed CROR configuration, this paper will present an in-depth analysis and validation of the DLR numerical approach to coupled CFD-CAA-simulations to enable reliable predictions of the aerodynamic and aeroacoustic performance of CROR propulsion systems.