To fulfil the SFWA objectives of reduced engine noise, a major effort was required towards innovative noise control methodologies and improved predictive capability of the CFD/CAA software systems.

The present project combined an experimental investigation of two, low TRL flow/noise control options, associated with an innovative and highly efficient numerical CFD/CAA approach:

• On the experimental side, the first noise control method, based on porous treatment of the blades, was tested in an anechoic facility. The associated acoustic impedance was determined as input for the CFD/CAA approach. The second concept relied on active blade surface to control the front rotor wake by actuators on the front rotor blade, possibly DBD plasma actuators. The wake characteristics behind the actuated blades were tested in a cascade facility.
• On the numerical side, the DINNO-CROR proposal was based on an advanced new approach for the CFD determination of the noise sources and on the acoustic analogy for far-field noise propagation.

While the CAA approach relied on a time domain formulation of the FW-H equations, the critical issue remained to deliver fast and accurate unsteady CFD-solutions for prediction of the noise sources.

The DINNO-CROR project applied the nonlinear harmonic method (NLH) which allows a gain in CPU compared to current CFD methodologies, of close to three orders of magnitude. This method had been largely validated and applied on multistage turbines and compressors, and its extension to CROR’s had recently been initiated.

In the project it was further extended to include the physics of the investigated noise control systems. In TASK 2, the NLH methodology was extended to model the interaction of the rotor with the pylon. For Concept 1, the boundary layer absorption was modelled by introducing an impedance boundary conditions on the pylon; while for Concept 2, the non-radial pylon was modelled directly as a solid surface.