CAA-NLH · Theories and Numerical code for prediction of near and far field noise generated by new generation propellers and Open Rotor blades

The inherently high propulsive efficiency of advanced propellers and Counter-Rotating Open Rotors (CROR) have a great potential for fuel savings, but the level of noise emitted by the open blades represent a major obstacle to their environmental acceptance. Consequently, the design of a low noise, fuel efficient open rotor powerplant is one of the major objectives of the CleanSky JTI. Within the virtual prototype design environment, the availability of highly efficient calculation procedures of noise sources and their propagation are essential to achieve these objectives. While the CAA approach for the acoustic far-field noise propagation is well established, the critical issue remains the delivery of fast and accurate unsteady CFD-solutions for prediction of the noise sources. The present CAA-NLH proposal responds to this objective, through an advanced new approach for the CFD determination of the noise sources. The CAA-NLH project will rely on the nonlinear harmonic method (NLH) which allows a gain in CPU performance for CROR’s compared to current CFD sliding grid or Chimera methodologies, of two to three orders of magnitude. This method, defined in the frequency domain, has been largely validated and successfully applied on multistage turbines and compressors at many companies. Its extension to propeller and CROR configurations has recently been initiated. The present project proposes the further extension of this approach, including a dedicated post-processing of the pressure fluctuations to determine the near-field tone noise, and an integration of the proposer’s FW-H module with the NLH code for reliable far-field noise predictions, including automatic CFD/FW-H coupling (with automatic CFD grid generation), optimized generation of permeable surfaces and experimental validation, with a turnaround time for a complete simulation of a few hours on a low number of processors. A professional, user friendly and quality assured software environment will be pursued.