Aeroelastic Modeling Effect in Rotor BVI Noise Prediction

The acoustic field generated by a helicopter main rotor experiencing blade-vortex interaction (BVI) during a descent flight path is examined. The prediction procedure starts from the determination of the aeroelastic steady periodic solution. Then, a boundary integral formulation for the velocity potential suited for configurations where stong wake/blade impingement occurs is applied. It is fully three-dimensional, can be applied to blades with arbitrary shape and motion and performs the calculation of both wake shape and blade pressure field. Finally, the noise field generated by the helicopter rotor is evaluated through an aeroacoustic tool based on the Ffowcs Williams and Hawkings equation. The numerical investigation discusses the sensitivity of BVI noise prediction on the aeroelastic models applied for the calculation of blade steady periodic deformations. The eects of the dierent blade deformations given by the aeroelastic solvers considered are examined both in terms of local acoustic signatures and in terms of noise radiation characteristics.

[1]  Giovanni Bernardini,et al.  A Novel Potential-Flow Boundary Integral Formulation for Helicopter Rotors in BVI Conditions , 2005 .

[2]  Berend G. van der Wall,et al.  HART-II: Prediction of Blade-Vortex Interaction Loading , 2003 .

[3]  Massimo Gennaretti,et al.  Aeroelastic Modeling and Vibratory Load Analysis of Helicopters , 2004 .

[4]  F. Farassat.  Linear Acoustic Formulas for Calculation of Rotating Blade Noise , 1981 .

[5]  Earl H. Dowell,et al.  Nonlinear equations of motion for the elastic bending and torsion of twisted nonuniform rotor blades , 1974 .

[6]  D. H. Roberta. Hodges,et al.  Stability of elastic bending and torsion of uniform cantilever rotor blades in hover with variable structural coupling , 1976 .

[7]  Massimo Gennaretti,et al.  Boundary Integral Equation Methods for Aerodynamics , 1992 .

[8]  Berend G. van der Wall,et al.  The HART-II Test: Rotor Wakes and Aeroacoustics with Higher-Harmonic Pitch Control (HHC) Inputs - The Joint German/French/Dutch/US Project , 2002 .

[9]  Luigi Morino,et al.  A General Theory of Unsteady Compressible Potential Aerodynamics , 1974 .

[10]  F. Farassat,et al.  The Uses and Abuses of the Acoustic Analogy in Helicopter Rotor Noise Prediction , 1987 .

[11]  D. L. Hawkings,et al.  Sound generation by turbulence and surfaces in arbitrary motion , 1969, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[12]  Berend G. van der Wall,et al.  The HART II test – measurement of helicopter rotor wakes , 2004 .