Prediction of BVI noise radiation variation due to HHC using advanced prescribed wake methodology

DLR’s comprehensive isolated rotor code S4 is validated with a variety of wind tunnel experimental data from the HART II test of 2001 (Bo105 hingeless Mach-scaled model rotor) at low speed with and without higher harmonic control (HHC) using 3/rev control frequency in descending flight, known to generate strong BVI. To evaluate noise radiation, a coupled S4 and an analytic far field prediction method based on an integral Ffowcs-Williams and Hawkings approach are conducted. Overall, the quality of elasto-mechanical computations, aerodynamic section loads prediction, simulation of the wake geometry and the noise radiation is predicted to a good accuracy, validating the approach of reduced order modeling.

[1]  John C. Houbolt,et al.  Differential equations of motion for combined flapwise bending, chordwise bending, and torsion of twisted nonuniform rotor blades , 1957 .

[2]  J. Delfs,et al.  Improvement of DLR rotor aeroacoustic code (APSIM) and its validation with analytical solution , 2003 .

[3]  van der Wall,et al.  Analytic Formulation of Unsteady Profile Aerodynamics and its Application to Simulation of Rotors , 1992 .

[4]  Berend G. van der Wall,et al.  The HART II international workshop: an assessment of the state-of-the-art in comprehensive code prediction , 2013 .

[5]  Herbert Wagner.  Über die Entstehung des dynamischen Auftriebes von Tragflügeln , 1925 .

[6]  F. Farassat,et al.  An Analytical Comparison of the Acoustic Analogy and Kirchhoff Formulation for Moving Surfaces , 1997 .

[7]  F. Micheli,et al.  Higher harmonic Control Aeroacustic Rotor Test (HART) - Test Documentation and Representative Results , 1996 .

[8]  T. Theodorsen.  General Theory of Aerodynamic Instability and the Mechanism of Flutter , 1934 .

[9]  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.

[10]  W. R. Splettstoesser,et al.  The HELINOISE Aeroacoustic Rotor Test in the DNW , 1993 .

[11]  G. Niesl,et al.  Experimental results of the European HELINOISE aeroacoustic rotor test , 1995 .

[12]  Berend G. van der Wall,et al.  Free-Wake Analysis on Massively Parallel Computers and Validation with HART Test Data , 1997 .

[13]  Berend G. van der Wall,et al.  Aerodynamics and Acoustics of Rotor Blade-Vortex Interactions , 1995 .

[14]  Berend G. van der Wall,et al.  Extensions of prescribed wake modelling for helicopter rotor BVI noise investigations , 2012 .

[15]  S. R. Ahmed,et al.  AERODYNAMICS AND AEROACOUSTICS OF HELICOPTER MAIN-ROTOR/TAIL-ROTOR INTERACTION , 1999 .

[16]  Berend G. van der Wall,et al.  DLR’s S4 Rotor Code Validation With HART II Data: The Baseline Case , 2007 .

[17]  O. Dieterich,et al.  Stall Effects and Blade Torsion - An Evaluation of Predictive Tools , 1999 .

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