Investigation of a simplified aerodynamic modelling technique for noise predictions using FW–H propagation

This paper addresses the influence of the elastic rotor blade deformation and the aerodynamic interference from the fuselage on the rotor aerodynamics, including rotor noise characteristics. A BO105 main rotor/fuselage configuration is chosen for the numerical simulations. An unsteady aerodynamic code based on free wake three-dimensional panel method (UPM) is used to account for nonlinear effects associated with the mutual interference between main rotor and fuselage. Airbus Helicopters’ (formerly: Eurocopter) rotor code (HOST) is coupled with this aerodynamic code (UPM) to account for the effect of elastic blade deformation. The effect of the fuselage is simulated using two fuselage models in aerodynamic code, (1) potential theory in the form of a panelized fuselage and (2) an analytic fuselage influence formulation derived from isolated fuselage simulation. The advantage of (2) is in its computational efficiency. The aerodynamic modelling is then coupled with an aero-acoustic post-processing tool based on the Ffowcs-Williams–Hawkings (FW–H) approach for evaluating the noise propagation to the far-field. This toolchain is then evaluated in different flight conditions to assess the usability of this approach in the design process. In descending flight, the acoustic prediction is completed at a very mature level, as the blade vortex interaction is well captured. In climb, the major noise peak is underpredicted, while the overall directivity agreement is well matched. In forward flight, due to a phase shift in the airloads prediction, parts of the loading noise directivity are not well captured. The onset of transonic effects further degrades the results obtained at the front of the rotor. For the investigated flight cases, the analytical fuselage formulation brought very similar results to the panelized fuselage model, therefore proving its worthiness for further accelerating the simulation in these flight conditions.

[1]  H. Sugawara,et al.  Construction and validation of an analysis tool chain for rotorcraft active noise reduction , 2012 .

[2]  Berend G. van der Wall,et al.  The EU HeliNOVI project - Wind tunnel investigations for noise and vibration reduction , 2005 .

[3]  Ewald Krämer,et al.  Aeroelastic Simulations of Isolated Rotors Using Weak Fluid-Structure Coupling , 2007 .

[4]  Jochen Raddatz,et al.  Block Structured Navier-Stokes Solver FLOWer , 2005 .

[5]  Berend G. van der Wall,et al.  Acoustic wind tunnel tests on helicopter tail rotor noise (HeliNOVI) , 2008 .

[6]  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.

[7]  Berend G. van der Wall,et al.  A Comprehensive Rotary-Wing Data Base for Code Validation: The HART II International Workshop , 2011 .

[8]  Berend G. van der Wall,et al.  The HART II international workshop: an assessment of the state of the art in CFD/CSD prediction , 2013 .

[9]  W. von Grünhagen,et al.  HOST, a General Helicopter Simulation Tool for Germany and France , 2000 .

[10]  Heinrich G. Jacob,et al.  Rechnergestützte Optimierung statischer und dynamischer Systeme , 1982 .

[11]  S. R. Ahmed,et al.  Helicopter Main-Rotor/Tail-Rotor Interaction , 2000 .

[12]  J. Yin,et al.  Prediction - and its validation - of the acoustics of multiblade , 1994 .

[13]  S. R. Ahmed Unsteady Panel Method Calculation of Pressure Distribution on BO 105 Model Rotor Blades and Validation with DNW-Test Data , 1994 .

[14]  Berend G. van der Wall,et al.  Semi-Empirical Physics-Based Modeling of Fuselage-Rotor and Fuselage-Wake Interferences for Comprehensive Codes , 2014 .

[15]  Berend G. van der Wall,et al.  Semi-empirical modeling of fuselage–rotor interference for comprehensive codes: the fundamental model , 2014 .

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

[17]  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 .

[18]  James D. Baeder,et al.  An Assessment of Comprehensive Code Prediction State-of-the-Art Using the HART II International Workshop Data , 2012 .

[19]  Berend G. van der Wall,et al.  REPRESENTATIVE TEST RESULTS FROM HELINOVI AEROACOUSTIC MAIN ROTOR/TAIL ROTOR/FUSELAGE TEST IN DNW , 2005 .