Over the past fifteen years much progress has been made in BVI (Blade Vortex Interaction) noise prediction. However most of the codes developed over this period of time were restricted to steady flight conditions in order to simplify the physics of the phenomenon. Recently the growing public demand for more stringent noise regulations has led the rotorcraft industry to develop innovative procedures of approach in order to reduce BVI noise in the vicinity of urban areas. The most promising procedures often include decelerations or changes in the descent slope and introduce non stationary flight conditions. A computational tool predicting the dynamics, aerodynamics and acoustics of a rotor in such unsteady conditions was needed, that is why ONERA developed a new complete computation chain able to study unsteady flight conditions. The paper describes this new computational tool. Applications to a low noise flight procedure and a transient maneuver demonstrates its capabilities. For each application a thorough analysis of the noise directivity and levels is conducted. The wake evolution is also considered in order to get a better understanding of the unsteady phenomena at stake. It has been demonstrated that transient maneuvers can generate strong BVI affecting both noise levels and directivity. The maneuver under study exhibited a noise increase of 10 dB during the transient phase. Such a rise of noise would have been deleterious for the helicopter stealth or for public acceptance. Consequently, to address both these issues, it seems important to study maneuvering noise and not to focus only on steady flight configurations as it had been done in the past.


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    Title :

    A new aerodynamic & acoustic computation chain for BVI noise prediction in unsteady flight conditions


    Additional title:

    Ein neues gekoppeltes aero-akustisches Berechnungsverfahren zur Vorhersage von BVI-Geräuschen bei instationären Flugbedingungen


    Contributors:

    Published in:

    Publication date :

    2004


    Size :

    11 Seiten, 14 Bilder, 9 Quellen


    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English







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