Acoustic and aerodynamic data from the HELISHAPE experiment have been analyzed to investigate BWI noise in descent flight conditions. Application of appropriate BWI filters to both acoustic and aerodynamic data showed that BWI fluctuations can be divided to Type I and Type II with respect to their origin being impulsive blade vortex interaction or blade turbulence interaction, respectively. Impulsive BVI events come before BWI noise and are not sources of BWI noise, as proposed in the past. Acoustic BWI fluctuation analysis in terms of Struhal number and probability distribution was found to be in agreement with the aerodynamic data analysis and with similar previous analysis on take off flight conditions. The results can be further considered as providing support to the theory that connects BWI noise to elliptic instabilities of corotating vortices. The acoustically dominant BWI region was located to be between 0.85R at 85 deg and 0.62R at 115 deg azimuth. Use of wake charts provided the vortices encountered in that region showing that BWI fluctuations do not come in the region of younger vortices, possibly, because no elliptic instabilities have yet formed. Finally, it was found that the blade tip can affect the Type I fluctuations, but does not affect Type II, which are the fluctuations attributed to blade wake interaction.


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    Title :

    Investigation on rotor blade-wake interaction noise in descent flight conditions


    Contributors:


    Publication date :

    2009


    Size :

    11 Seiten, 13 Bilder, 17 Quellen



    Type of media :

    Conference paper


    Type of material :

    Storage medium


    Language :

    English




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