Sound generation and radiation from rotor tip-vortex pairing are calculated numerically. Wake geometries of a two-bladed rotor in axial flights are calculated using a time-marching free-wake method without a nonphysical model of the far wake. The acoustic field can be obtained using acoustic analogy. To show the accuracy of the flow calculation scheme, the tip-vortex geometries of the present calculation are compared with those done in the previous publication of a small-scaled rotor experiment. The accuracy of the vortex sound calculation scheme is validated by comparing its numerical and the analytic solution of circular vortex-ring interaction. The tip-vortex pairing consists of a turn of the tip-vortex from one blade rolling around the tip-vortex from the other blade. The tip-vortex pairing amplifies the noise and generates new dominant frequencies. The tip-vortex pairing noise has a quadrupole directivity pattern, and it is especially dominant in the direction of the rotation axis. The peak components of the noise spectrum represent the pairing period and an instability mode.


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    Title :

    Sound generation and radiation from rotor tip-vortex pairing phenomenon


    Additional title:

    Schallerzeugung und Schallabstrahlung durch Paarbildung von Rotorspitzenwirbeln


    Contributors:

    Published in:

    AIAA Journal (online) ; 44 , 6 ; 1181-1187


    Publication date :

    2006


    Size :

    7 Seiten, 14 Bilder, 17 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English




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