With the significant reduction of jet-engine noise levels in recent years, airframe noise sources have become increasingly important to overall aircraft noise. For some aircraft, such as the Boeing 777, landing gear can be a dominant airframe noise source, which is generally noted to cover a broad range of frequencies resulting from flow interactions with components that range in size from the order of a millimeter to a meter. Attempts are made to theoretically or computationally determine landing-gear noise characteristics. To further improve computational models of the flow around landing gear, more experimental data are preferred. This study is a follow-on to the two previous studies of Lazos (Lazos, B.S., AIAA Journal Vol. 490, No. 2, 2002, pp. 193-198, and AIAA Journal Vol. 40, No. 12, 2002, pp. 2402-2411). The model used is a simplified four-wheel configuration scaled to 31% to a Boeing 757 main landing gear. Dressings, wheel hubs, brake linings, and cross struts are eliminated. Wind tunnel tests are conducted at a wheel-diameter-based Reynolds number of 6 x 105. Digital particle velocity data are acquired and used to determine the mean velocity components and the Reynolds stresses in the vertical midplane surrounding a set of in-line wheels. The results highlight a region of significant turbulent activity in the gap between the wheels at the ground side of the wheel horizontal midplane. Turbulence production is expected to result from the flow pouring into the gap region from the wing and ground sides of the fore wheel. The mean transverse component of velocity in the gap is noted to be only about 10% of the freestream velocity , but the standard deviation is nearly 70% of the freestream velocity, indicating a highly unsteady region of flow. Transverse flow through the gap from the wing side of the wheels is expected to result from a vertical pressure gradient across the wheels because of blockage created by the center support strut. Gap flow is expected to be even more prominent for fully dressed landing gear because there is more wing-side structure to block the flow.


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    Title :

    Reynolds stresses around the wheels of a simplified four-wheel landing gear


    Additional title:

    Reynoldsspannungen an den Rädern des vereinfachten Modells eines Flugzeugfahrwerks


    Contributors:
    Lazos, B.S. (author)

    Published in:

    AIAA Journal ; 42 , 1 ; 196-198


    Publication date :

    2004


    Size :

    3 Seiten, 4 Bilder, 6 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English