Coherent structure of a magnetically suspended sphere

Taro Yamashita, Satoshi Kikuchi, Takuma Kato, Yasuaki Kohama

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

    Abstract

    Conventional wind tunnel testing has the problems that real phenomena are different from the test environments. One of the problems is the support interference. In conventional testing, the problem that mechanical suspensions may affect the test condition is always present. The solution to the problem is a Magnetic Suspension and Balance System (MSBS). An MSBS can suspend a model in a wind tunnel by using magnetic forces. So an environment where no mechanical suspension exists, can be realized in a test section. In present research, the advantages of MSBS were applied to the measurement of the coherent structures produced behind a sphere. First, in order to verify the advantage of the environment where no mechanical suspension exists, drag coefficients are compared with and without a dummy sting in the MSBS. When the dummy stings were placed closely behind a sphere, the drag of a sphere with dummy sting decreased compared with that without dummy sting. It was due to the reduction of the wake width when dummy sting was put in. After that, the coherent structures in the wake of a sphere were examined using hot wire measurements. The two dominant frequencies were found at Re=3.6×104. One was the lower frequency that is called the very low mode in present paper. The very low mode was suspected to be an axisymmetric structure and to be related to the movement of the recirculation bubble. The other was the low mode, which was common to the low mode of conventional researches. The low mode was quantitatively indicated to be the alternating structure, which fluctuated with the amplitude of about 0.3D in the plane of x/D=3.0 and the wavelength in the freestream direction was about 3.6D.

    Original languageEnglish
    Title of host publicationCollection of Technical Papers - 44th AIAA Aerospace Sciences Meeting
    PublisherAmerican Institute of Aeronautics and Astronautics Inc.
    Pages17000-17013
    Number of pages14
    ISBN (Print)1563478072, 9781563478079
    DOIs
    Publication statusPublished - 2006
    Event44th AIAA Aerospace Sciences Meeting 2006 - Reno, NV, United States
    Duration: 2006 Jan 92006 Jan 12

    Publication series

    NameCollection of Technical Papers - 44th AIAA Aerospace Sciences Meeting
    Volume22

    Other

    Other44th AIAA Aerospace Sciences Meeting 2006
    Country/TerritoryUnited States
    CityReno, NV
    Period06/1/906/1/12

    ASJC Scopus subject areas

    • Space and Planetary Science
    • Aerospace Engineering

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