High frequency microphone measurements for transition detection on airfoils

Mads Døssing

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    Abstract

    Time series of pressure fluctuations has been obtained using high frequency microphones distributed over the surface of airfoils undergoing wind tunnel tests in the LM Windtunnel, owned by ’LM Glasfiber’, Denmark. The present report describes the dataanalysis, with special attention given to transition detection. It is argued that the transition point can be detected by observing the increase in the mean of the Fourier spectre and that thismethod is very stable froma numerical point of view. Other important issues are also discussed, e.g. the variation of pressure standard deviations (sound pressure) and Tollmien-Schlichting frequencies. The tests were made at Reynolds and Mach numbers corresponding to the operating conditions of a typical horizontal axis wind turbine (HAWT). The Risø B1-18, Risø C2-18 and NACA0015 profiles were tested and the measured transition points are reported.
    Original languageEnglish
    Place of PublicationRoskilde
    PublisherDanmarks Tekniske Universitet, Risø Nationallaboratoriet for Bæredygtig Energi
    Number of pages24
    ISBN (Print)87-55-03674-0
    Publication statusPublished - 2008
    SeriesDenmark. Forskningscenter Risoe. Risoe-R
    Number1645(EN)
    ISSN0106-2840

    Keywords

    • Risø-R-1645
    • Risø-R-1645(EN)

    Cite this

    Døssing, M. (2008). High frequency microphone measurements for transition detection on airfoils. Danmarks Tekniske Universitet, Risø Nationallaboratoriet for Bæredygtig Energi. Denmark. Forskningscenter Risoe. Risoe-R, No. 1645(EN)