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VIBRATORY DYNAMICS OF FLOW-EXCITED STRUTS IN WATER

The general problem of the response of a cantilevered beam to flow over its surface is considered experimentally and theoretically. The measured flow induced modal vibratory motion of a nonsinging beam is compared to theoretical estimates of inflow turbulence excitation and boundary-layer excitation. The comparison indicates that while the response to turbulent inflow is dominant at low frequencies, the response of the strut to its own boundary layer is important at high frequencies. The magnitude of hydrodynamically induced damping is also characterized experimentally. It is shown that results agree favorably with an approximate expression based on finite-aspect-ratio, unsteady airfoil theory. Loss factors, based on entrained mass, are found to be inversely proportional to a reduced frequency based on the width of the strut and inflow speed. Finally, a wind tunnel study of the statistical properties of the boundary layer formed on the strut is described. The results disclose that flow separation at the leading edge, which is sensitive to angles of attack, generates a low-frequency pressure field that is markedly higher than that normally encountered in boundary layers. At high frequencies the pressure field is influenced by the local flow parameters normally used in boundary-layer studies.

  • Corporate Authors:

    Naval Ship Research and Development Center

    Ship Acoustics Department
    Bethesda, MD  United States  20034
  • Authors:
    • Blake, W K
    • Maga, L J
  • Publication Date: 1973-12

Media Info

  • Features: References;
  • Pagination: 73 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00052134
  • Record Type: Publication
  • Source Agency: Naval Ship Research and Development Center
  • Report/Paper Numbers: #4087 R&D Rpt
  • Files: TRIS
  • Created Date: Apr 26 1974 12:00AM