Accession Number : ADA019196

Title :   The Effects of Vortex Coherence, Spacing, and Circulation on the Flow-Induced Forces on Vibrating Cables and Bluff Structures.

Descriptive Note : Interim rept.,

Corporate Author : NAVAL RESEARCH LAB WASHINGTON D C

Personal Author(s) : Ramberg,S. E. ; Griffin,O. M.

Report Date : 02 JAN 1976

Pagination or Media Count : 36

Abstract : The vortex wake of a vibrating flexible cable was studied by means of velocity measurements and correlation, frequency spectra, and flow visualization. Three distinct spanwise regimes were identified according to wake structure. Near the cable nodes the flow resembles that of a stationary cable. Adjacent to the node is a transition regime which extends up to the locked-in or synchronized wake flow about the cable antinode. Each regime was characterized by spectral content, degree of spanwise correlation, and local vortex street geometry. Measured downstream velocity profiles and vortex spacing were matched with a mathematical model to obtain the vortex strength and its relation to cable vibration conditions. The von Karman drag formula was used to compute the steady drag coefficients directly, and the distributions of fluctuating lift and drag were inferred from the data. The vortex strength and fluid forces on the vibrating cable were found to be as much as 65 percent larger for locked-in conditions than in the stationary case. Where comparisons were possible, there was good agreement between present results and previous results for vortex-excited rigid cylinders, including some direct measurements of the increased drag. (Author)

Descriptors :   *Vortices, *Mechanical cables, *Blunt bodies, *Wake, Wind tunnel tests, Flow fields, Vibration, Correlation techniques, Flowmeters, Flow visualization, Mooring, Laminar flow, Turbulent flow, Force(Mechanics), Hydrodynamics, Drag, Mathematical models

Subject Categories : Machinery and Tools
      Test Facilities, Equipment and Methods
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE