DYNAMIC FORCES EXERTED BY OSCILLATING CABLES

The manner in which the forces applied by a mooring cable to a floating buoy affect (in a linearized sense) the response of that body to regular waves is examined first by considering the case of a vertical, elastic cable of negligible weight density. Seeming infinities are encountered in the cable-alone solutions in view of neglect to the cable-motion-induced hydrodynamic damping forces. Bounded solutions for the buoy-cable system are shown to exist nevertheless. An outline of the treatment of the case of a cable of quite arbitrary scope and combination of parameters is given to demonstrate that the terms contributed by the cable can be identified and studied separately to determine their relative importance. A single set of results for cable force operations is given to show their frequency behavior. Much more numerical experience is needed. Further determinations should be made of cable force operators by measurements of the forces required to oscillate harmonically full-scale cables in a deep river with a known (or measurable) current profile. It is conjectured that, in some cases, cable forces may be approximated by their static force derivations in the wave-length range of interest. Verification of the validity of this conjecture requires examination of computer results for practical ranges of cable parameters. A new derivation of the equations of motion is given in Appendix A. It is found that the fluid added mass effects as given in other developments are incorrect. In addition, it is shown the effect of buoyancy has not heretofore generally been properly included in both the static and dynamic equations. The influence of these corrections on the dynamic response and the static shape requires further numerical evaluations by employing a suitably modified computer program.

  • Corporate Authors:

    American Institute of Aeronautics and Astronautics

    1290 Avenue of the Americas
    New York, NY  USA  10019
  • Authors:
    • Breslin, J P
  • Publication Date: 1974-1

Media Info

  • Features: Appendices; References;
  • Pagination: p. 19-31
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00051872
  • Record Type: Publication
  • Source Agency: American Institute of Aeronautics and Astronautics
  • Files: TRIS
  • Created Date: Apr 9 1974 12:00AM