A model of a floating breakwater made of 0.2-mm thick V-118 chlorovinyl film was tested in wave tanks of the OIIMF laboratory. The plastic film is anchored by four cables and is supported by a pocket of air (at a slight excess pressure) trapped between the film and the water surface. The model profile consists of two flat surfaces, each inclined to the surface at an angle A and joined together above the water in a circular arc. Five 1:40 scale models with A = 20; 30; 45; 60; 90 degrees were tested, and the most promising variant was tested in greater detail at a scale of 1:20. The wave height was measured with a specially designed self-calibrating stringed sensor by using an insulated electrode with periodically spaced exposed rings. Strain gauge dynamometers measured the anchor forces, while modified DBU 50-2 dirigible membrane strain gauges (using constantan wire sensors) measured the forces in the film. Motion pictures supplemented the recordings. The optimum design considering damping, forces, and material consumption has an A = 45 degrees. The anchor force was assumed to consist of a static part Q and a dynamic part (P sin dt), all of which increase with an increasing length, wave height, and excess pressure. The ratio P/Q was found to decrease with increased pressure and wave steepness. The breakwater is effective for wave lengths below 50 m. with a steepness of 1:12. It provide 70 percent damping with an excess pressure of 0.2 atm, and an anchor force 20 T/m with P = (0.2--0.3) Q. It operates chiefly by reflecting the waves from the front surface, and a ballast added to this surface increases its effectiveness.

Media Info

  • Features: Figures;
  • Pagination: p. 130-133
  • Serial:
    • Issue Number: 17

Subject/Index Terms

Filing Info

  • Accession Number: 00014966
  • Record Type: Publication
  • Source Agency: Joint Publications Research Service
  • Files: TRIS
  • Created Date: May 7 1971 12:00AM