A MATHEMATICAL METHOD OF DETERMINING HYDRODYNAMICALLY INDUCED FORCES ON A SEMISUBMERSIBLE

In this paper an approximative method is presented with which those hydrodynamic forces (added mass and damping) and wave-excited forces can be determined which have to be known in order to be able to calculate the motions and strength of semisubmersible platforms which are still in the design stage. The method is based on the assumptions that the underwater construction can be subdivided into elements such as spheres, ellipsoids, and cylinders of which the added mass and viscous damping are known. These elements are chosen such that the dimensions are sufficiently small for the relative-motion concept to be applicable. This concept can be used to determine the wave-excited forces if the added mass and damping of the body (element) are known. Using a second assumption, namely that the hydrodynamic forces (added mass and damping) and the wave-excited forces on each element are unaffected by the neighboring elements, the total forces on the platform are found by summation over the elements. From the good agreement between the results of model tests and those of the calculations it can be concluded that reliable results are obtained from the calculations. Consequently the results of the calculation method can be used to determine the behavior of a platform in waves. The influence of water depth, wave direction, draft, and stability on the platform motions in waves can be analyzed systematically. Therefore, alterations in the platform dimensions, aimed at adapting the platform to the location or the weather conditions in which the platform will be operating, can be incorporated during the design stage.

• Supplemental Notes:
  • Presented at the Annual Meeting of SNAME, November 11-12, 1971.
• Corporate Authors:

  Society of Naval Architects and Marine Engineers

  601 Pavonia Avenue
  Jersey City, NJ  United States  07306-2907
• Authors:
  • Hooft, J P
• Publication Date: 1971-11

Media Info

• Features: Appendices; Figures; References; Tables;
• Pagination: 36 p.

Subject/Index Terms

• TRT Terms: Coefficients; Force; Hydrodynamic pressure; Mass; Offshore drilling platforms; Semisubmersibles; Waves
• Old TRIS Terms: Added mass; Hydrodynamic forces; Wave forces on structures
• Subject Areas: Marine Transportation; Materials; Vehicles and Equipment;

Filing Info

• Accession Number: 00028635
• Record Type: Publication
• Source Agency: Society of Naval Architects and Marine Engineers
• Report/Paper Numbers: Paper 1
• Files: TRIS
• Created Date: Apr 10 1972 12:00AM