LOW FREQUENCY HEAVE DAMPING OF SEMISUBMERSIBLE PLATFORMS: SOME EXPERIMENTAL RESULTS

This paper describes results obtained from forced heave experiments (at ENSM) of a 1:40 model of a typical semisubmersible pontoon. The model was built in such a way that different corner shapes could be achieved; sharp (90Deg.) corners, rounded corners, and chamfered (2 x 135Deg.) corners. The experiments covered a wide range of forced amplitudes and frequencies, and they were carried out in both still water and superimposed regular waves. Computations of the added masses and radiation dampings were also performed in order to provide a basis for comparison. Results obtained for the added-mass coefficients have shown globally good agreement between computed and measured values, with a somewhat limited (but still existent) effect of the corner geometry. Measured damping values are given as equivalent drag coefficients (after the calculated radiation damping has been removed), and shown as functions of Kc number and frequency. Corner geometries appear to have a major effect on the obtained Cd values, with typical figures ranging from 4 or 5 (for the square corners) down to less than 1 (for the rounded corners). These results are commented with references to previous theoretical and experimental investigations.

• Supplemental Notes:
  • Procs. of Intl. Conference on Behaviour of Offshore Structures (BOSS '88), held Trondheim, Norway, June 1988, Vol. 2: Hydrodynamics, p. 591 [14 pp., 8 ref., 1 tab., 13 fig., 1 phot.]
• Authors:
  • MARCHAND, E
  • le Berhault, C
  • Molin, B
• Publication Date: 1988

Language

• English

Subject/Index Terms

• TRT Terms: Damping (Physics); Heaving (Ship motion); Semisubmersibles
• Old TRIS Terms: Wave forces on structures
• Subject Areas: Marine Transportation; Vehicles and Equipment;

Filing Info

• Accession Number: 00695071
• Record Type: Publication
• Source Agency: British Maritime Technology
• Files: TRIS
• Created Date: Aug 14 1995 12:00AM