ON THE STABILITY OF ANTISYMMETRIC MOTIONS OF A SHIP EQUIPPED WITH PASSIVE ANTIROLLING TANKS

Until now, the effectiveness of passive antirolling devices, such as tanks, has been checked against the build-up of a large amplitude synchronised rolling motion in monochromatic or narrow band sea. Recently, the authors have shown that this effectiveness extends also in a general stochastic and short crested sea from any direction. Through the use of a perturbation method, they have also proved that it extends to the so called parametric rolling, i.e. to subharmonic rolling that can be excited as a result of the coupling of heave and toll in longitudinal sea from the stern. The effect of the tanks is to increase the threshold for the onset of subharmonic rolling at least in the first region of instability that was investigated in a second order approximate analysis. Numerical simulation confirms this trend. Recent approaches to stability assessment seem to pay an increasing importance to the simultaneous occurrence of instability in the antisymmetric motions sway, yaw and roll, and synchronism with the external loss of control in waves and, probably, broaching-to. In this paper, the stability boundaries as regards the antisymmetric motions are computed for a ship considering the eigenvalues of the system of equations describing the coupled sway, yaw, roll, tanks motions. The results indicate that passive tanks properly adjusted to avoid large amplitude rolling in a beam sea, can play an important role also in reducing the range of instability of these motions.

• Supplemental Notes:
  • STAB 90, Stability of Ships & Ocean Vehicles; 4th Intl Conf; 24-28 Sept 1991; Naples, Italy. Sponsored & Publ by Dept Naval Engng, Univ Naples et al. Procs, v 2, p 401 [8 p, 10 ref, 6 fig]
• Authors:
  • Francescutto, A
• Publication Date: 1991

Language

• English

Subject/Index Terms

• TRT Terms: Ship motion; Stability (Mechanics)
• Old TRIS Terms: Antirolling tanks
• Subject Areas: Marine Transportation;

Filing Info

• Accession Number: 00701044
• Record Type: Publication
• Source Agency: British Maritime Technology
• Files: TRIS
• Created Date: Aug 14 1995 12:00AM