Pure loss of stability calculation of naval ship in regular waves
(2.Naval Academy of Armament, Beijing, China 100073)
【Abstract】The pure loss of stability of a ship is one of the failure modes of the second-generation intact stability criteria. Based on the static surface coordinate system, the generalized pitch angle and draught variable are defined, and a wave equation with clear physical meaning is deduced. Based on the Froude-Krylov hypothesis, combined with AutoCAD 2D surface area computing technology and the VBA programming method, a calculation method of the loss of pure stability of ships in regular waves is proposed. For a naval ship, the righting arm is calculated in regular waves, and the large heel ship state is shown to have an identical convergence. The results of the calculations show that a significant reduction in the metacentric height of the maximum righting arm occurs not just in a wave crest but also in a trough. By analyzing the wave profile under the hull, it can be clearly seen that wave amplitude above the deck or below the bottom of the hull causes the pure loss of stability, and in oblique waves or beam seas, the pure loss of stability causes the asymmetry of the wave profile on the hull. The coinciding convergence of the calculations shows that the process of the definition of generalized pitch can be employed to assess the pure loss of stability of naval ships in regular waves.
【Keywords】 naval ship; pure loss of stability; regular waves;
KEMPF G. Die stabilitätsbeanspruchung der schiff durch wellen und schwingungen[J]. Werft Reedere Hafen, 1938, 19: 200–202.
PAULLING J R. The transverse stability of a ship in a longitudinal seaway[J]. Journal of Ship Research, 1961, 4 (4): 37–49.
PAULLING J R, KAESTNER S, SCHAFFRAN S. Experimental studies of capsizing of intact ships in heavy seas[R]. U. S. Coast Guard Technical Report, 1972.
GRIM O. Beitrag zu dem problem der Sicherheit des Schiffes im seegang[J]. Schiff und Hafen, 1961, 6: 490–497.
HAMAMOTO M, UMEDA N, SHIGEHIRO R, et al. Transverse stability of a ship in following sea[J]. The Japan Society of Naval Architects and Ocean Engineers, 1982, 185: 49–56.
HAMAMOTO M, KIM Y S, MATSUDA A, et al. An analysis of a ship capsizing in quartering seas[J]. The Society of Naval Architects of Japan, 1992, 172: 135–145 (in Japanese).
HAMAMOTO M, KIM Y S. A new coordinate system and the equations describing manoeuvring motion of a ship in waves[J]. The Society of Naval Architects of Japan, 1993, 173: 209–220 (in Japanese).
FANG M C, LEE C K. On the dynamic stability of a ship advancing in longitudinal waves[J]. International Shipbuilding Progress, 1993, 40 (422): 177–197.
KREUZER E, WENDT M. Ship capsizing analysis using advanced hydrodynamic modelling[J]. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2000, 358 (1771): 1835–1851.
KONG X J, CAO Z H. Calculation of righting arm for ships in quartering seas[J]. Shipbuilding of China, 1994 (2): 32–41 (in Chinese).
XIE W. Research on the draft vulnerability criteria of the pure loss of stability of ship[D]. Dalian: Dalian University of Technology, 2014 (in Chinese).
ZHOU Y H, ZHANG G F, NIU Y X, et al. Study on full-scale ships based on pure loss of stability criteria15[J]. Shipbuilding of China, 2015, 56 (Supp 1): 37–47 (in Chinese).
MA K, GAN E, XIE W. Sample calculations and analysis on vulnerability criteria of pure loss of stability[J]. Shipbuilding of China, 2015, 56 (Supp 1): 193–200 (in Chinese).
HU L F, LU J, GU M. Status analysis of research on ship's stability in waves[J]. Shipbuilding of China, 2015, 56 (Supp 1): 211–216 (in Chinese).
ZHU J, HUANG K L. The calculating method of tow-dimension region for ship stability and damaged-stability[C]//Proceedings of the Ninth National Conference on Maritime Technology. Shanghai: Shanghai Maritime Exchange Association, 2003: 99–104 (in Chinese).