Influence of Downflooding on Iroquois Class Damage Stability

摘要

This report examines stability in waves of a damaged Iroquois class ship. Stern asymmetric flooding is the limiting design case for the Iroquois class. To reduce heel angle for this limiting case, DND is considering installing ports to permit downflooding to lower compartments, resulting in a lower center of gravity for the damaged ship. The computer program FREDYN has been used to examine motions in waves for the damaged ship with and without downflooding. In calm water and moderate sea states, the maximum roll angle occurs during transient motions immediately after damage. These transient motions are not included in current stability criteria. Downflooding significantly reduces the static list of the damaged ship in calm water; however, the initial roll transient that occurs immediately after damage is not significantly influenced by downflooding. For the damaged ship in higher sea states, FREDYN simulations indicate that allowing downflooding gives somewhat reduced roll motions. The FREDYN program appears promising for assessing performance of damaged ships in waves. Further development efforts should be directed toward program validation, robustness, and visualization capabilities.