Parametric Roll Susceptibility
Screening criterion - parametric roll likely if wave length λ ≈ L_pp AND encounter period 2·T_φ (twice natural roll period).
λ / L
0.92 -
T_e / (2·T_φ)
0.98 -
Risk
HIGH RISK - parametric roll triggering conditions
Formula, assumptions, and limits
IMO MSC.1/Circ.1228 and IMO Second-Generation Intact Stability criteria. Parametric roll is excited when the hull oscillates vertically at twice the roll frequency in head/following seas. Most dangerous for fine hulls - container ships and car carriers.
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| Wave length | m | weather observation | |
| LBP | m | particulars | |
| Natural roll period | s | inclining / observation | |
| Wave encounter period | s | calc from ω_e |