Screening criterion - parametric roll likely if wave length λ ≈ L_pp AND encounter period 2·T_φ (twice natural roll period).
Formula
$$ \text{Risk} = (0.8 \leq \lambda/L \leq 1.2) \land (0.9 \leq T_e / 2T_\phi \leq 1.1) $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $λ$ | Wave length | m | weather observation |
| $L$ | LBP | m | particulars |
| $T_\phi$ | Natural roll period | s | inclining / observation |
| $T_e$ | Wave encounter period | s | calc from ω_e |
Sources
- IMO MSC.1/Circ.1228.
- IMO Second-Generation IS criteria.