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Parametric Roll Susceptibility

Screening criterion - parametric roll likely if wave length λ ≈ L_pp AND encounter period 2·T_φ (twice natural roll period).

WeatherRoll
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Formula, assumptions, and limits

Risk=(0.8λ/L1.2)(0.9Te/2Tϕ1.1)\text{Risk} = (0.8 \leq \lambda/L \leq 1.2) \land (0.9 \leq T_e / 2T_\phi \leq 1.1)
SymbolMeaningUnit
λλWave lengthm
LLLBPm
TϕT_\phiNatural roll periods
TeT_eWave encounter periods

Source: IMO MSC.1/Circ.1228; IMO Second-Generation IS criteria

In short

Screening criterion - parametric roll likely if wave length \u03bb \u2248 L_pp AND encounter period 2\u00b7T_\u03c6 (twice natural roll period).

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