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

LBPmNatural roll periodsObserved wave lengthmEncounter periods

λ / L: 0.92 -

T_e / (2·T_φ): 0.98 -

Risk: HIGH RISK - parametric roll triggering conditions

Changing the inputs requires JavaScript. The calculator above shows its default inputs and result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

\text{Risk} = (0.8 \leq \lambda/L \leq 1.2) \land (0.9 \leq T_e / 2T_\phi \leq 1.1)

Symbol	Meaning	Unit
$λ$	Wave length	m
$L$	LBP	m
$T_\phi$	Natural roll period	s
$T_e$	Wave encounter period	s

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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