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Froude Number - Hull Speed Regime

Froude number Fn = V/√(g·L) - the dimensionless speed index that determines whether a hull is in displacement, semi-displacement or planing regime.

FroudeSpeedResistance
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Formula, assumptions, and limits

Fn=VgLF_n = \frac{V}{\sqrt{g \cdot L}}
SymbolMeaningUnit
VVSpeed through waterm/s
LLWaterline lengthm

Source: Rawson & Tupper Vol 2

In short

Froude number Fn = V/\u221a(g\u00b7L) - the dimensionless speed index that determines whether a hull is in displacement, semi-displacement or planing regime.

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