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.
Froude number
0.171 -
Regime
Displacement
Formula, assumptions, and limits
Typical VLCC Fn ≈ 0.15, bulker 0.17, feeder container 0.22, ro-ro 0.26. Fn > 0.3 wave-making resistance dominates; design hull shape changes dramatically.
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| Speed through water | m/s | log | |
| Waterline length | m | hydrostatic table |