Hull Froude Number Calculator

Froude Number Formula:

\[ Fr = \frac{v}{\sqrt{g \times L}} \]

Froude Number (dimensionless):

1. What is the Hull Froude Number?

Definition: The Froude number (Fr) is a dimensionless number that characterizes the resistance of a hull moving through water.

Purpose: It helps naval architects and marine engineers understand wave-making resistance and hull efficiency at different speeds.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ Fr = \frac{v}{\sqrt{g \times L}} \]

Where:

\( Fr \) — Froude number (dimensionless)
\( v \) — Velocity of the vessel (m/s)
\( g \) — Gravitational acceleration (9.8 m/s²)
\( L \) — Length of the hull at waterline (m)

Explanation: The Froude number compares the vessel's speed to the speed of wave propagation, indicating the wave-making resistance regime.

3. Importance of Froude Number

Details:

Fr < 0.4: Displacement mode (most ships)
0.4 < Fr < 1.0: Semi-displacement or semi-planing
Fr > 1.0: Planing hulls (high-speed craft)

4. Using the Calculator

Tips: Enter the vessel speed in m/s and hull length in meters. Both values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why is the Froude number important in ship design?
A: It helps predict wave-making resistance, which is a major component of total resistance at higher speeds.

Q2: What's a typical Froude number for commercial ships?
A: Most commercial vessels operate at Fr between 0.15 and 0.35 for fuel efficiency.

Q3: How does hull shape affect the Froude number significance?
A: Different hull forms have optimal speed ranges corresponding to specific Froude numbers.

Q4: Can I use knots for speed and feet for length?
A: The calculator uses m/s and m, but you can convert (1 knot = 0.5144 m/s, 1 ft = 0.3048 m).

Q5: What does a high Froude number indicate?
A: High Fr (>1) indicates planing conditions where dynamic lift becomes significant.