Calculateur de Nombre de Froude Gratuit
Calculez le nombre de Froude d'un écoulement à surface libre. Déterminez si l'écoulement est fluvial ou torrentiel.
Froude Number
0.957990
Froude Number vs Flow Velocity
Formule
Froude Number
The Froude number characterises the ratio of flow inertia to gravitational effects in open-channel flow.
Formula
Fr = v / sqrt(g d)
Fr < 1: subcritical (tranquil). Fr = 1: critical. Fr > 1: supercritical (rapid).
Exemple Résolu
River at 3 m/s with 1 m depth.
- 01Fr = v / sqrt(g d)
- 02Fr = 3 / sqrt(9.807 * 1)
- 03Fr = 3 / 3.131
- 04Fr = 0.958 (subcritical, but nearly critical)
Questions Fréquentes
What is the physical meaning of the Froude number?
It compares the speed of the flow to the speed of surface gravity waves. When Fr > 1, flow moves faster than waves can propagate upstream, so upstream conditions cannot influence downstream.
How does the Froude number relate to ship design?
For ships, the Froude number (based on hull length) determines wave-making resistance. Ships are most efficient below the hull speed, roughly Fr = 0.4.
What happens at Fr = 1?
Critical flow, with minimum specific energy for a given discharge. This condition is used in weir design to measure flow rates.
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