Froude number formula |
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\( Fr \;=\; \dfrac{ v }{ \sqrt{ g \cdot h_m } } \) (Froude Number) \( v \;=\; Fr \cdot \sqrt{ g \cdot h_m } \) \( g \;=\; \dfrac{ v^2 }{ h_m \cdot Fr^2 }\) \( h_m \;=\; \dfrac{ v^2 }{ g \cdot Fr^2} \) |
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| Symbol | English | Metric |
| \( Fr \) = Froude Number | \(dimensionless\) | \( dimensionless \) |
| \( v \) = Flow Velocity | \(ft\;/\;sec\) | \(m\;/\;s\) |
| \( g \) = Gravitational Acceleration | \(ft\;/\;sec^2\) | \(m\;/\;s^2\) |
| \( h_m \) = Mean Depth | \(ft\) | \(m\) |
Froude number, abbreviated as Fr, a dimensionless number, is the ratio of inertial force to gravitational forces acting on a fluid flow. It is used for wave and surface behavior for mixed natural and forced convection. It is used used in fluid dynamics to characterize the flow regime and behavior of fluids, particularly in open channel flow or flow around objects. The Froude number is important in various applications, such as open channel hydraulics, river engineering, and ship hydrodynamics. It helps in understanding the behavior of flow, determining flow patterns, and predicting the occurrence of hydraulic phenomena.
Froude Number Interpretation
- Low Froude Number (Fr << 1) - Subcritical Flow, the flow is slow, and gravitational forces dominate (calm river flow).
- Froude Number (Fr ≈ 1) - Critical Flow, a transitional state where inertial and gravitational forces are balanced.
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High Froude Number (Fr >> 1) - Supercritical Flow, the flow is fast, and inertial forces dominate (rapids or shallow fast-moving water).
