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Froude Number

Compare inertia against gravity to assess free-surface and gravity-wave dominance.

visual calculatorDimensionless Numbers

Read the flow shape before trusting the number.

This page turns a CFD setup into regime, scale, and dominant-effect cues. Adjust the calculator below and compare the moving graphic with the computed result.

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Froudefree surfacegravity wave
formula
KaTeX rendered
Fr = U / sqrt(g L)\begin{aligned}\text{Fr = U / sqrt(g L)}\end{aligned}
ASCII sourceFr = U / sqrt(g L)
Fr
0.9030
regime
subcritical

Fr below 1 indicates gravity waves can propagate upstream. Fr above 1 is typical of supercritical free-surface flow.