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Froude Number Calculator
Calculate the Froude number for open-channel flow using the section-mean speed and hydraulic depth, defined as flow area divided by free-surface top width. Choose input units and calculate one value within the stated conditions.
Inputs
Calculations run in this browser. Scientific notation such as 1.2e-3 is supported. Do not group thousands.
Result
Froude number Fr
Enter values and select Calculate.
Fr = V / √(gD), D = A/T
Assumptions
Required: section-mean open-channel flow with approximately hydrostatic pressure. Use hydraulic depth D = A/T, with free-surface top width T. Excluded: substituting hydraulic radius A/wetted perimeter or predicting flooding and jump location from Fr alone.
Displayed values are floating-point approximations. Design safety factors and unprovided error contributions are not calculated.
Formula references and credits
NaNa Lab created the code, descriptions, icons and preview images. Text, figures and code from the linked references have not been reproduced.
Physical constants: NIST / CODATA 2022. The values of μ₀ and ε₀ are measured recommendations, not exact defining constants. Values and precision notes are in the source record.
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