Flow Resistance Converter Nf Calculator
Free Flow resistance n↔f Calculator for hydrology & water resources. Enter variables to compute results with formulas and detailed steps.
Formula
f = 8g x n^2 / R^(1/3)
The Darcy-Weisbach friction factor f relates to Manning n through: f = 8g x n^2 / R^(1/3), where g = 9.81 m/s2 and R is the hydraulic radius (m). The Chezy coefficient C = R^(1/6) / n = sqrt(8g/f). Manning velocity V = (1/n) x R^(2/3) x S^(1/2). Darcy-Weisbach velocity V = sqrt(8gRS/f).
Worked Examples
Example 1: Concrete-Lined Channel
Problem: Manning n = 0.013, hydraulic radius = 0.8 m, slope = 0.002.
Solution: Darcy-Weisbach f = 8 x 9.81 x 0.013^2 / 0.8^(1/3) = 0.01426\nChezy C = 0.8^(1/6) / 0.013 = 74.3\nVelocity = (1/0.013) x 0.8^(2/3) x 0.002^(1/2) = 2.96 m/s\nFroude = 2.96 / sqrt(9.81 x 0.8) = 1.06 (supercritical)
Result: f = 0.0143 | C = 74.3 | V = 2.96 m/s | Supercritical
Example 2: Natural Gravel Stream
Problem: Manning n = 0.035, hydraulic radius = 1.2 m, slope = 0.005.
Solution: Darcy-Weisbach f = 8 x 9.81 x 0.035^2 / 1.2^(1/3) = 0.0901\nChezy C = 1.2^(1/6) / 0.035 = 29.5\nVelocity = (1/0.035) x 1.2^(2/3) x 0.005^(1/2) = 1.83 m/s\nFroude = 1.83 / sqrt(9.81 x 1.2) = 0.53 (subcritical)
Result: f = 0.0901 | C = 29.5 | V = 1.83 m/s | Subcritical
Frequently Asked Questions
How accurate are the results from Flow Resistance Converter Nf Calculator?
All calculations use established mathematical formulas and are performed with high-precision arithmetic. Results are accurate to the precision shown. For critical decisions in finance, medicine, or engineering, always verify results with a qualified professional.
What formula does Flow Resistance Converter Nf Calculator use?
The formula used is described in the Formula section on this page. It is based on widely accepted standards in the relevant field. If you need a specific reference or citation, the References section provides links to authoritative sources.
How do I get the most accurate result?
Enter values as precisely as possible using the correct units for each field. Check that you have selected the right unit (e.g. kilograms vs pounds, meters vs feet) before calculating. Rounding inputs early can reduce output precision.
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