อัปเดต 2026-09-07

Moody / friction-factor explorer

Colebrook–White vs Swamee–Jain

Teaching calculator that resolves the Darcy friction factor from Reynolds number and relative roughness, showing the laminar, transitional, and turbulent regimes and comparing the implicit Colebrook–White solution against the explicit Swamee–Jain approximation.

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Laminar (Re<2300): Hagen–Poiseuille f=64/Re, roughness-independent. Turbulent (Re>4000): Colebrook–White solved by fixed-point iteration on g=1/√f seeded from Swamee–Jain (converges in 3–4 steps), or the explicit Swamee–Jain formula directly. The 2300–4000 transitional band has no universal correlation and is flagged uncertain rather than interpolated.

สมการ

Laminar (Hagen–Poiseuille)

f = \frac{64}{R e}

Re < 2300; roughness-independent

Colebrook–White (1939, implicit)

\frac{1}{f} = - 2 lo g_{10} (\frac{ε / D}{3.7} + \frac{2.51}{R e f})

solved by fixed-point iteration on g=1/√f; the primary turbulent correlation (Re>4000)

Swamee–Jain (1976, explicit)

f = \frac{0.25}{[ lo g _{10} ( \frac{ε / D}{3.7} + \frac{5.74}{R e ^{0.9}} ) ] ^{2}}

within ≈1% of Colebrook over Re∈[4×10³,1×10⁸], ε/D∈[1×10⁻⁶,1×10⁻²]

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