Reynolds number · roughness · inside diameter
Darcy friction factor
Inputs
Choose the relation the user has already determined is applicable; this workspace does not classify the flow regime.
User-entered dimensionless Reynolds number; viscosity, density, velocity, and regime are not derived.
Required only for the selected Swamee–Jain relation; use a compatible length unit with the stated inside diameter.
Required only for the selected Swamee–Jain relation; use the same length unit as roughness.
Results
Literal Darcy friction factor
0.020196
—Declared Reynolds number
100,000
—Literal declared relative roughness
0.00045
—fD = 0.25 / [log10(ε/(3.7D) + 5.74/Re^0.9)]²
A first-pass number, not a code check, certification, or approval. Read the method and its limits below. What this is and is not.
Nearby: Hydrostatic pressure · Flow continuity · Pipe mean velocity · Bernoulli equation
Method
Formula, when it applies, and when it does not
Apply a laminar relation or the explicit Swamee–Jain approximation to inputs and report a Darcy friction factor without classifying flow or solving a pipe system.
fD = 0.25 / [log10(ε/(3.7D) + 5.74/Re^0.9)]²
When
- User-declared calculation mode
- Swamee–Jain uses stated roughness and inside diameter
- Single scalar friction factor
Don’t
- The user declares the Swamee–Jain relation; this workspace does not classify flow regime or solve Colebrook iteratively. It does not calculate pressure drop, determine fluid properties, select pipe, pump, or fittings, solve a pipe network, establish capacity, safety, suitability, or approval.
Swamee & Jain (1976), Explicit equations for pipe-flow problems, ASCE