Friction Factor Calculator
Calculate Darcy friction factor using Moody's approximation for pipe flow analysis
Friction Factor Calculator
Commercial steel, new - Roughness: 0.045 mm
For circular pipes: D = diameter
Absolute roughness height
Re = ρVD/μ (dimensionless)
Must be less than 0.01 for Moody equation
Friction Factor Results
Moody Equation: f = 0.0055 × (1 + (2×10⁴ × k/D + 10⁶/Re)^(1/3))
Valid Range: 4,000 ≤ Re ≤ 5×10⁸, k/D < 0.01
Pipe Diameter: 0.000 m
Surface Roughness: 0.000 mm
Example Calculation
Commercial Steel Pipe
Hydraulic Diameter: 2 m
Surface Roughness: 0.01 m (quite rough for demonstration)
Reynolds Number: 4,500 (turbulent flow)
Calculation Steps
1. k/D = 0.01/2 = 0.005
2. Check validity: 4,500 > 4,000 ✓, k/D < 0.01 ✓
3. f = 0.0055 × (1 + (2×10⁴×0.005 + 10⁶/4500)^(1/3))
4. f = 0.0055 × (1 + (100 + 222.2)^(1/3))
5. f = 0.0055 × (1 + 6.85) = 0.0432
Common Pipe Roughness
Flow Regime Guide
Laminar Flow
Re < 2,300
f = 64/Re
Transitional Flow
2,300 ≤ Re < 4,000
Interpolated values
Turbulent Flow
Re ≥ 4,000
Moody equation valid
Calculation Tips
Moody equation valid for Re: 4,000 to 5×10⁸
Relative roughness k/D must be < 0.01
Higher roughness increases friction factor
Use hydraulic diameter for non-circular pipes
Understanding Friction Factor
What is Friction Factor?
The friction factor (f) is a dimensionless number used in the Darcy-Weisbach equation to calculate pressure losses due to friction in pipe flow. It depends on the Reynolds number, relative roughness, and flow regime. The friction factor is essential for designing piping systems and calculating pump requirements.
Moody's Approximation
The Moody equation provides an explicit approximation to the implicit Colebrook equation. It's valid for turbulent flow in commercial pipes and is widely used in engineering practice. The equation accounts for both the Reynolds number effect and the relative roughness effect.
Applications
- •Pressure drop calculations in piping systems
- •Pump sizing and selection
- •Energy loss analysis in fluid systems
- •HVAC system design
- •Water distribution network analysis
Factors Affecting Friction
- •Reynolds number (flow velocity, fluid properties)
- •Relative roughness (surface condition)
- •Pipe geometry and fittings
Key Equations
Moody Equation (Turbulent)
f = 0.0055 × (1 + (2×10⁴×k/D + 10⁶/Re)^(1/3))
Valid for 4,000 ≤ Re ≤ 5×10⁸, k/D < 0.01
Laminar Flow
f = 64 / Re
Valid for Re < 2,300
Reynolds Number
Re = ρ × V × D / μ
ρ: density, V: velocity, D: diameter, μ: viscosity
Darcy-Weisbach Equation
Δp = f × (L/D) × (ρ×V²)/2
L: pipe length, Δp: pressure drop