Fluids Package

Fluids Package Skill

Overview

The fluids library is a comprehensive Python package for mechanical and chemical engineers working with fluid flow problems. It provides validated correlations and functions for:

• Pipe flow and friction factor calculations
• Pump sizing and performance analysis
• Compressible and incompressible flow
• Heat exchanger design
• Two-phase flow
• Pressure drop calculations
• Fluid properties

The library implements over 100 correlations from the literature with extensive validation against published test cases.

Installation

pip install fluids

For full functionality including optimization routines:

pip install fluids[complete]

Key Modules

fluids.core

Core utilities and dimensional analysis functions.

fluids.friction

Friction factor calculations for pipe flow including:

• Darcy-Weisbach equation
• Colebrook-White correlation
• Moody diagram implementations
• Turbulent and laminar flow regimes

fluids.pump

Pump performance calculations:

• Affinity laws
• Specific speed
• NPSH calculations
• Pump curves and efficiency

fluids.compressible

Compressible flow calculations:

• Mach number relationships
• Choked flow conditions
• Isentropic flow
• Normal shock waves

fluids.fittings

Pressure drop through valves, fittings, and pipe components.

Common Functions with Engineering Context

Reynolds Number Calculation

The Reynolds number (Re) determines flow regime and is fundamental to all pipe flow calculations.

from fluids.core import Reynolds

# For pipe flow: Re = ρVD/μ
Re = Reynolds(V=2.5, D=0.05, rho=1000, mu=0.001)
# Result: 125000 (turbulent flow)

# Interpretation:
# Re  4000: Turbulent flow

Friction Factor (Darcy-Weisbach)

The friction factor (f) is used in the Darcy-Weisbach equation: ΔP = f(L/D)(ρV²/2)

from fluids.friction import friction_factor

# Colebrook-White correlation (implicit, most accurate)
f = friction_factor(Re=125000, eD=0.0001)  # eD = roughness/diameter
# Result: ~0.0178

# Moody correlation (explicit approximation)
from fluids.friction import friction_factor_Moody
f_moody = friction_factor_Moody(Re=125000, eD=0.0001)

# For laminar flow (Re  1.2: Supersonic

Compressible Flow - Choked Flow

Determine if flow is choked in a nozzle or orifice.

from fluids.compressible import P_critical_flow

# Gas properties
P_upstream = 500000  # Pa, upstream pressure
k = 1.4  # heat capacity ratio (air)

# Critical pressure for choked flow
P_crit = P_critical_flow(P=P_upstream, k=k)
# Result: ~264,000 Pa

# If downstream pressure  0 and 0 ≤ ε/D  0.3 but using incompressible equations
- **Solution**: Use compressible flow functions from fluids.compressible

## References

- Crane Technical Paper 410 (TP-410): "Flow of Fluids Through Valves, Fittings, and Pipe"
- Moody, L.F. (1944): "Friction factors for pipe flow"
- Colebrook, C.F. (1939): "Turbulent flow in pipes"
- Karassik's Pump Handbook (4th Edition)
- GPSA Engineering Data Book (14th Edition)

## Further Reading

- Official documentation: https://fluids.readthedocs.io/
- Source code: https://github.com/CalebBell/fluids
- Chemical Engineering Design Library: https://chemicals.readthedocs.io/

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [Soljourner](https://github.com/Soljourner)
- **Source:** [Soljourner/claude-engineering-skills](https://github.com/Soljourner/claude-engineering-skills)
- **License:** MIT

Install and usage instructions live in the source repository linked above.