Pipeline Modeling Documentation

Documentation Index

This documentation covers pipeline pressure drop, flow, and heat transfer calculations in NeqSim.

Overview & Getting Started

Document	Description
Pipeline Pressure Drop	Overview of all pipeline models, quick start examples
Model Recommendations	Which model to use for your application

Detailed Model Documentation

Document	Description
Beggs & Brill Correlation	Multiphase flow correlation theory and usage
Friction Factor Models	Haaland, Colebrook-White, laminar/turbulent
Heat Transfer	Non-adiabatic operation, cooling, Gnielinski
Transient Simulation	Dynamic simulation, slow wave propagation
Water Hammer	Fast transients, pressure surges, MOC solver

Quick Model Selection

┌─────────────────────────────────────────────────────────────────┐
│                        PIPELINE MODELS                          │
├─────────────────────────────────────────────────────────────────┤
│                                                                 │
│  Single-Phase Gas         →  AdiabaticPipe                     │
│  Single-Phase Liquid      →  PipeBeggsAndBrills                │
│  Two-Phase (Gas-Liquid)   →  PipeBeggsAndBrills                │
│  Three-Phase (G-O-W)      →  PipeBeggsAndBrills                │
│  With Elevation           →  PipeBeggsAndBrills                │
│  With Heat Transfer       →  PipeBeggsAndBrills                │
│  Slow Transient/Dynamic   →  PipeBeggsAndBrills                │
│  Water Hammer/Fast Trans. →  WaterHammerPipe                   │
│  Quick Estimate           →  AdiabaticTwoPhasePipe             │
│                                                                 │
└─────────────────────────────────────────────────────────────────┘

Key Classes

Class	Package	Description
PipeBeggsAndBrills	neqsim.process.equipment.pipeline	Multiphase, elevation, heat transfer, slow transient
WaterHammerPipe	neqsim.process.equipment.pipeline	Water hammer, fast pressure transients (MOC)
AdiabaticPipe	neqsim.process.equipment.pipeline	Single-phase compressible gas
AdiabaticTwoPhasePipe	neqsim.process.equipment.pipeline	Two-phase, horizontal
TwoFluidPipe	neqsim.process.equipment.pipeline	Two-fluid model with drift-flux
TransientPipe	neqsim.process.equipment.pipeline	Transient drift-flux with AUSM+ scheme
TwoPhasePipeFlowSystem	neqsim.fluidmechanics.flowsystem	Low-level non-equilibrium mass/heat transfer

Low-Level Fluid Mechanics

For detailed non-equilibrium mass and heat transfer calculations, the TwoPhasePipeFlowSystem in the fluidmechanics package provides:

• Multicomponent mass transfer using Krishna-Standart film model
• Flow pattern detection (Taitel-Dukler, Baker, Barnea, Beggs-Brill)
• Interfacial area calculations for all flow patterns
• Wall heat transfer with multiple boundary conditions
• Bidirectional mass transfer (evaporation and dissolution)

See Fluid Mechanics README and Two-Phase Pipe Flow Model for details.

Common Parameters

Geometry

• setLength(double meters) - Pipe length
• setDiameter(double meters) - Inside diameter
• setElevation(double meters) - Elevation change (+ = uphill)
• setPipeWallRoughness(double meters) - Surface roughness

Numerical

• setNumberOfIncrements(int n) - Number of calculation segments

Calculation Mode

• setOutletPressure(double bara) - Specify outlet pressure, calculate flow rate
• Default mode: Specify flow rate, calculate outlet pressure

Heat Transfer

• setRunAdiabatic(boolean) - Enable/disable heat exchange
• setConstantSurfaceTemperature(double K) - Ambient temperature
• setHeatTransferCoefficient(double W_m2K) - Overall U-value

Transient

• setCalculateSteadyState(boolean) - Switch steady/transient mode
• runTransient(double dt, UUID id) - Run one time step

Typical Roughness Values

Pipe Material	Roughness (mm)	Roughness (m)
New steel	0.046	4.6×10⁻⁵
Corroded steel	0.15-0.3	1.5-3×10⁻⁴
Stainless	0.015	1.5×10⁻⁵
Plastic/GRP	0.005	5×10⁻⁶

Validation Summary

Test Case	Model	Deviation
Gas (Darcy-Weisbach)	All models	<1%
Liquid turbulent	Beggs-Brill	-1.4%
Liquid laminar	Beggs-Brill	0%
Uphill two-phase	Beggs-Brill	Validated
Transient convergence	Beggs-Brill	<15%

Version History

• December 2025: Fixed Java 8 compatibility in TwoPhasePipeFlowSystem tests
• December 2025: Added bidirectional mass transfer mode
• December 2025: Improved solver stability for edge cases
• 2025: Added calculate flow from outlet pressure mode
• 2025: Fixed AdiabaticPipe and AdiabaticTwoPhasePipe calcFlow() methods
• 2024: Added transient with friction and hydrostatic
• 2024: Fixed Haaland exponent (^1.11)
• 2024: Fixed single-phase liquid handling
• 2024: Added Gnielinski heat transfer
• 2024: Added flow regime detection

Support

For questions or issues:

• GitHub Issues: https://github.com/equinor/neqsim/issues
• Documentation: https://equinor.github.io/neqsim/