neqsim-two-phase-flow-regime-screening

name	neqsim-two-phase-flow-regime-screening
calculation_basis	screening
version	0.1.0
description	Educational two-phase flow-regime screening that classifies a horizontal gas-liquid flow pattern from superficial velocities using a simplified public Mandhane-style map and flags slug risk. USE WHEN: a task needs a public, screening-level flow-regime flag (stratified, slug, annular, bubble) and slug-risk triage to pair with slug-flow and flow-induced-vibration work.
last_verified	2026-06-18
requires	{"python_packages":[],"java_packages":[],"env":[],"network":[]}

Two-Phase Flow Regime Screening

Use this skill for public, educational two-phase flow-regime screening. It classifies a horizontal gas-liquid flow pattern from the superficial gas and liquid velocities using a simplified Mandhane-style decision tree and flags slug risk so an agent can decide whether to invoke validated NeqSim multiphase pipe-flow modelling.

When to Use

• When a user asks what flow regime a horizontal line is likely in.
• When an agent needs a quick slug-risk flag before slug or vibration work.
• When examples must run without confidential pipeline models or field data.

Inputs

Provide either the superficial velocities directly, or enough data to compute them:

• superficial_gas_velocity: gas superficial velocity Vsg in m/s.
• superficial_liquid_velocity: liquid superficial velocity Vsl in m/s.

or

• pipe_inner_diameter: pipe inner diameter in m.
• gas_mass_flow: gas mass flow in kg/s.
• liquid_mass_flow: liquid mass flow in kg/s.
• gas_density: gas density in kg/m3.
• liquid_density: liquid density in kg/m3.

Outputs

• superficial_gas_velocity_m_s: gas superficial velocity used.
• superficial_liquid_velocity_m_s: liquid superficial velocity used.
• mixture_velocity_m_s: Vsg + Vsl.
• flow_regime: stratified-smooth, stratified-wavy, elongated-bubble, slug, dispersed-bubble, or annular-mist.
• slug_risk: true when the regime is slug or elongated-bubble.
• regime_warning: ok, slug-risk, or high-velocity.
• assumptions: public assumptions used by the placeholder model.

Engineering Method

The Python class TwoPhaseRegimeModel uses a simplified public Mandhane-style classifier for horizontal flow:

• superficial velocities use Vs = (mdot / rho) / (pi/4 * D^2) when computed from flows.
• the regime is selected from public approximate boundaries: annular-mist above Vsg = 10 m/s, dispersed-bubble above Vsl = 2 m/s, stratified below Vsl = 0.1 m/s, elongated-bubble for low gas velocity, otherwise slug.
• slug_risk is flagged for the slug and elongated-bubble regimes.

This is educational and screening-only logic. The boundaries are public approximations, not the digitized Mandhane chart or a mechanistic model. It ignores pipe inclination, surface tension, viscosity, entrainment, and transient slugging. It is not a replacement for validated multiphase flow modelling and qualified flow assurance review.

Python Usage Pattern

from two_phase_flow_regime_screening import TwoPhaseRegimeModel

model = TwoPhaseRegimeModel()
result = model.evaluate(
    superficial_gas_velocity=3.0,
    superficial_liquid_velocity=0.5,
)

print(result.flow_regime)
print(result.slug_risk)
print(result.regime_warning)

Related NeqSim Functionality

For validated multiphase flow behaviour, redirect to existing NeqSim classes:

• neqsim.process.equipment.pipeline.PipeBeggsAndBrills — Beggs and Brills multiphase pressure drop and holdup with internal regime determination.
• neqsim.process.equipment.pipeline.TwoFluidPipe — two-fluid transient pipe flow.
• neqsim.process.equipment.pipeline.AdiabaticTwoPhasePipe — adiabatic two-phase line modelling.

This skill is a public flow-regime triage layer that decides when to invoke those validated pipe-flow classes.

When the regime is transient rather than steady — terrain slugging, ramp-up surge, shut-in and restart — escalate instead to the neqsim-olga-multiphase-simulator skill (or the olga-simulation-agent), which runs an OLGA transient case and reads its trend and profile results.

Validation Checklist

• Either superficial velocities or full flow/density/diameter data are supplied.
• Velocities are non-negative and finite.
• The regime and slug-risk flag are reported as screening indicators.
• Tests cover stratified, slug, annular, computed velocities, and invalid input.
• Real regime analysis is redirected to validated NeqSim pipe-flow classes and qualified review.

Common Mistakes

Symptom	Cause	Fix
Regime looks wrong	Used vertical or inclined line	This map is for horizontal flow only
Velocities too high	Mass flow given in kg/h not kg/s	Use kg/s, or pass velocities directly
Slug missed	Operating near a public boundary	Use a mechanistic NeqSim model near boundaries

Limitations

• Horizontal flow only; no inclination or terrain slugging.
• Public approximate boundaries, not the digitized Mandhane chart.
• No surface-tension, viscosity, or entrainment effects.

References

• NeqSim repository: https://github.com/equinor/neqsim
• NeqSim Skills Guide: https://github.com/equinor/neqsim/blob/master/docs/integration/skills_guide.md