NeqSim can now turn a running ProcessSystem into first-pass release and gas dispersion screening cases, and then package those cases as formal CFD source-term handoffs. The workflow is intended for early safety studies, HAZOP follow-up, dynamic simulation reviews, and plant-data-backed screening where process stream pressure, temperature, flow, composition, and isolated inventory already exist in NeqSim.

The workflow is deliberately a screening bridge, not a replacement for CFD or regulatory QRA tools. Use it to identify credible leak cases, rank streams by consequence potential, generate source terms, create auditable scenario matrices, and prepare handoffs to detailed tools such as PHAST, FLACS, KFX, Safeti, or OpenFOAM.

Functional Review and Industrial Readiness

The current functionality is ready for structured screening studies and source-term handoff generation. It is not, by itself, a final industrial dispersion, layout, or QRA validation package. The generated CFD cases deliberately carry provenance, limitations, quality warnings, and notForFinalLayoutWithoutValidation = true so downstream tools and reviewers can see the engineering status of the case.

Capability Current status Industrial-use interpretation
Process integration Scans ProcessSystem streams and equipment outlet streams, then uses stream pressure, temperature, flow, and composition. Suitable for early safety screening from steady-state or dynamic NeqSim models. Validate that the scanned stream list matches the intended isolation envelope.
Source terms Uses LeakModel to produce time-series mass flow, temperature, pressure, vapor fraction, jet velocity, momentum, and droplet SMD. Suitable for first-pass release packages. Benchmark against project release-basis methods for final QRA or CFD.
Gas dispersion screening Uses Gaussian plume or dense-gas screening with flammable LFL and optional toxic endpoints. Suitable for ranking, weather sensitivity, and identifying cases needing detailed tools. Not a replacement for validated PHAST, FLACS, KFX, Safeti, OpenFOAM, or wind-tunnel/literature-backed studies.
Inventory basis Accepts either a representative volume or an evidence-linked TrappedInventoryCalculator.InventoryResult. Use trapped inventory for auditable studies. A manually entered volume is a screening assumption and is flagged in generated CFD cases.
Scenario taxonomy Generates configured leaks or the default 5 mm, 10 mm, 25 mm, 50 mm, full-bore, flange, instrument, and dropped-object cases. Useful as a complete screening matrix. Replace generic release frequencies with site- and equipment-specific leak-frequency data before QRA claims.
Weather envelope Generates D/F stability, low/high wind, winter/summer, and wind-sector cases. Useful for sensitivity screening. Replace or extend with site metocean data for industrial deliverables.
Consequence branching Carries immediate ignition, delayed ignition, jet fire, VCE, toxic-only, and no-ignition branch metadata. Useful for QRA handoff structure. Branch probabilities are screening defaults unless overwritten.
CFD handoff Writes neutral JSON, multi-case manifests, and an OpenFOAM-oriented source-term skeleton. Useful as a fast and traceable input package. Mesh, geometry, congestion, turbulence, species transport, boundaries, and ignition modelling remain study-specific.
Validation Focused tests cover schema/exporter behavior and broad reference envelopes for methane, CO2, propane, and H2S cases. Good regression protection. Final industrial use still needs project-specific validation against accepted tools, experiments, or published benchmark cases.

Before using results in an issued safety deliverable, confirm at least the following:

  1. The process state comes from a validated steady-state or dynamic NeqSim model.
  2. The isolated inventory is evidence-linked to P&IDs, line lists, equipment datasheets, or plant data.
  3. The release case set and leak frequencies match the applicable QRA basis.
  4. Weather cases are based on site metocean data and agreed stability assumptions.
  5. CFD source coordinates, direction, geometry, congestion, and ventilation are added by the CFD engineer.
  6. Screening endpoints are benchmarked against an accepted method for the project fluid and release class.
  7. The final report states assumptions, limitations, validation basis, and residual uncertainty.

Workflow

ReleaseDispersionScenarioGenerator scans a process flowsheet and performs five steps:

  1. Discover standalone streams and equipment outlet streams using the common stream introspection API.
  2. Skip streams with no flow or low pressure.
  3. Build a LeakModel source term for each remaining stream using the configured hole diameter, inventory volume, release duration, and boundary pressure.
  4. Run GasDispersionAnalyzer to calculate flammable LFL distances, dense-gas or Gaussian model selection, optional toxic endpoint distances, and compact JSON output.
  5. Optionally expand each stream into release taxonomy cases, batch weather cases, ignition/consequence branches, trapped-inventory provenance, and CFD source-term cases.

Java Example

The example below is mirrored by ReleaseDispersionScenarioGeneratorTest so the documented API calls are verified by the test suite.

import java.util.List;
import neqsim.process.equipment.separator.Separator;
import neqsim.process.equipment.stream.Stream;
import neqsim.process.equipment.valve.ThrottlingValve;
import neqsim.process.processmodel.ProcessSystem;
import neqsim.process.safety.BoundaryConditions;
import neqsim.process.safety.scenario.ReleaseDispersionScenarioGenerator;
import neqsim.process.safety.scenario.ReleaseDispersionScenarioGenerator.ReleaseDispersionScenario;
import neqsim.thermo.system.SystemInterface;
import neqsim.thermo.system.SystemSrkEos;

SystemInterface gas = new SystemSrkEos(298.15, 55.0);
gas.addComponent("methane", 0.90);
gas.addComponent("ethane", 0.10);
gas.setMixingRule("classic");

Stream feed = new Stream("feed gas", gas);
feed.setFlowRate(500.0, "kg/hr");
feed.setTemperature(25.0, "C");
feed.setPressure(55.0, "bara");

ThrottlingValve valve = new ThrottlingValve("inlet valve", feed);
valve.setOutletPressure(40.0, "bara");

Separator separator = new Separator("hp separator", valve.getOutletStream());

ProcessSystem process = new ProcessSystem();
process.add(feed);
process.add(valve);
process.add(separator);
process.run();

BoundaryConditions weather = BoundaryConditions.northSeaWinter();

ReleaseDispersionScenarioGenerator generator = new ReleaseDispersionScenarioGenerator(process)
    .boundaryConditions(weather)
    .holeDiameter(10.0, "mm")
    .inventoryVolume(5.0)
    .releaseDuration(60.0, 5.0);

List<ReleaseDispersionScenario> scenarios = generator.generateScenarios();
ReleaseDispersionScenario firstScenario = scenarios.get(0);

double peakReleaseRate = firstScenario.getSourceTerm().getPeakMassFlowRate();
double distanceToLfl = firstScenario.getDispersionResult().getDistanceToLflM();
String scenarioJson = firstScenario.toJson();

Configuration

Method Purpose
boundaryConditions(BoundaryConditions) Sets wind, stability, ambient pressure, ambient temperature, and terrain basis.
holeDiameter(double, String) Sets the representative leak hole size in m, mm, or in.
fullBoreDiameter(double, String) Sets the full-bore rupture diameter used by taxonomy cases.
inventoryVolume(double) Sets the isolated inventory volume used by the source-term blowdown model.
trappedInventory(InventoryResult) Uses a TrappedInventoryCalculator result as the volume and inventory provenance basis.
releaseDuration(double, double) Sets source-term duration and time step in seconds.
minimumPressure(double) Skips streams below the specified absolute pressure in bara.
minimumMassFlowRate(double) Skips streams below the specified mass flow rate in kg/s.
releaseHeight(double) Sets the effective release height used in dispersion calculations.
toxicEndpoint(String, double) Adds a toxic concentration endpoint in ppm for a component in the fluid.
useDefaultScenarioTaxonomy() Generates 5 mm, 10 mm, 25 mm, 50 mm, full-bore, flange, instrument, and dropped-object cases.
useDefaultWeatherEnvelope() Generates winter/summer, low/high wind, D/F stability, and wind-sector cases.
consequenceBranches(List<ConsequenceBranch>) Adds immediate ignition, delayed ignition, jet fire, VCE, toxic-only, and no-ignition branch metadata.
generateCfdSourceTermCases() Converts generated scenarios to validated CFD source-term schema objects.

Industrial Scenario Matrix

The generator can expand each eligible stream into an industrial screening matrix. This is useful when the process model is already connected to plant data or dynamic simulations and the safety engineer wants consistent leak cases across the plant.

import java.util.List;
import neqsim.process.safety.cfd.CfdSourceTermCase;
import neqsim.process.safety.inventory.TrappedInventoryCalculator;
import neqsim.process.safety.inventory.TrappedInventoryCalculator.InventoryResult;
import neqsim.process.safety.scenario.ReleaseDispersionScenarioGenerator;

InventoryResult inventory = new TrappedInventoryCalculator()
   .setFluid(gas)
   .setOperatingConditions(55.0, "bara", 25.0, "C")
   .addEquipmentVolume("V-101", 4.0, 0.0, null)
   .calculate();

List<CfdSourceTermCase> cfdCases = new ReleaseDispersionScenarioGenerator(process)
   .trappedInventory(inventory)
   .fullBoreDiameter(150.0, "mm")
   .useDefaultScenarioTaxonomy()
   .useDefaultWeatherEnvelope()
   .releaseDuration(300.0, 5.0)
   .toxicEndpoint("H2S", 100.0)
   .generateCfdSourceTermCases();

The default taxonomy includes:

Case Purpose
5 mm, 10 mm, 25 mm, 50 mm leaks Standard process leak size screening.
Full-bore rupture Uses the configured full-bore diameter.
Flange leak Representative gasket or bolted-joint failure.
Instrument leak Small-bore instrument connection failure.
Dropped-object damage Large leak caused by impact.

Release frequency values in these cases are generic placeholders for screening and must be replaced by site-specific leak-frequency data before QRA risk claims are made.

Trapped Inventory Basis

Use TrappedInventoryCalculator when volume should come from evidence-linked equipment and pipe segments rather than a single representative number. The resulting CFD case records the inventory basis, gas-filled volume, liquid-filled volume, density, mass, per-segment records, and warnings such as missing document evidence.

InventoryResult inventory = new TrappedInventoryCalculator()
   .setFluid(gas)
   .setOperatingConditions(55.0, "bara", 25.0, "C")
   .addEquipmentVolume("V-101", 4.0, 0.0, null)
   .addPipeSegment("export-line-isolated-section", 0.203, 120.0, 0.0, null)
   .calculate();

If inventoryVolume(double) is used instead, generated CFD cases include a warning that the volume is a screening assumption.

The trapped-inventory result is applied to all generated cases from the configured generator. For multi-area plants, create one generator per isolation envelope or provide area-specific inventory results so each release case carries the correct blocked-in volume and evidence basis.

CFD Source-Term Handoff

CfdSourceTermCase is a neutral, versioned JSON schema for passing NeqSim source terms to detailed CFD studies. It is deliberately not OpenFOAM-specific. Each case contains:

Use validate() before handing a case to another tool:

CfdSourceTermCase cfdCase = cfdCases.get(0);
CfdSourceTermCase.ValidationResult validation = cfdCase.validate();
if (!validation.isValid()) {
   throw new IllegalStateException(validation.toJson());
}

CfdSourceTermExporter writes neutral JSON, a multi-case manifest, and an OpenFOAM-oriented source-term skeleton:

import neqsim.process.safety.cfd.CfdSourceTermExporter;

CfdSourceTermExporter exporter = new CfdSourceTermExporter();
exporter.exportJson(cfdCase, "case.json");
exporter.exportManifest(cfdCases, "manifest.json");
exporter.exportOpenFoamSkeleton(cfdCase, "openfoam-source-term");

The OpenFOAM skeleton contains case.json, constant/releaseSourceProperties, and tabulated constant/sourceTimeSeries files for mass flow, temperature, and jet momentum. It still requires study-specific mesh, geometry, turbulence model, species transport setup, boundary conditions, and ignition logic.

The built-in validate() method checks required schema sections and key positive source-term fields. It is a handoff-schema check, not a physics validation. A valid schema can still represent a screening case with uncertain inventory, generic release frequency, or missing site coordinates; those assumptions appear in qualityWarnings and provenance.limitations.

Result Data

Each generated ReleaseDispersionScenario contains:

The toJson() method provides a compact representation suitable for notebooks, MCP tools, screening reports, and external consequence-analysis handoffs.

For CFD handoff, prefer ReleaseDispersionScenario.toCfdSourceTermCase() or ReleaseDispersionScenarioGenerator.generateCfdSourceTermCases() because those APIs preserve schema version, provenance, assumptions, and validation metadata.

Sour Gas Endpoint

For sour gas streams, configure a toxic endpoint in addition to flammable endpoints:

List<ReleaseDispersionScenario> sourScenarios = new ReleaseDispersionScenarioGenerator(process)
    .boundaryConditions(BoundaryConditions.northSeaWinter())
    .holeDiameter(8.0, "mm")
    .inventoryVolume(2.0)
    .releaseDuration(60.0, 5.0)
    .toxicEndpoint("H2S", 100.0)
    .generateScenarios();

The toxic endpoint uses the same released gas composition as the flammable screening case. If the named component is not present, the toxic distance is reported as not reached.

Engineering Use

This workflow is useful for:

The focused validation suite includes reference-envelope cases for methane jet dispersion, CO2 dense-gas toxic endpoints, propane heavy-gas flammable endpoints, and H2S toxic plumes. These tests verify the screening model behavior stays within broad benchmark envelopes; they do not replace project-specific validation against PHAST, FLACS, KFX, Safeti, OpenFOAM, or wind-tunnel/literature data for final design.

Recommended next validation steps for industrial qualification are:

For final layout, escalation, or regulatory studies, validate screening results with a detailed consequence-analysis method and site-specific assumptions.