Summary

This PR introduces a new Hardy Cross looped pipeline network solver for handling ring mains, parallel pipelines, and complex gathering systems. It also includes a comprehensive update to the Oil & Gas Design Operations Review document with improved documentation of existing functionality.

New Features

1. Hardy Cross Looped Pipeline Network Solver

A complete implementation of the classic Hardy Cross iterative method for solving looped pipe networks.

New Classes

Key Features

• Automatic Loop Detection: Uses graph theory (DFS spanning tree) to find all independent loops
• Hardy Cross Iteration: Classic iterative solver for balancing pressure drops
• Multiple Node Types: Source, sink, and junction nodes
• Solver Types: HARDY_CROSS, SEQUENTIAL, NEWTON_RAPHSON (future)
• JSON Export: Integration-ready output format
• Configurable Parameters: Tolerance, max iterations, relaxation factor

Algorithm

The Hardy Cross method calculates flow corrections for each loop:

$$\Delta Q = -\frac{\sum_i H_i}{2 \sum_i \left|\frac{H_i}{Q_i}\right|}$$

Where:

• $H_i$ = head loss in pipe $i$
• $Q_i$ = flow rate in pipe $i$

Usage Example

LoopedPipeNetwork network = new LoopedPipeNetwork("Distribution Ring");
network.setFluidTemplate(gas);

// Add nodes
network.addSourceNode("supply", 50.0, 2000.0);  // 50 bar, 2000 kg/hr
network.addJunctionNode("A");
network.addJunctionNode("B");
network.addSinkNode("customer", 2000.0);

// Add pipes forming a ring
network.addPipe("supply", "A", "inlet", 1000.0, 0.3);
network.addPipe("A", "B", "ring1", 500.0, 0.2);
network.addPipe("B", "supply", "ring2", 500.0, 0.2);  // Creates loop
network.addPipe("A", "customer", "outlet", 200.0, 0.15);

network.run();  // Solves using Hardy Cross

Applications

• Gas distribution networks with ring mains
• Offshore pipeline networks with redundant paths
• Water/steam distribution systems
• Any pipe network with multiple flow paths

2. Example Notebook

Notebook Contents:

• Triangle loop detection
• Distribution ring main
• Offshore subsea ring network
• Figure-8 network (two loops)
• NetworkLoop API demonstration
• JSON output for integration

Documentation Updates

3. Oil & Gas Design Operations Review

Major update to NEQSIM_OIL_GAS_DESIGN_OPERATIONS_REVIEW.md:

Updated Sections

New Documentation of Existing Features

Well Performance (IPR) - WellFlow.java:

• Production Index model
• Vogel correlation for oil wells
• Fetkovich correlation for gas wells
• Backpressure equation with non-Darcy term
• Table-driven IPR from well tests
• Multi-layer commingled wells

Reservoir Coupling - ReservoirCouplingExporter.java:

• VFP table generation (VFPPROD/VFPINJ)
• Eclipse 100/E300/Intersect formats
• Separator efficiency curves
• Compression curves
• Network deliverability constraints

Erosion-Corrosion - ManifoldMechanicalDesignCalculator.java:

• API RP 14E erosional velocity: Ve = C/√ρ
• Configurable C-factor (100-150)
• Gas, liquid, multiphase velocity limits

Compressor Drivers:

• GasTurbineDriver: Ambient derating, part-load efficiency, fuel consumption
• ElectricMotorDriver: VFD speed control, efficiency curves
• SteamTurbineDriver: Extraction/condensing modes

Condition Monitoring:

• FlowInducedVibrationAnalyser: LOF/FRMS methods
• ConditionBasedReliability: Health index, RUL estimation
• DegradationModel: Linear, Exponential, Weibull, ML-based

Flare System - FlareStack.java:

• Radiation models: Point Source, Chamberlain line-source
• Emissions tracking: CO₂, H₂O, NOx, SO₂, THC, CO
• Tip backpressure calculation
• Air/steam assist modeling

4. Reference Manual Index Update

Updated REFERENCE_MANUAL_INDEX.md:

5. Pipeline Network Enhancement Proposal

Updated PIPELINE_NETWORK_SOLVER_ENHANCEMENT.md:

• Added "Implementation Status: ✅ COMPLETE" header
• Listed implemented classes with links
• Added key features summary

Test Results

All 12 unit tests pass:

Tests run: 12, Failures: 0, Errors: 0, Skipped: 0

Test Coverage:

• testTriangleLoopDetection - Basic loop detection
• testTwoLoopDetection - Multiple independent loops
• testTreeNetworkNoLoops - Tree topology (no loops)
• testRingMainNetworkCreation - Ring main topology
• testHardyCrossConvergence - Solver convergence
• testNetworkLoopClass - Loop member management
• testSolutionSummary - Output format
• testJsonOutput - JSON serialization
• testParallelPipes - Parallel pipe loop detection
• testSolverTypeSelection - Solver configuration
• testRelaxationFactor - Parameter setting
• testOffshoreRingNetwork - Realistic offshore topology

Files Changed

New Files (5)

src/main/java/neqsim/process/equipment/network/
├── NetworkLoop.java
├── LoopDetector.java
└── LoopedPipeNetwork.java

src/test/java/neqsim/process/equipment/network/
└── LoopedPipeNetworkTest.java

docs/examples/
└── LoopedPipelineNetworkExample.ipynb

Modified Files (3)

docs/
├── NEQSIM_OIL_GAS_DESIGN_OPERATIONS_REVIEW.md
├── REFERENCE_MANUAL_INDEX.md
└── process/PIPELINE_NETWORK_SOLVER_ENHANCEMENT.md

Breaking Changes

None. This PR adds new functionality without modifying existing APIs.

Migration Guide

No migration required. Existing code continues to work unchanged.

Future Work

1. Newton-Raphson Solver: Implement simultaneous solution for large networks
2. Transient Looped Networks: Extend TwoFluidPipe for looped transient simulation
3. OPC-UA Connector: Real-time data integration
4. MEG/TEG Tracking: System-wide inhibitor tracking

Related Issues

• Enhancement request for looped network solver
• Documentation review for O&G design capabilities

Reviewers

Please review:

1. Loop detection algorithm correctness
2. Hardy Cross convergence behavior
3. Documentation accuracy for existing features
4. Example notebook clarity

Checklist

• Code compiles without errors
• All unit tests pass
• JavaDoc added to new classes
• Example notebook created
• Documentation updated
• Reference manual index updated
• No breaking changes to existing APIs