OrcaFlex Operability Analysis Skill

Assess system operability across multiple sea states with envelope generation, critical heading analysis, and weather downtime calculations.

Version Metadata

version: 1.0.0
python_min_version: '3.10'
dependencies:
  orcaflex-modeling: '>=2.0.0,<3.0.0'
  orcaflex-post-processing: '>=1.0.0,<2.0.0'
orcaflex_version: '>=11.0'
compatibility:
  tested_python:
  - '3.10'
  - '3.11'
  - '3.12'
  - '3.13'
  os:
  - Windows
  - Linux
  - macOS

Changelog

[1.0.0] - 2026-01-17

Added:

Initial release with operability envelope generation
Weather downtime calculations from wave scatter
Critical heading analysis
Interactive Plotly visualization

When to Use

Operability envelope generation for mooring systems
Weather downtime calculations from scatter diagrams
Critical heading identification for design loads
Multi-sea-state analysis (1yr, 10yr, 100yr return periods)
Tension limit assessment (intact vs damaged conditions)
Annual operational availability studies
Polar coordinate visualization of system limits

Prerequisites

OrcaFlex simulation results (.sim files) for multiple headings
Wave scatter diagram (Hs-Tp probability matrix)
Python environment with digitalmodel package installed
Tension limits for intact and damaged conditions

Operability Workflow

[Multiple .sim Files]    [Wave Scatter Diagram]
   (per heading)              (Hs-Tp matrix)
        ↓                          ↓
[Extract Max Tensions]    [Probability Distribution]
        ↓                          ↓
[Operability Envelope]  →  [Weather Downtime Calc]
        ↓                          ↓
[Critical Headings]      [Annual Availability %]
        ↓                          ↓
[Combined HTML Report with Interactive Plots]

Configuration

Basic Operability Configuration

# configs/operability_config.yml

operability:
  # Input data
  simulation_directory: "results/.sim/"
  file_pattern: "mooring_heading_*.sim"

  # Tension extraction
  line_names:
    - "Mooring_Line_1"
    - "Mooring_Line_2"
    - "Mooring_Line_3"
    - "Mooring_Line_4"
  variable: "Effective Tension"
  statistic: "max"  # max, min, mean

  # Limits for envelope
  tension_limits:
    intact: 2500.0      # kN - intact condition limit
    damaged: 3000.0     # kN - damaged condition limit (typically higher)

  # Wave scatter for downtime
  wave_scatter:
    file: "data/wave_scatter_gom.csv"
    format: "hs_tp_matrix"  # or "hs_tp_list"

  # Output
  output:
    directory: "reports/operability/"
    report_name: "mooring_operability"
    format: "html"  # html, pdf

Advanced Configuration

# configs/operability_advanced.yml

operability:
  # Input data
  simulation_directory: "results/calm_operability/.sim/"
  file_pattern: "calm_hs*_tp*_dir*.sim"

  # Multi-line analysis
  line_groups:
    windward:
      lines: ["Leg_1", "Leg_2", "Leg_3"]
      critical_limit: 2000.0
    leeward:
      lines: ["Leg_4", "Leg_5", "Leg_6"]
      critical_limit: 2200.0

  # Heading analysis
  headings:
    start: 0
    end: 360
    step: 15
    critical_count: 5  # Top N critical headings to report

  # Envelope visualization
  envelope:
    polar_plot: true
    include_limits: true
    colorscale: "Viridis"
    show_critical_headings: true

  # Weather downtime
  downtime:
    operational_hours_per_year: 8760
    minimum_window_hours: 6  # Minimum weather window
    include_seasonal: true
    seasons:
      winter: [12, 1, 2]
      spring: [3, 4, 5]
      summer: [6, 7, 8]
      autumn: [9, 10, 11]

  # Output
  output:
    directory: "reports/operability/"
    report_name: "calm_operability_comprehensive"
    include_data_tables: true
    export_csv: true

Python API

Basic Operability Analysis

from digitalmodel.modules.orcaflex.operability_analysis import OperabilityAnalyzer

# Initialize analyzer
analyzer = OperabilityAnalyzer(
    simulation_directory="results/.sim/",
    output_directory="reports/operability/"
)

# Generate operability envelope
envelope = analyzer.generate_operability_envelope(
    line_names=["Mooring_Line_1", "Mooring_Line_2"],
    variable="Effective Tension",
    statistic="max",
    intact_limit=2500.0,
    damaged_limit=3000.0
)

# Save envelope plot
analyzer.save_envelope_plot(envelope, "operability_envelope.html")

Weather Downtime Calculation

from digitalmodel.modules.orcaflex.operability_analysis import OperabilityAnalyzer
import pandas as pd

analyzer = OperabilityAnalyzer(
    simulation_directory="results/.sim/",
    output_directory="reports/"
)

# Load wave scatter diagram
wave_scatter = pd.read_csv("data/wave_scatter.csv", index_col=0)

# Calculate weather downtime
downtime_results = analyzer.calculate_weather_downtime(
    wave_scatter=wave_scatter,
    operational_limit_hs=4.0,  # Operational Hs limit
    operational_limit_tp=12.0  # Operational Tp limit
)

print(f"Annual downtime: {downtime_results['annual_downtime_percent']:.1f}%")
print(f"Operational hours: {downtime_results['operational_hours']:.0f} hrs/yr")
print(f"Downtime days: {downtime_results['downtime_days']:.1f} days/yr")

Critical Headings Analysis

from digitalmodel.modules.orcaflex.operability_analysis import OperabilityAnalyzer

analyzer = OperabilityAnalyzer(
    simulation_directory="results/.sim/",
    output_directory="reports/"
)

# Identify critical headings
critical = analyzer.generate_critical_headings_report(
    line_names=["Leg_1", "Leg_2", "Leg_3", "Leg_4", "Leg_5", "Leg_6"],
    variable="Effective Tension",
    top_n=5,  # Top 5 most critical headings
    limit=2500.0
)

# Report format:
# critical = {
#     "headings": [45, 135, 225, 315, 0],
#     "max_tensions": [2450.2, 2380.5, 2350.1, 2290.8, 2250.3],
#     "utilization": [0.98, 0.95, 0.94, 0.92, 0.90],
#     "critical_lines": ["Leg_1", "Leg_3", "Leg_5", "Leg_2", "Leg_4"]
# }

for i, heading in enumerate(critical["headings"]):
    print(f"Heading {heading}°: {critical['max_tensions'][i]:.1f} kN "
          f"({critical['utilization'][i]*100:.1f}% utilization)")

Comprehensive Report Generation

from digitalmodel.modules.orcaflex.operability_analysis import OperabilityAnalyzer

analyzer = OperabilityAnalyzer(
    simulation_directory="results/.sim/",
    output_directory="reports/"
)

# Generate comprehensive HTML report with all analyses
report_path = analyzer.generate_comprehensive_report(
    line_names=["Leg_1", "Leg_2", "Leg_3", "Leg_4", "Leg_5", "Leg_6"],
    variable="Effective Tension",
    intact_limit=2500.0,
    damaged_limit=3000.0,
    wave_scatter_file="data/wave_scatter.csv",
    report_title="CALM Buoy Mooring Operability Assessment",
    include_envelope=True,
    include_critical_headings=True,
    include_weather_downtime=True
)

print(f"Report saved to: {report_path}")

Output Formats

Operability Envelope Plot

Interactive Plotly polar plot showing:

Maximum tension vs heading angle
Intact and damaged limit circles
Color-coded utilization zones
Hover tooltips with exact values

Critical Headings Table

| Rank | Heading (°) | Max Tension (kN) | Utilization (%) | Critical Line | Status | |------|-------------|------------------|-----------------|---------------|--------| | 1 | 45 | 2450.2 | 98.0 | Leg_1 | WARNING | | 2 | 135 | 2380.5 | 95.2 | Leg_3 | OK | | 3 | 225 | 2350.1 | 94.0 | Leg_5 | OK |

Weather Downtime Summary

{
  "annual_downtime_percent": 12.5,
  "operational_hours_per_year": 7665,
  "downtime_hours_per_year": 1095,
  "downtime_days_per_year": 45.6,
  "seasonal_breakdown": {
    "winter": {"downtime_percent": 25.3, "days": 23.1},
    "spring": {"downtime_percent": 10.2, "days": 9.3},
    "summer": {"downtime_percent": 5.1, "days": 4.7},
    "autumn": {"downtime_percent": 9.4, "days": 8.5}
  }
}

Wave Scatter Diagram Format

CSV Matrix Format

Tp\Hs,0.5,1.0,1.5,2.0,2.5,3.0,3.5,4.0
4,0.001,0.002,0.001,0.000,0.000,0.000,0.000,0.000
6,0.005,0.015,0.020,0.010,0.003,0.001,0.000,0.000
8,0.010,0.050,0.080,0.060,0.030,0.010,0.003,0.001
10,0.008,0.040,0.070,0.080,0.050,0.025,0.010,0.003
12,0.005,0.025,0.040,0.050,0.040,0.020,0.010,0.005
14,0.002,0.010,0.020,0.025,0.020,0.015,0.008,0.003

Values represent probability of occurrence (sum = 1.0).

Best Practices

Simulation Setup

Consistent headings - Use regular intervals (15° or 30°)
Sufficient sea states - Cover full scatter diagram range
Consistent naming - Include heading in filename
Complete simulations - Ensure all finish successfully

Limit Selection

Intact limit - Based on design code (e.g., 60% MBL)
Damaged limit - Account for redundancy (e.g., 80% MBL)
Include safety factors - Per API RP 2SK or DNV

Weather Downtime

Site-specific scatter - Use project metocean data
Operational limits - Define based on system capabilities
Weather windows - Consider minimum window requirements

Error Handling

try:
    envelope = analyzer.generate_operability_envelope(...)
except FileNotFoundError as e:
    print(f"Simulation files not found: {e}")
    print("Check simulation_directory and file_pattern")

except ValueError as e:
    print(f"Configuration error: {e}")
    print("Check line names and variable specifications")

Integration with Other Skills

With OrcaFlex Modeling

# 1. Run simulations for multiple headings
from digitalmodel.modules.orcaflex.universal import UniversalOrcaFlexRunner

runner = UniversalOrcaFlexRunner()
for heading in range(0, 360, 15):
    runner.run_single(f"mooring_heading_{heading}.yml")

# 2. Run operability analysis
from digitalmodel.modules.orcaflex.operability_analysis import OperabilityAnalyzer

analyzer = OperabilityAnalyzer(simulation_directory="results/.sim/")
analyzer.generate_comprehensive_report(...)

With Post-Processing

# Use OPP for detailed extraction, then operability for envelope
from digitalmodel.modules.orcaflex.opp import OrcaFlexPostProcess
from digitalmodel.modules.orcaflex.operability_analysis import OperabilityAnalyzer

# Extract detailed statistics
opp = OrcaFlexPostProcess()
stats = opp.extract_summary_statistics(...)

# Generate operability envelope
analyzer = OperabilityAnalyzer(...)
envelope = analyzer.generate_operability_envelope(...)

Related Skills

orcaflex-modeling - Run OrcaFlex simulations
orcaflex-post-processing - Extract results
orcaflex-extreme-analysis - Extreme value extraction
mooring-design - Mooring system design

References

API RP 2SK: Design and Analysis of Stationkeeping Systems
DNV-OS-E301: Position Mooring
ISO 19901-7: Stationkeeping Systems
Source: src/digitalmodel/modules/orcaflex/operability_analysis.py