name: catenary-riser description: Analyze catenary and lazy wave riser configurations for static shape, forces, and OrcaFlex model generation. Use for riser static configuration analysis, catenary force calculations, lazy wave design, and generating OrcaFlex models from catenary parameters. updated: '2026-01-07'

Catenary Riser Analysis Skill

Analyze catenary and lazy wave riser configurations for static shape, forces, tension distribution, and OrcaFlex model generation.

Version Metadata

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

Changelog

[1.0.0] - 2026-01-07

Added:

Initial version metadata and dependency management
Semantic versioning support
Compatibility information for Python 3.10-3.13

Changed:

Enhanced skill documentation structure

When to Use

Catenary riser static analysis
Lazy wave catenary design and optimization
Riser static configuration calculation
Catenary force and tension analysis
Generating OrcaFlex models from catenary geometry
Fatigue loading extraction from riser configurations
Pipe property calculations (buoyancy, effective weight)

Prerequisites

Python environment with digitalmodel package installed
Riser geometry and material properties
Environmental data (water depth, current if applicable)

Analysis Types

1. Simple Catenary Analysis

catenary:
  simple_catenary:
    flag: true
    geometry:
      top_end:
        x: 0.0
        z: 100.0
      touchdown:
        x: 500.0
        z: 0.0
    properties:
      outer_diameter: 0.2032
      wall_thickness: 0.0127
      steel_density: 7850
      internal_fluid_density: 800
      seawater_density: 1025
    output:
      shape_file: "results/catenary_shape.csv"
      forces_file: "results/catenary_forces.csv"
      plot_file: "results/catenary_plot.html"

2. Lazy Wave Catenary

catenary:
  lazy_wave:
    flag: true
    geometry:
      water_depth: 1500.0
      hang_off_angle: 8.0
      buoyancy_section:
        start_arc_length: 800.0
        end_arc_length: 1200.0
        buoyancy_factor: 1.5
      target_sag_bend_depth: 800.0
      target_hog_bend_depth: 600.0
    pipe_properties:
      outer_diameter: 0.273
      wall_thickness: 0.0159
    output:
      configuration_file: "results/lazy_wave_config.csv"
      plot_file: "results/lazy_wave_plot.html"

3. OrcaFlex Model Generation

catenary:
  orcaflex_model:
    flag: true
    catenary_config: "results/lazy_wave_config.csv"
    orcaflex_settings:
      line_name: "Riser1"
      segment_length: 5.0
      include_buoyancy_modules: true
    output:
      yml_file: "models/riser_model.yml"

Python API

Simple Catenary Equation

from digitalmodel.subsea.catenary.catenary_equation import CatenaryEquation
import numpy as np

catenary = CatenaryEquation()
top_end = (0.0, 100.0)
touchdown = (500.0, 0.0)

horizontal_tension = catenary.solve(
    top_end=top_end,
    bottom_end=touchdown,
    unit_weight=500.0
)

arc_lengths = np.linspace(0, catenary.total_length, 100)
x, z = catenary.get_shape(arc_lengths)
tensions = catenary.get_tension(arc_lengths)

Catenary Riser Analysis

from digitalmodel.subsea.catenary.catenary_riser import CatenaryRiser
from digitalmodel.subsea.catenary.pipe_properties import PipeProperties

pipe = PipeProperties(
    outer_diameter=0.2032,
    wall_thickness=0.0127,
    steel_density=7850,
    internal_fluid_density=800
)

riser = CatenaryRiser(pipe_properties=pipe)
results = riser.analyze(
    water_depth=1000.0,
    hang_off_angle=10.0,
    top_tension=1500e3
)

print(f"TDP position: x={results['tdp_x']:.1f}m")
print(f"Total length: {results['total_length']:.1f} m")

Lazy Wave Catenary

from digitalmodel.subsea.catenary.lazy_wave_catenary import LazyWaveCatenary

lazy_wave = LazyWaveCatenary()
config = {
    "water_depth": 1500.0,
    "hang_off_angle": 8.0,
    "buoyancy_section": {
        "start_length": 800.0,
        "end_length": 1200.0,
        "net_buoyancy": 300.0
    },
    "pipe_properties": pipe
}

results = lazy_wave.analyze(config)
sag_bend = results["sag_bend"]
hog_bend = results["hog_bend"]

OrcaFlex Model Building

from digitalmodel.subsea.catenary.orcaflex_model import OrcaFlexModelBuilder

builder = OrcaFlexModelBuilder()
builder.set_line_from_catenary(
    catenary_results=results,
    line_name="Riser1",
    segment_length=5.0
)
builder.add_buoyancy_section(
    start_arc_length=800.0,
    end_arc_length=1200.0,
    buoyancy_od=0.6
)
builder.export_yml("models/riser.yml")

Key Classes

Class	Purpose
`CatenaryEquation`	Mathematical catenary solver
`CatenaryRiser`	Main analysis orchestrator
`LazyWaveCatenary`	Dynamic catenary with buoyancy
`PipeProperties`	Material and geometric properties
`OrcaFlexModelBuilder`	Model export to OrcaFlex

Output Formats

Catenary Shape CSV

arc_length,x,z,tension,curvature,bend_moment
0.0,0.0,100.0,1523456.7,0.000123,1875.4
10.0,9.8,98.5,1518234.5,0.000145,2215.6

Best Practices

Consistent units - Use SI units (meters, Newtons)
Coordinate system - Z positive upward, origin at seabed
Segment resolution - Use small segments near critical points
Curvature check - Verify minimum bend radius constraints

Related Skills

orcaflex-modeling - Run OrcaFlex simulations
fatigue-analysis - Fatigue at critical locations
structural-analysis - Stress verification

References

API RP 2RD: Design of Risers for Floating Production Systems
DNV-OS-F201: Dynamic Risers

catenary-riser

Installation

Details

Usage

Skill Instructions

Catenary Riser Analysis Skill

Version Metadata

Changelog

[1.0.0] - 2026-01-07

When to Use

Prerequisites

Analysis Types

1. Simple Catenary Analysis

2. Lazy Wave Catenary

3. OrcaFlex Model Generation

Python API

Simple Catenary Equation

Catenary Riser Analysis

Lazy Wave Catenary

OrcaFlex Model Building

Key Classes

Output Formats

Catenary Shape CSV

Best Practices

Related Skills

References

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