catenary-riser

# Catenary Riser

## 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)

## Python API

### Simple Catenary Equation

```python
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,

*See sub-skills for full details.*
### Catenary Riser Analysis

```python
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
)

*See sub-skills for full details.*
### Lazy Wave Catenary

```python
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,

*See sub-skills for full details.*
### OrcaFlex Model Building

```python
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(

*See sub-skills for full details.*

## 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 |

## Related Skills

- [orcaflex/modeling](../orcaflex/modeling/SKILL.md) - Run OrcaFlex simulations
- [fatigue-analysis](../fatigue-analysis/SKILL.md) - Fatigue at critical locations
- [structural-analysis](../structural-analysis/SKILL.md) - Stress verification

## References

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

## Sub-Skills

- [Best Practices](best-practices/SKILL.md)

## Sub-Skills

- [Version Metadata](version-metadata/SKILL.md)
- [[1.0.0] - 2026-01-07](100-2026-01-07/SKILL.md)
- [1. Simple Catenary Analysis (+2)](1-simple-catenary-analysis/SKILL.md)
- [Catenary Shape CSV](catenary-shape-csv/SKILL.md)