vamseeachanta 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
digitalmodelpackage installed - Riser geometry and material properties
- Environmental data (water depth, current if applicable)
Python API
Simple Catenary Equation
from digitalmodel.marine_ops.marine_analysis.catenary import CatenarySolver, CatenaryInput
import numpy as np
catenary = CatenarySolver()
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
> **`CatenaryRiser` does not exist.** Build the configuration and call
> `CatenarySolver` directly. Do **not** reach for
> `digitalmodel.subsea.catenary_riser.LazyWaveAnalyzer`: it is **quarantined**
> (`tests/subsea/catenary_riser/test_lazy_wave_quarantine.py`) because it
> returned hardcoded fractions of water depth with buoyancy having no effect,
> and it now raises `NotImplementedError`.
```python
from digitalmodel.marine_ops.marine_analysis.catenary import CatenarySolver
from digitalmodel.infrastructure.base_solvers.marine.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
> Verified against this solver in an end-to-end engagement (aceengineer-agents
> `examples/lazy-wave-verification/`). Note `results.vertical_force` is
> **defective** — it returns `Fv + Fh`; the correct vertical component is
> `w · S_hangoff` (digitalmodel#2044).
```python
from digitalmodel.marine_ops.marine_analysis.catenary import (
LazyWaveSolver, LazyWaveConfiguration, derive_hangoff_bend_radius
)
lazy_wave = LazyWaveSolver()
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
> **`OrcaFlexModelBuilder` does not exist anywhere in `digitalmodel`.** The
> snippet below documents an intended capability that was never built. Treat it
> as a specification, not as runnable code, and build the OrcaFlex model through
> `digitalmodel.solvers.orcaflex` instead.
```python
# NOT RUNNABLE -- OrcaFlexModelBuilder does not exist. Specification only.
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)