viv-analysis

# Viv Analysis

## When to Use

- VIV analysis for risers and pipelines
- Natural frequency calculation for tubular members
- Vortex shedding frequency analysis
- VIV fatigue damage assessment
- Tubular member VIV screening
- Safety factor evaluation against VIV criteria

## Prerequisites

- Python environment with `digitalmodel` package installed
- Member geometry and material properties
- Current velocity profiles
- For risers: tension distribution along length

## Python API

### Natural Frequency Calculation

```python
from digitalmodel.subsea.viv_analysis.viv_analysis import VIVAnalysis
from digitalmodel.subsea.viv_analysis.viv_tubular_members import VIVTubularMembers

# Initialize analysis
viv = VIVAnalysis()

# Define member properties
member = {
    "length": 50.0,

*See sub-skills for full details.*
### Vortex Shedding Analysis

```python
# Vortex shedding frequency
diameter = 0.5  # meters
current_velocity = 1.5  # m/s
strouhal = 0.2

shedding_freq = viv.vortex_shedding_frequency(
    diameter=diameter,
    velocity=current_velocity,
    strouhal_number=strouhal

*See sub-skills for full details.*
### Tubular Member Analysis

```python
from digitalmodel.subsea.viv_analysis.viv_tubular_members import VIVTubularMembers

# Initialize tubular member analysis
tubular = VIVTubularMembers()

# Define member
member_props = {
    "name": "Brace1",
    "outer_diameter": 0.324,

*See sub-skills for full details.*
### VIV Fatigue Assessment

```python
from digitalmodel.subsea.viv_analysis.viv_fatigue import VIVFatigue

# Initialize VIV fatigue analysis
viv_fatigue = VIVFatigue()

# Calculate VIV-induced stress range
stress_range = viv_fatigue.calculate_stress_range(
    amplitude=0.5,  # VIV amplitude in diameters
    diameter=0.324,

*See sub-skills for full details.*

## Key Classes

| Class | Purpose |
|-------|---------|
| `VIVAnalysis` | Main VIV analysis router |
| `VIVTubularMembers` | Tubular member assessment |
| `VIVAnalysisComponents` | Component-level analysis |
| `VIVFatigue` | VIV-induced fatigue damage |

## Related Skills

- [catenary-riser](../catenary-riser/SKILL.md) - Riser configuration
- [fatigue-analysis](../fatigue-analysis/SKILL.md) - VIV fatigue damage
- [structural-analysis](../structural-analysis/SKILL.md) - Stress verification

## References

- DNV-RP-C205: Environmental Conditions and Environmental Loads
- DNV-RP-F105: Free Spanning Pipelines
- Blevins, R.D.: Flow-Induced Vibration

## 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. Natural Frequency Analysis (+3)](1-natural-frequency-analysis/SKILL.md)
- [Strouhal Number (+2)](strouhal-number/SKILL.md)
- [Complete VIV Screening Workflow](complete-viv-screening-workflow/SKILL.md)
- [Natural Frequencies JSON (+1)](natural-frequencies-json/SKILL.md)
- [Design Code References](design-code-references/SKILL.md)