hydrodynamics

name	hydrodynamics
description	Manage hydrodynamic coefficients, wave spectra, and environmental loading for vessel response analysis. Use for 6×6 matrix management, wave spectrum modeling, OCIMF loading calculations, and RAO interpolation.
type	reference
updated	2026-01-07
capabilities	[]
requires	[]
tags	[]
scripts_exempt	true
category	engineering
version	1.0.0

Hydrodynamics

When to Use

• 6×6 added mass and damping matrix management
• Wave spectrum modeling (JONSWAP, Bretschneider, PM)
• OCIMF wind and current loading calculations
• RAO interpolation and frequency-dependent coefficients
• Hydrodynamic coefficient database management
• Kramers-Kronig causality validation

Prerequisites

• Python environment with digitalmodel package installed
• Hydrodynamic coefficient data (from AQWA, WAMIT, etc.)
• Environmental data for wave/wind/current loading

Python API

Coefficient Database

from digitalmodel.hydrodynamics.coefficient_database import CoefficientDatabase

# Initialize database
db = CoefficientDatabase()

# Store coefficients
db.store(
    vessel_name="FPSO",
    frequency=0.1,

*See sub-skills for full details.*
### Frequency-Dependent Matrices

```python
from digitalmodel.hydrodynamics.freq_dependent import FrequencyDependentMatrix

# Initialize with frequency-dependent data
fdm = FrequencyDependentMatrix()
fdm.load("hydro_data.json")

# Interpolate to specific frequency
A_interp = fdm.interpolate_added_mass(frequency=0.15)
B_interp = fdm.interpolate_damping(frequency=0.15)

# Get infinite frequency added mass
A_inf = fdm.get_infinite_frequency_added_mass()

Wave Spectra

from digitalmodel.hydrodynamics.wave_spectra import WaveSpectra

# Create JONSWAP spectrum
spectrum = WaveSpectra()
frequencies, S = spectrum.jonswap(
    hs=3.5,       # Significant wave height (m)
    tp=10.0,      # Peak period (s)
    gamma=3.3,    # Peakedness parameter
    freq_min=0.02,

*See sub-skills  full details.*


```python
 digitalmodel.hydrodynamics.ocimf_loading  OCIMFLoading


ocimf = OCIMFLoading()


vessel = {
    : ,
    : ,

*See sub-skills  full details.*


```python
 digitalmodel.hydrodynamics.interpolator  CoefficientsInterpolator


interp = CoefficientsInterpolator()


interp.load_raos()



*See sub-skills  full details.*


```python
 digitalmodel.hydrodynamics.validation  HydroValidator


validator = HydroValidator()


validator.load_coefficients()



*See sub-skills  full details.*


```python
 yaml
 digitalmodel.marine_ops.marine_analysis  (
    RAODataValidators,
    VesselType,
    DisplacementRAOQualityReport
)
 digitalmodel.marine_ops.marine_analysis.rao_quality_report  RAOQualityReportGenerator



*See sub-skills  full details.*



| Class | Purpose |
|-------|---------|
| `CoefficientDatabase` | Coefficient storage  retrieval |
| `FrequencyDependentMatrix` | × matrix interpolation |
| `WaveSpectra` | Spectrum generation (JONSWAP, PM, etc.) |
| `OCIMFLoading` | OCIMF wind/current calculations |
| `CoefficientsInterpolator` | 2D interpolation (freq × direction) |
| `HydroValidator` | Kramers-Kronig  matrix validation |
| `RAODataValidators` | RAO quality checks (phase, peaks, vessel ) |
| `RAOQualityReportGenerator` | HTML/CSV quality report generation |



- [diffraction-analysis](../diffraction-analysis/SKILL.md) - **Master skill**   diffraction workflows
- [aqwa-analysis](../aqwa-analysis/SKILL.md) - Extract coefficients  AQWA
- [bemrosetta](../bemrosetta/SKILL.md) - AQWA → OrcaFlex conversion  QTF  mesh support
- [orcaflex/modeling](../orcaflex/modeling/SKILL.md) - Apply  OrcaFlex models
- [viv-analysis](../viv-analysis/SKILL.md) - Hydrodynamic coefficient usage



- DNV-RP-C205: Environmental Conditions  Environmental Loads
- OCIMF: Mooring Equipment Guidelines
- Newman, J.N.: Marine Hydrodynamics



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



- [Version Metadata](version-metadata/SKILL.md)
- [[] - -01-07](--01-07/SKILL.md)
- [ Coefficient Database Management (+)](-coefficient-database-management/SKILL.md)
- [Wave Spectrum Types](wave-spectrum-types/SKILL.md)
- [Coefficient Database JSON (+)](coefficient-database-json/SKILL.md)