orcaflex-modal-analysis

name	orcaflex-modal-analysis
description	Perform modal and frequency analysis on OrcaFlex models to extract natural frequencies, mode shapes, and identify dominant DOF responses. Use for VIV assessment, resonance identification, and structural dynamics characterization.
type	reference
version	1.0.0
updated	"2026-01-17T00:00:00.000Z"
category	engineering
triggers	["modal analysis","natural frequency","mode shapes","frequency analysis","eigenvalue analysis","resonance identification","DOF analysis","structural dynamics"]
capabilities	[]
requires	[]
tags	[]
scripts_exempt	true

Orcaflex Modal Analysis

When to Use

• Extract natural frequencies from OrcaFlex models
• Calculate mode shapes for risers, lines, and structures
• Identify dominant degrees of freedom in each mode
• Filter modes by specific DOF (heave, surge, pitch, etc.)
• VIV susceptibility screening (compare natural frequencies to shedding frequencies)
• Resonance identification for environmental loading
• Batch processing multiple water depths or configurations

Prerequisites

• OrcaFlex license (for OrcFxAPI)
• Python environment with digitalmodel package installed
• Model files (.dat, .yml, or .sim)

Python API

Basic Modal Analysis

from digitalmodel.orcaflex.orcaflex_modal_analysis import OrcModalAnalysis

# Initialize analyzer
modal = OrcModalAnalysis()

# Configure analysis
cfg = {
    "default": {
        "Analysis": {

*See sub-skills for full details.*
### Direct OrcFxAPI Usage

```python
import OrcFxAPI

# Load model and calculate statics
model = OrcFxAPI.Model()
model.LoadData("model.yml")
model.CalculateStatics()

# Configure modal analysis
spec = OrcFxAPI.ModalAnalysisSpecification(

*See sub-skills for full details.*
### Extract Dominant DOFs

```python
from digitalmodel.orcaflex.orcaflex_modal_analysis import OrcModalAnalysis
import pandas as pd

modal = OrcModalAnalysis()

# After running analysis, get summary
all_modes_summary_df = modal.all_file_summary["Case1"]

# Filter modes dominated by specific DOF

*See sub-skills for full details.*

## Related Skills

- [orcaflex-modeling](../orcaflex-modeling/SKILL.md) - Run OrcaFlex simulations
- [viv-analysis](../viv-analysis/SKILL.md) - VIV susceptibility assessment
- [orcaflex-static-debug](../orcaflex-static-debug/SKILL.md) - Static convergence troubleshooting



- OrcFxAPI Modal Analysis: Orcina Documentation
- DNV-RP-C205: Environmental Conditions  Environmental Loads
- API RP 2RD: Design of Risers  Floating Production Systems
- Source: `src/digitalmodel/modules/orcaflex/orcaflex_modal_analysis.py`
- Config: `src/digitalmodel/base_configs/modules/orcaflex/orcaflex_modal_analysis.yml`



- [Basic Modal Analysis (+)](basic-modal-analysis/SKILL.md)
- [Model Preparation (+)](model-preparation/SKILL.md)



- [Version Metadata](version-metadata/SKILL.md)
- [[] - -01-](--01-/SKILL.md)
- [ Static Equilibrium → Modal Analysis](-static-equilibrium-modal-analysis/SKILL.md)
- [Mode Shapes CSV (+)](mode-shapes-csv/SKILL.md)
- [DOF Percentage Calculation (+)](dof-percentage-calculation/SKILL.md)
- [Common Errors  Fixes (+)](common-errors--fixes/SKILL.md)
- [Expected Frequency Ranges (+)](expected-frequency-ranges/SKILL.md)
- [With VIV Analysis (+)](-viv-analysis/SKILL.md)