name: bemrosetta description: BEMRosetta hydrodynamic coefficient converter - AQWA to OrcaFlex workflow with QTF and mesh support version: 1.0.0 updated: 2026-01-27 category: offshore-engineering triggers:

• bemrosetta
• hydrodynamic conversion
• AQWA to OrcaFlex
• coefficient converter
• QTF conversion
• mesh format conversion
• GDF to STL
• panel mesh
• Kramers-Kronig
• causality check

BEMRosetta Integration Skill

Version

• Skill Version: 1.0.0
• Module Version: 1.0.0
• Python: 3.11+
• Dependencies: numpy, scipy, click, pydantic, loguru

Changelog

1.0.0 (2026-01-27)

• Initial release
• AQWA parser for .LIS files
• QTF parser for second-order forces
• OrcaFlex converter (YAML, CSV)
• Mesh handlers (GDF, DAT, STL)
• Coefficient and causality validators
• Click-based CLI

When to Use

Use this skill when you need to:

1. Convert AQWA outputs to OrcaFlex format

   • Parse AQWA .LIS diffraction analysis files
   • Export to OrcaFlex-compatible YAML and CSV

2. Handle QTF (second-order forces) data

   • Parse QTF files for sum/difference frequency forces
   • Export QTF to OrcaFlex format

3. Convert mesh formats

   • Convert between GDF (WAMIT), DAT (AQWA/NEMOH), STL formats
   • Validate mesh quality

4. Validate hydrodynamic coefficients

   • Check matrix symmetry and positive definiteness
   • Verify Kramers-Kronig causality relations

Agent Capabilities

The BEMRosetta skill enables agents to:

Parsing

• Parse AQWA .LIS files extracting RAOs, added mass, damping
• Parse QTF files for second-order wave forces
• Extract solver metadata (version, water depth, frequencies, headings)

Conversion

• Convert to OrcaFlex vessel type YAML
• Export coefficient CSV files
• Export QTF data in OrcaFlex format

Mesh Processing

• Read/write WAMIT GDF format
• Read/write AQWA/NEMOH DAT format
• Read/write STL format (ASCII and binary)
• Calculate mesh quality metrics

Validation

• Coefficient symmetry checks
• Positive definiteness verification
• Physical limits validation
• Kramers-Kronig causality checking

Prerequisites

# Module is included in digitalmodel package
uv pip install -e .

# Verify installation
bemrosetta status

CLI Commands

# Convert AQWA to OrcaFlex
bemrosetta convert analysis.LIS -o ./output

# Convert with QTF data
bemrosetta convert analysis.LIS --qtf analysis.QTF -o ./output

# Display file information
bemrosetta info analysis.LIS

# Validate coefficients
bemrosetta validate analysis.LIS --strict --causality

# Convert mesh formats
bemrosetta convert-mesh input.gdf -o output.stl
bemrosetta convert-mesh input.dat -o output.gdf

# Validate mesh quality
bemrosetta validate-mesh hull.gdf --check-normals

# Show module status
bemrosetta status

Python API

Basic Workflow

from digitalmodel.modules.bemrosetta import (
    AQWAParser,
    OrcaFlexConverter,
    validate_coefficients,
)

# Parse AQWA results
parser = AQWAParser()
results = parser.parse("analysis.LIS")

# Access metadata
print(f"Vessel: {parser.metadata.vessel_name}")
print(f"Water depth: {parser.metadata.water_depth}")
print(f"Frequencies: {parser.metadata.frequency_count}")

# Validate coefficients
report = validate_coefficients(results, strict=True)
if not report.is_valid:
    print(f"Errors: {report.errors}")

# Convert to OrcaFlex format
converter = OrcaFlexConverter(output_dir="./output")
converter.convert(results)

QTF Handling

from digitalmodel.modules.bemrosetta import QTFParser, OrcaFlexConverter

# Parse QTF file
qtf_parser = QTFParser()
qtf_data = qtf_parser.parse("analysis.QTF")

print(f"QTF type: {qtf_data.qtf_type}")
print(f"Frequencies: {qtf_data.n_frequencies_1} x {qtf_data.n_frequencies_2}")

# Include QTF in conversion
converter = OrcaFlexConverter(output_dir="./output")
converter.set_qtf_data(qtf_data)
converter.convert(results)

Mesh Conversion

from digitalmodel.modules.bemrosetta import (
    GDFHandler, DATHandler, STLHandler, convert_mesh
)

# Read GDF mesh
handler = GDFHandler()
mesh = handler.read("hull.gdf")

# Check quality
report = handler.validate_mesh(mesh)
print(f"Panels: {report.n_panels}")
print(f"Quality score: {report.quality_score}/100")

# Convert to STL
convert_mesh("hull.gdf", "hull.stl")

Causality Validation

from digitalmodel.modules.bemrosetta import (
    CoefficientValidator,
    CausalityChecker,
)

# Coefficient validation
validator = CoefficientValidator(
    check_symmetry=True,
    check_positive_definite=True,
    tolerance=0.01,
)
report = validator.validate(results)

# Kramers-Kronig causality check
checker = CausalityChecker(tolerance=0.1)
kk_report = checker.validate(results)
for key, error in kk_report.info.items():
    if error and error > 0.1:
        print(f"Warning: {key} KK error = {error:.2%}")

Key Classes

Data Models

Best Practices

1. Always validate before conversion

   report = validate_coefficients(results, strict=True)
   if not report.is_valid:
       raise ValueError(f"Invalid coefficients: {report.errors}")
   

2. Check mesh quality before use

   report = handler.validate_mesh(mesh)
   if report.quality_score < 70:
       print("Warning: Low mesh quality")
   

3. Use native parsers for reliability

   • Native Python parsers don't require BEMRosetta executable
   • BEMRosetta executable provides extended features when available

4. Handle missing data gracefully

   warnings = converter.validate_input(results)
   for w in warnings:
       logger.warning(w)
   

Integration with Other Modules

With diffraction module

from digitalmodel.modules.diffraction import OrcaFlexExporter
from digitalmodel.modules.bemrosetta import AQWAParser

# BEMRosetta uses diffraction module schemas
parser = AQWAParser()
results = parser.parse("analysis.LIS")  # Returns DiffractionResults

# Can use existing OrcaFlexExporter
exporter = OrcaFlexExporter(results, output_dir)
exporter.export_all()

With hydrodynamics module

from digitalmodel.modules.hydrodynamics import CoefficientDatabase

# Store parsed coefficients in database
db = CoefficientDatabase()
db.store(results.added_mass, results.damping)

Error Handling

from digitalmodel.modules.bemrosetta import (
    BEMRosettaError,
    ParserError,
    ConverterError,
    MeshError,
)

try:
    results = parser.parse("analysis.LIS")
except ParserError as e:
    print(f"Parse error: {e}")
    print(f"File: {e.context.get('file_path')}")
except BEMRosettaError as e:
    print(f"BEMRosetta error: {e}")

Related Skills

• aqwa-analysis - AQWA .LIS processing and RAO extraction
• orcawave-analysis - OrcaWave diffraction/radiation analysis
• orcawave-to-orcaflex - OrcaWave to OrcaFlex conversion
• orcaflex-rao-import - Multi-format RAO import
• hydrodynamics - 6x6 matrices and wave spectra
• diffraction-analysis - Master skill for diffraction workflows

References

• BEMRosetta GitHub
• Module README
• OrcaFlex Documentation