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Octo × Open-source software PT Request an assessment

Octo for naval and offshore open-source software

From the hull in waves to the mooring line, on Linux.

OpenFOAM, Capytaine, NEMOH, MoorDyn, MoorPy, OpenFAST, meshmagick and FreeCAD with the Ship workbench are open source, and most of them run in batch. Octo can write the scripts that vary speed, draft or frequency, launch the cases, gather the results and log each run, with everything prepared for human review. The naval engineer decides what holds for the project.

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Floating hull on waves, with mooring lines to the seabed; from the center, Octo sends flows that become hydrodynamic coefficients, RAO and tension per line Nemoh.cal · 0/U WATERLINE MOORING SEABED A · B hull.nc RAO heave × ω TENSION · FAILED solver casos/calado_8m OCTO × OPEN-SOURCE SOFTWARE LINUX · BATCH NV-08
Capytaine 3.0.0Apache 2.0since version 3
NEMOH v3.0.3QTF2nd-order loads
OpenFOAM v14DTCHullready-made hull in the tutorials
Sources26listed at the end of the page
01

What Octo does with open-source software.

Six possible deliverables, drawn from the research. In all of them, a naval engineer decides and validates; Octo can take on the work of setting up, running and organizing.

Case series

It can write the script that varies speed, draft, wave heading or frequency and generates the case folders. For example, a speed series on the OpenFOAM v14 DTCHull hull, with foamDictionary, or a frequency range in Capytaine 3.

Deliverable: script + case folders

Batches with nobody at the menu

It can launch the cases from the command line (NEMOH's preProc, solver and postProc, OpenFOAM's Allrun), check that each one produced its output files and set aside the ones that failed, without hiding any.

Deliverable: case queue + list of what failed

Organized results

It can gather added mass, damping, RAO (response amplitude operator), hull forces and line tensions in CSV or a spreadsheet, with charts that compare the variants.

Deliverable: consolidated CSV + charts

Formats converted and compared

It can move meshes and coefficients from one format to another with meshmagick and BEMRosetta, and set up the comparison between two BEM (boundary element method) programs or two meshes for the engineer to analyze. Converting a format does not validate the result.

Deliverable: converted files + comparison

Mooring step by step

With the MoorDyn Python module, it can advance the line system in time and record the maximum tension of each line. With MoorPy, it can compute quasi-static equilibrium and stiffness for preliminary sizing.

Deliverable: tension per line + stiffness

A study that can be redone

Checks mesh normals, the hull cut at the waterline, units and axis and phase conventions before running, and logs the version of each tool and the exact command of each run.

Deliverable: log of assumptions, versions and commands
02

Eight arms, one open study.

The same Octo cycle, applied to free hydrodynamics and mooring tools. Each arm has a narrow role; the one who decides is the engineer in charge.

  1. Discovery

    Maps what is already used

    Which commercial programs the team uses, for which stage, and which open tool does the same job. It separates the preliminary study from what goes for approval, which stays with qualified people, the classification society and the maritime authority.

  2. Data

    Defines the exchange formats

    Mesh in NEMOH or WAMIT format, coefficients in Capytaine NetCDF (.nc), OpenFOAM text dictionaries and CSV for tables. One name per case, one folder per run.

  3. Security

    Reads the exact license

    GPL v3 for NEMOH, meshmagick and BEMRosetta; Apache 2.0 for Capytaine only from version 3; 3-clause BSD for MoorDyn. Before embedding anything in a product, the decision belongs to legal. Sending controlled data (ITAR/EAR) to any external service, including AI, must first be assessed by the client's compliance team.

  4. Architecture

    Builds the chain

    Proposes one possible setup: mesh (Gmsh or FreeCAD), check (meshmagick), coefficients (Capytaine or NEMOH), conversion (BEMRosetta) and time-domain simulation with mooring (OpenFAST with MoorDyn). It is a proposal, not a documented standard.

  5. Development

    Writes the scripts

    Uses each tool's documented API and flags what it could not find in the documentation. In Capytaine 3, meshes and bodies are no longer modified in place, and scripts written for 2.x may need adjusting.

  6. Review

    Checks against the reference

    Before the client's own case, it runs the project's test cases: NEMOH's TestCases/ (make run_1_cylinder), HAMS's CertTest/. Then it runs a few cases and checks the generated file, not the success message.

  7. Release

    Runs the approved batch

    With your OK, it runs the whole matrix, separates what produced results from what failed and returns the list, without hiding any failed case.

  8. Documentation

    Records what applies

    Version of each tool, command of each run, model assumptions and what was confirmed on the team's installation. The next study starts ready.

Octo prepares and runs for human review. The one who says whether the result holds for the project is the naval engineer; approval belongs to qualified people, the classification society and the maritime authority.

03

Each task, its own tool.

The table Octo uses to choose. Below, the equivalence with commercial tools: by function, not by qualification.

TaskOpen-source tool
Calm-water hull resistance, with CFD (computational fluid dynamics)OpenFOAM (DTCHull as a starting point)
Hull in waves and floating body in CFDOpenFOAM (DTCHullWave, floatingObjectWaves); olaFlow for waves
Added mass, damping, excitation and RAO (1st order)Capytaine or NEMOH; HAMS/pyHAMS
2nd-order loads (QTF, quadratic transfer function)NEMOH v3
Convert, check and fix a hull meshmeshmagick; Gmsh to generate
Compare BEM results between programs and convert formatsBEMRosetta
Dynamic time-domain mooringMoorDyn
Quasi-static mooring, stiffness and preliminary sizingMoorPy
Coupled floating wind platformOpenFAST (+ MoorDyn-F); RAFT in the frequency domain
Wave energy converterWEC-Sim (on MATLAB)
Hull form, hydrostatics and preliminary GZ curve (righting arm)FreeCAD + Ship; FREE!ship Plus
Seakeeping by strip theoryPDStrip
CommercialClosest open toolWhat is missing
WAMIT, Ansys AQWA (diffraction and radiation)Capytaine, NEMOH, HAMSIntegrated interface, support, validation track record with classification societies
OrcaFlex, SIMA (mooring and risers)MoorDyn, MoorPy, OpenFASTFull riser scope, integrated fatigue, component library, interface
STAR-CCM+, Fidelity Fine Marine, SHIPFLOW (naval CFD)OpenFOAMAutomatic hull mesher, ready-made towing and self-propulsion workflows, support
Maxsurf, NAPA (form and hydrostatics)FreeCAD + Ship, FREE!ship PlusDamage stability, built-in class rules, integration with structure and production
Approved loading computerNoneClassification society approval for use on board
04

From a script to a chained study.

Three steps. Each one only makes sense after the previous one has shown results on your team.

A proposal, not a promise

1 Today

Scripts on demand

On a Linux machine, the engineer asks for the study in engineering language and gets the script and the results to review.

  • “Hull coefficients from 0.2 to 2 rad/s in five headings” becomes a Capytaine script
  • The project's test case run before the client's own case
  • Consolidated CSV and a list of what failed
Goal: setting up cases leaves the team's hands
2 Next

Case queue

The batches start running in a queue, in parallel, over the approved study matrix.

  • NEMOH by case folder, OpenFOAM by dictionaries, MoorDyn by script
  • A failed case comes back with another adjustment or goes to a person
  • Run report with versions and commands
Goal: the team reviews the report instead of setting up cases
3 Later

Linked chain

The tools linked in a single study, from the hull mesh to the mooring.

  • Gmsh → meshmagick → Capytaine or NEMOH → BEMRosetta → OpenFAST with MoorDyn
  • Systematic comparison between two BEM programs
  • Axis and phase conventions fixed and checked on every run
Goal: the preliminary study becomes a company process
05

Confirmed by a source.

Every point below has a source published by the vendor, by the project or by the responsible agency. The sources are in the next section.

6

points with a published source, each with its reference shown alongside.

ConfirmedProjects alive in 2026
OpenFOAM v14 (Jul 14, 2026), Capytaine 3.0.0 (Aug 21, 2026), FreeCAD 1.1.4 (Sep 28, 2026), MoorDyn 2.7.2 (Oct 6, 2026) and BEMRosetta “2026_Nov” (Oct 21, 2026).Source: download page, PyPI or the GitHub/GitLab API of each project, consulted on Oct 28, 2026
ConfirmedCapytaine is Apache 2.0 only from version 3
The 3.0.0 notes say that code coming from GPL software was removed and that the contributors agreed to the change. Versions 2.x had another license; check which one is installed before embedding it in a product.Source: version 3.0.0 notes and the Capytaine repository
ConfirmedNEMOH is GPL v3 in the current repository
The LICENSE.txt on GitLab is GPL v3. The old GitHub repository is archived and shows up as Apache 2.0 in automatic detection; the current repository's license is the one that counts.Source: gitlab.com/lheea/Nemoh and github.com/LHEEA/Nemoh
ConfirmedReady-made naval cases in OpenFOAM v14
The tutorials/incompressibleVoF/ folder includes DTCHull, DTCHullMoving, DTCHullProp, DTCHullWave, floatingObject and floatingObjectWaves. In DTCHull, the speed is in 0/U (UMean 1.668).Source: OpenFOAM-14 repository on GitHub
ConfirmedProjects with little activity
PDStrip at rev27, from 05/2006; HAMS with no releases and last commit on Sep 8, 2023; olaFlow with its most recent release from 2018; Ship workbench with last commit on Jul 4, 2025.Source: SourceForge and the GitHub API, consulted on Oct 28, 2026
ConfirmedDELFTship Free is free of charge, but not open source
The vendor's page says it is free, with no feature or time limit, and does not publish the code.Source: delftship.net, downloads page
06

What Octo does, and what stays with you.

Octo prepares everything, but it does not sign. The document of record stays with whoever is accountable for it.

Octo prepares

Surveys, calculates, organizes and produces the documents: spreadsheets, reports, lists and drafts.

Deliverable: material ready to check

Your team checks

The licensed professional checks what Octo delivered before signing. If something doesn't add up, it goes back to Octo with the correction.

Step: checked by the person who signs

Who signs

Octo does not sign. Designs, technical reports, ART/RRT, statements of account and any official document are still signed by the licensed professional at the company or agency: here, the naval engineer in charge and the classification society.

Signature: naval engineer and classification society
07

Sources.

Sites, documentation, repositories and packages published by each project, consulted on Oct 28, 2026.

Your naval study, on Linux.

The assessment starts by listing the tools your team uses and the studies that repeat, without changing anything. Octo proposes a map of what can run on open-source software, with the licenses and limits of each tool, and you decide with that in hand.

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